Pulmonary fibrosis is a progressively aggravating lethal disease that is a serious public health concern. Although the incidence of this disease is increasing, there is a lack of effective therapies. In recent years, the pathogenesis of pulmonary fibrosis has become a research hotspot. p53 is a tumor suppressor gene with crucial roles in cell cycle, apoptosis, tumorigenesis, and malignant transformation. Previous studies on p53 have predominantly focused on its role in neoplastic disease. Following in-depth investigation, several studies have linked it to pulmonary fibrosis. This review covers the association between p53 and pulmonary fibrosis, with the aim of providing novel ideas to improve the clinical diagnosis, treatment, and prognosis of pulmonary fibrosis. Pulmonary fibrosis is a group of chronic, irreversible, and fatal interstitial lung diseases that occur mostly in middle-aged and elderly people . It mainβ1 (TGF-β1), tumor necrosis factor-α (TNF-α), and platelet-derived growth factor (PDGF) [It is currently accepted that the development and progression of pulmonary fibrosis are attributable to aberrant repair following repeated alveolar epithelial cell (AEC) injuries in response to various stimuli . The injr (PDGF) –8. Theser (PDGF) . This ler (PDGF)  . Nine point mutations were found in ten lung tissue samples. Most of the mutations occurred in the central area of the p53 gene . In anotβ1, to accelerate the EMT process and the proliferation of lung fibroblasts. This leads to the secretion of more collagen, which further accelerates pulmonary fibrosis. Many preliminary studies of pulmonary fibrosis have utilized this model [Some research studies have addressed the relationship between p53 and pulmonary fibrosis. Of the numerous methods to produce in vivo models of pulmonary fibrosis, the most common method is the injection of drugs, including bleomycin (BLM), amiodarone, and asbestos . A singlis model , 34. Folis model . In otheis model . This fiCell apoptosis is a type of programmed cell death and a key process that regulates homeostasis at the organizational, tissue, and internal environment level . There aδ and many other proteins that are involved in DNA synthesis to promote DNA synthesis. p21 directly inhibits DNA synthesis by competing with PCNA to bind with other DNA synthesis proteins [Researchers have constructed a mouse model of pulmonary fibrosis using a one-off intratracheal instillation of BLM. The results showed that apoptosis of type II AECs in the lung tissues of mice with pulmonary fibrosis was clearly enhanced, whereas the expression of the p53 protein was markedly increased. In contrast, knockout of the p53 protein effectively attenuated pulmonary fibrosis, and the extent of type II alveolar epithelial cell (AECII) apoptosis was also markedly alleviated, suggesting that the p53 protein probably accelerated the development and progression of pulmonary fibrosis by inducing AEC apoptosis . In a clproteins . Many stproteins . The afoIn addition, some studies have documented that the p53 protein could induce apoptosis in lung fibroblasts and myofibroblasts during the progression of pulmonary fibrosis, which may further delay the progression of pulmonary fibrosis. The effects of astaxanthin on myofibroblast apoptosis were also studied. The results indicated that astaxanthin could induce myofibroblast apoptosis through the activation of the mitochondrial apoptosis pathway. Further studies have confirmed the critical role of the p53 protein in this process . In anotβ-galactosidase , telomeres and telomerase, senescence-related heterochromatin foci, and senescence-associated secretory phenotype (SASP). Among these, β-gal is detected earliest and used most commonly as a senescence marker. This lysosome-derived enzyme increases lysosomal biosynthesis in senescent cells [Aging is an inhibited state of cell proliferation, in which the cell cycle is arrested in phase G0 or G1 . Morpholnt cells –53. It iRecent studies have shown that the aging-related secretory phenotype, telomere injury, epigenetic changes, mitochondrial autophagy injury, and other pathological processes are probably involved in the occurrence and development of cell aging . In an iβ-galactosidase in A549 cells was markedly enhanced, and that of the p53 protein was also clearly increased in a concentration-dependent manner, suggesting that p53 promoted AEC aging and accelerated the progression of pulmonary fibrosis [α (INF-α), and other related cytokines. Such cytokines can bind to the corresponding receptors on the membrane, leading to the activation of aging-related signals by p53 [A mouse model of pulmonary fibrosis was constructed by the administration of BLM to investigate the correlation between p53 and collagen deposition. The results showed that collagen deposition and p53 protein expression in BLM-induced mice was significantly enhanced compared with that in WT mice. To confirm the mechanism underlying AEC aging, A549 cells were treated with BLM. It was found that the expression of the aging-related marker fibrosis . It is rs by p53 .β-galactosidase was enhanced significantly, indicating obvious aging, in which the aging-related proteins p53, p21, and p16 played a crucial role [The effect of p53 on the regulation of lung fibroblast aging has been confirmed in a clinical study in which lung tissue was collected from patients with IPF and compared with tissues from healthy lung tissue. The results showed that the telomeres of lung fibroblasts in the lung tissue of patients with IPF were markedly shortened, and the expression of ial role . Cyclooxial role , 63. Ourial role . Interleial role   to inhibit nuclear factor E2-related factor 2- (Nrf2-) induced gene expression [Given the broader understanding of p53, it was found that the p53 protein has the dual functions of oxidation and antioxidation, depending on the degree of oxidative stress . In resppression , 77  or small mother against decapentaplegic3 (Smad3) at the carboxyl terminal, and is then translocated into the nucleus by forming a trimer with small mother against decapentaplegic4 (Smad4). After nuclear translocation, small mother against decapentaplegics (Smads) then bind to other transcription factors to regulate the expression of EMT-related genes, leading to the dysfunction of cellular junctions, cytoskeletal rearrangement, and enhancement of cell migration and cell invasion, and eventually to EMT [Recent studies have shown the close correlation between EMT and the development and progression of pulmonary fibrosis . In respy to EMT .α-SMA), a marker protein for EMT, was significantly enhanced, suggesting that the EMT process had been initiated. Further studies found that p53 probably participated in the entire EMT process. BLM promoted the phosphorylation of Ser15 in the p53 protein, inhibiting the binding of MDM2, a negative regulator, to p53, and promoting the EMT process [β1, and found reduced expression of the p53 protein. It is assumed that p53 inhibits the process of EMT. The difference between studies is probably related to the following factors. Although the two models are in vitro EMT models, they are two different models. Direct disruption of A549 cells with BLM not only leads to EMT but also to pathological processes related to cell injury. However, it still remains unknown which process is dominant. In addition, both experiments were in vitro tests and could, therefore, not simulate the complete internal environment. Therefore, further experiments are required to validate the functional role of p53 in EMT.Yamamoto et al. treated A549 cells with BLM and found that the morphology of A549 cells changed greatly. Meanwhile, the expression of alpha-smooth muscle actin , and pulmonary function tests, as well as bronchoscopy or lung biopsy if necessary . SerologThe establishment of a pulmonary fibrosis model by intratracheal instillation of BLM in p53 gene knockout and WT mice revealed significantly less collagen deposition in the lung tissue of p53 gene knockout mice and significantly reduced pulmonary fibrosis . These oThe weight of the evidence supports the hypothesis that the expression levels of p53 demonstrate a positive correlation with the severity of pulmonary fibrosis. However, p53 has various roles that are specific for different cells and have different mechanisms of action. During the progression of pulmonary fibrosis, an increase in p53 can promote AEC apoptosis, induce aging, aggravate oxidative injury, promote the progression of EMT, and accelerate the development of pulmonary fibrosis in terms of AECs. For lung fibroblasts, an increase in p53 can promote the apoptosis of lung fibroblasts, aggravate oxidative stress, and delay the development of pulmonary fibrosis. Meanwhile, increased p53 can also induce the aging of lung fibroblasts. This diversity makes it difficult to further clarify the regulatory mechanism of p53 in pulmonary fibrosis and to discover the corresponding drug treatment. Thus, for future treatment of pulmonary fibrosis, the targeted expression of p53 in different cells of lung tissues is a likely direction for study future studies which need to further focus on the following points.The data from most of the current studies support the view that damage to AECs initiates pulmonary fibrosis and drives its development. The ultimate pathological change in pulmonary fibrosis is the massive proliferation of lung fibroblasts and copious secretion of collagen. Thus, is the damage to AECs or the proliferation of lung fibroblasts more important in the overall process of pulmonary fibrosis? Although AECs may be the most important, this view is speculative, with a dearth of valid confirmatory evidence.p53 has different mechanisms of action for AECs and lung fibroblasts. This is a challenge for the development of drug therapies for pulmonary fibrosis that target p53. We believe that the current research on the underlying mechanisms of p53 in pulmonary fibrosis has been relatively superficial. Most studies have not addressed the function of the p53 protein. For example, the molecular mechanisms used by p53 to regulate AECs and lung fibroblasts are unknown. Furthermore, the p53 phosphorylation sites used to regulate apoptosis and senescence in AECs and lung fibroblasts are unknown. These issues must be clarified to further understand the role of p53 in the regulation of pulmonary fibrosis.There have been few studies of drugs targeting p53 for the treatment of pulmonary fibrosis. However, many drugs that target p53 have been developed as cancer therapeutics. It is conceivable that these drugs may be beneficial for the treatment of pulmonary fibrosis.Since p53 has different mechanisms of action in different cells, two points are crucial for the development of new drugs targeting p53 for the treatment of pulmonary fibrosis. First, we need to clarify whether the drug primarily targets AECs or lung fibroblasts. Second, we need to identify the signal transduction mechanism through which the drug exerts its effects. Targeting specific cells and specifically modulating p53 expression in those cells could achieve a better therapeutic outcome.


While numerous studies have provided evidence for selection history as a robust influence on attentional allocation, it is unclear precisely which behavioral factors can result in this form of attentional bias. In the current study, we focus on “learned prioritization” as an underlying mechanism of selection history and its effects on selective attention. We conducted two experiments, each starting with a training phase to ensure that participants learned different stimulus priorities. This was accomplished via a visual search task in which a specific color was consistently more relevant when presented together with another given color. In Experiment 1, one color was always prioritized over another color and inferior to a third color, such that each color had an equal overall priority by the end of the training session. In Experiment 2, the three different colors had unequal priorities at the end of the training session. A subsequent testing phase in which participants had to search for a shape-defined target showed that only stimuli with unequal overall priorities (Experiment 2) affected attentional selection, with increased reaction times when a distractor was presented in a previously high-priority compared with a low-priority color. These results demonstrate that adopting an attentional set where certain stimuli are prioritized over others can result in a lingering attentional bias and further suggest that selection history does not equally operate on all previously selected stimuli. Finally, we propose that findings in value-driven attention studies where high-value and low-value signaling stimuli differentially capture attention may be a result of learned prioritization rather than reward. Evidence is rapidly accumulating that a stimulus’s history can result in a lingering attentional bias toward that stimulus or its features  will almost always have a higher priority than selecting a nonthreatening stimulus . The present study further investigates whether the observed high-reward versus low-reward bias on attention can be explained in terms of prioritization rather than being a direct effect of the availability of reward. To this end, the current study aims to investigate whether adopting a top-down set that unequally prioritizes different stimuli can lead to effects of selection history that mirror the effects obtained by high-reward and low-reward signaling stimuli in value-driven capture tasks. Such an observation would provide evidence that attentional modulation due to selection history can be achieved in the absence of reward, but that reward can potentially modulate the behavioral priority of different stimuli. An explanation in terms of “prioritization” could be instrumental in understanding the discrepant findings concerning the necessity of value in selection history.We conducted two experiments to address the aforementioned questions by manipulating the priority of differently colored stimuli in a training/testing paradigm typically used in studies of value-driven attention  were presented in a circular array consisting of otherwise gray shapes. At the start of the training phase, on-screen instructions were shown explaining which colored circle in each of three possible color pairs contained the target stimulus. The initial training phase was used to further consolidate the learned schemes by having participants repeatedly select the prioritized colored circle and to respond to the target presented inside that stimulus. As illustrated in the left panel of Fig. SD = 4.83 years). All participants gave written, informed consent prior to the experiment. All protocols and procedures were approved by the Vrije Universiteit Amsterdam Ethical Committee, in line with the Declaration of Helsinki.We tested 35 participants with normal or corrected-to-normal vision and no reported history of mental illness. The data of three participants were discarded, as their average accuracy scores on either the training or testing task were more than 2.5 standard deviation below the group mean. Of the 32 remaining participants, 22 were female, and participants had an average age of 21.84 years . Prior to the start of both tasks, instructions were presented on-screen, and the experimenter verified that participants fully understood the task. Both tasks were conducted in a dimly lit, sound-attenuated room on a standard PC with a 22-in. monitor. Viewing distance was fixed at 75 cm. MATLAB® 2016a and Psychtoolbox 3  and two shapes that were presented in different colors . Every shape in the search display contained a gray “T” (11.4 cd/m2) that could be rotated 0°, 90°, 180°, or 270°. The target was defined as the “T” shape presented inside one of the two colored shapes, depending on the particular priority schemes the participant was shown at the start of the experiment (described in a subsequent paragraph). All stimuli were presented on a black background. Participants were instructed to respond as quickly and accurately as possible to the orientation of the target “T” using the four arrow keys on the computer keyboard . Note that the orientation of all “T”s in the display were randomly chosen with the exception that the “T”s in the two colored shapes were always differently oriented, such that selecting the wrong color for the particular priority scheme always resulted in an incorrect response. After participants responded, accuracy feedback was presented in the center of the screen (“correct”/“incorrect”) for 500 ms. Erroneous responses as well as timed-out trials were considered incorrect in this and all further experiments.The left panel of Fig. At the start of the experiment, participants were presented with three color-response schemes see Fig.  and wereThe training phase consisted of eight blocks of 72 trials each , preceded by two practice blocks of 48 trials each. After each trial in the first practice block, participants received feedback about their accuracy and were presented with an illustration of the color-response scheme defining the target for that trial. Pressing the space bar would start the next trial. In the second practice block, participants again received accuracy feedback after each trial, but the color-response scheme was only presented when the participants responded incorrectly.The testing task  = 1.687, p = .194, ηp2 = .052 (see Table t test), t(31) = 38.91, p < .001, confirming that participants had adequately learned the priority schemes.We began our analysis by confirming that priority averaged out over the course of the training task, such that there were no overall differences in response times between the three different priority schemes. We only analyzed nonpractice trials with correct responses . Furthermore, we normalized the response-time data by trimming trials with correct response times that were 2.5 standard deviations above the conditional mean response time , or trials in which the response was faster than 200 ms . All further reaction time analyses are based on the mean response times obtained for each participant and condition. A repeated-measures ANOVA on the mean response times, with color scheme  as the only within-subjects factor, did not yield any significant effects (F < 1) or shape priority (F < 1), nor an interaction between these factors .As every trial in the testing task included two colors from the training task, we compared performance in trials with the target shape presented in a prioritized color to performance in trials with the distractor shape presented in the prioritized color. Practice and erroneous trials  were excluded from the response-time analyses and the resultant data were also trimmed to normality by removing trials with response times that were 2.5 standard deviations above the conditional mean or faster than 200 ms . A repeated-measures ANOVA on the mean response times, with color scheme  and shape priority  as within-subject factors revealed neither evidence of effects of color scheme  = 1.169, p = .318, ηp2 = .036. Again, no differences between target and distractor priority were present for any of the color schemes . Table The same patterns of null effects were observed when the ANOVA was carried out on the accuracy data, shape priority: The results of Experiment 1 provided no evidence that differentially prioritized stimuli have differing effects on attentional capture when presented simultaneously. No differences in response times were observed between trials with the target versus distractor shape presented in a prioritized color. Importantly, priority was only established at the trial level in Experiment 1 and averaged out over the three possible colors throughout the course of the training task. Although these patterns of null effects are not conclusive, they suggest that this sort of situational prioritization at the trial level may not elicit differential effects of selection history. We tested prioritization at the trial level, but not the task level, as a proxy for situational priority relationships in the real world where a given stimulus or feature may be prioritized in one situation but deprioritized in another situation. Although Experiment 1 did not uncover any evidence that this sort of situational prioritization takes places at the task level, we tested the possibility that stimuli with fixed priority relationships throughout the course of both training and testing tasks may elicit effects of selection history in Experiment 2.and the task level .We tested 30 participants with normal or corrected-to-normal vision and no history of mental illness. Two participants (not included in these demographics) were replaced due to technical difficulties during experimentation. Of the remaining 28 participants, 21 were female, with an overall participant age of 21.54 years , meaning color was no longer prioritized by target selection. However, in Experiment 2, only one colored stimulus was present in the testing display on a random 50% of trials , and two colored stimuli were present on the other 50% of testing trials. When only one colored stimulus was presented, it was never the singleton shape target and instead functioned as a pop-out distractor. When two colored stimuli were presented, one was always the target singleton shape, and the other was the salient distractor shape. We included trials with only one color to measure the extent to which attention was captured by colored stimuli with different priorities, independent of the learned color-response contingencies between pairs of colors. We used the trials with two colors to compare how stimuli with fixed priority relationships compete for attentional resources. Every color pair was presented equally often, such that the target was presented in a higher priority color (HPC or LPC) than the distractor (LPC or NPC) on a random 50% of these two-color trials in the testing task and the distractor was presented in the higher priority color compared to the target in the remaining half of testing trials. The testing phase consisted of four blocks of 96 trials , preceded by a single practice block of 30 trials.F = 23.004, p < .001, ηp2 = .460, such that follow-up planned comparisons confirmed that correct response times for Scheme B trials were significantly faster (641 ms) than response times for Scheme A trials  and Scheme C trials , but that response times for Scheme A and Scheme C trials were not significantly different (p = .589). Overall accuracy scores were relatively high (94.70% correct) and well above 25% chance performance, t(27) = 131.833, p < .001. A second repeated-measures ANOVA on the accuracy data also revealed a main effect of scheme on accuracy , F = 20.077, p < .001, ηp2 = .426. Follow-up planned t tests explicated that mean accuracy for trials in each of the three schemes differed significantly, with the most accurate performance occurring for Scheme B . See Table To determine whether the three different priority schemes affected response times in the training task, we first conducted a repeated-measures ANOVA on participants’ nonpractice, correct , 2.5-standard-deviation-normalized response times . There was a main effect of scheme, After confirming that fixed priorities were successfully associated with the three colors in the training task, we next analyzed the testing task data to determine whether the color priorities instilled at the trial and task levels in the training task would carry over to capture attention in the testing task. As in all previous analyses, we only analyzed nonpractice trial correct responses  within 2.5 standard deviations above the participant’s conditional mean . We then conducted separate analyses on response time and accuracy data for trials with only one color  = 3.233, p = .047, ηp2 = .107 . Surprisingly, the difference between high priority and no priority color failed to reach significance (p = .17). There was no significant difference in response times between trials with low and no priority color distractors (p = .26). Accuracy results were in line with the reaction time observations, as indicated by a main effect of priority , F = 5.254, p = .008, ηp2 = .163  or no-priority distractor (p = .018). No difference was observed between trials with a low versus no-priority distractor (p = .96).A repeated-measures ANOVA on participants’ averaged response times for one priority color (distractor) trials revealed a significant main effect of this color , F = 29.102, p < .001, ηp2 = .519, such that participants responded faster to trials in which target was prioritized over the distractor (827 ms) compared with response times for trials in which the distractor was prioritized over the target  = 1.520, p = .228, ηp2 = .053, nor a significant interaction, F = 1.314, p = .277, ηp2 = .046, we nevertheless conducted planned comparisons between the three schemes to quantify any lingering effects of differential prioritization. These comparisons revealed significantly faster correct response times for trials with targets versus distractors presented in the prioritized color for each of the three scheme , suggesting that imbalances in prioritization carry over as lingering effects of selection history.To investigate whether color prioritization in the training task carried over in the form of lingering attentional bias in the testing task, we next conducted a repeated-measures ANOVA, with shape priority  and scheme  on participants’ averaged response times in the two-color trials. Importantly, each display in the two-color trials always consisted of one shape presented in a color that previously had a higher priority than the color of the other shape. On half the trials, the target shape singleton was presented in the higher priority color and the distractor in the lower priority color, and vice versa on the remaining trials. The ANOVA resulted in a main effect of shape priority, F, 54 = 29F = 7.438, p = .011, ηp2 = .216. No significant effect of scheme was observed, F = 1.739, p = .185, ηp2 = .061, nor did the interaction between scheme and shape priority reach significance, F = 2.520, p = .090, ηp2 = .085  and scheme , revealed a main effect of shape priority, indicating that participants responded more accurately when the target was prioritized over the distractor (85.0% correct) as compared with trials in which the distractor was prioritized over the target (81.9% correct), F1, 7 = 7.438Experiment 2 confirmed that effects of selection history can be observed when stimuli are prioritized in a fixed manner at both the task and trial levels. Effects of prioritization were already apparent in the training task, where participants responded faster and more accurately for Scheme B trials compared with Scheme A or C trials. Although these results could potentially be caused by selection history effects, they are at least equally likely caused by differences in ambiguity concerning which stimulus a participant has to respond to. In Scheme B, there is the least ambiguity about which stimulus contains the target because the target was always presented in the high-priority color  and the distractor was always presented in the no-priority color (the color that never required a response). Given that high overall accuracy in the training task suggested the color schemes were all well learned (like in Experiment 1), we instead turned to the testing data to further quantify the effects of fixed prioritization. The testing phase data showed clear lingering effects due to selection history, such that a stimulus with a higher versus lower priority had more influence on attentional allocation. This pattern was observed for all paired levels of prioritization . Therefore, the results of Experiment 2 suggest that fixed prioritization influences attention even when the prioritized feature is no longer task relevant.F = 20.227, p < .001, ηp2 = .259. As expected, there was a significant interaction between shape priority and experiment, F = 15.158, p = .001, ηp2 = .207. Follow-up planned comparisons showed no significant difference between target and distractor prioritization in Experiment 1 , but a significant difference between target and distractor priority in Experiment 2 , confirming that the main effect of shape priority was driven by the fixed priority relationships established in Experiment 2. A similar interaction between shape priority and experiment was observed for the accuracy scores, indicating that the difference between target and distractor priority in Experiment 2 , was larger than the same effect in Experiment 1 . These results once more confirm that situational priority does not lead to observable differences in terms of selection history, whereas fixed priority does.We also conducted a cross-experiment mixed-design ANOVA, with shape priority as a within-subjects factor and experiment as a between-subjects factor on the averaged response-time data for trials in both experiments with two colored stimuli, to assess potential differences between selection effects due to situational (Experiment 1) versus fixed (Experiment 2) prioritization. We observed a main effect of shape priority, such that participants made faster correct responses when the shape singleton target was presented in the higher priority color (887 ms) compared with correct response times for trials with the distractor presented in the higher priority color (908 ms), We investigated whether stimuli prioritized during an initial training task would lead to attentional biases due to selection history in a subsequent testing task where priority was no longer enforced or task relevant. Indeed, results suggest that previously prioritized stimuli can lead to attentional capture. However, whether capture occurs depends on the nature of the priority relationships. Significant effects of attentional capture by previously prioritized stimuli were observed only in Experiment 2, when the prioritized stimuli shared a fixed priority relationship such that throughout the experiment, different colors had a ranked priority that never changed. Experiment 2 showed that under such fixed circumstances, when a single colored stimulus was presented as one of the distractors in the testing task, attentional capture was observed such that correct response times were slower and accuracy decreased when the distractor was presented in the HPC compared with when it was presented in the LPC. When both the target and distractor were presented in prioritized colors, response times were biased by the higher priority stimulus such that participants were faster when the target versus distractor was presented in the higher priority color. On the contrary, when stimuli were only situationally prioritized at the trial level in Experiment 1, there were no corresponding effects of capture during the testing phase. Furthermore, the significant interaction between shape priority and experiment in the cross-experiment analysis offered further support for the proposal that fixed, but not situational, priority induced lingering effects of selection history.The present findings add to our understanding of the attentional phenomenon of selection history. A number of attentional effects have been retroactively linked to selection history, such as intertrial priming , which led to the exclusion of three participants in Experiment 1. Alternatively, we could have chosen to use a less strict criterion and exclude only those participants that scored below chance level. Using a chance-level criterion would not have led to the exclusion of the three participants in Experiment 1. Nonetheless, a recalculation of all statistical tests that included the data of the three discarded participants did not change any result and conclusion drawn here.Finally, throughout the current study, theoretical comparisons between learned prioritization and value-driven attentional capture have been put forward. The current study provides support for recent studies that have shown that the administration of reward is not a necessity for observing lingering effects of stimulus history on attentional selection (Grubb & Li, Grubb and Li  further


Clopidogrel is increasingly being used for the secondary prevention of ischemic stroke according to the updated guidelines on acute stroke management. Failure to achieve a drug response is referred to as clopidogrel resistance. Similarly, a higher activation of platelets during clopidogrel therapy—high on-treatment platelet reactivity—is equivalent to a reduced effectiveness of a therapy. Clopidogrel resistance is considered to be a common and multifactorial phenomenon that significantly limits the efficacy of antiplatelet agents. The aim of the current study is to review the latest literature data to identify the prevalance and predictors of clopidogrel high on-treatment platelet reactivity among stroke subjects and to establish the potential impact on clinical outcomes and prognosis. Clinical databases were searched by two independent researchers to select relevant papers on the topic, including all types of articles. Several important predictors contributing to clopidogrel resistance were identified, including genetic polymorphisms, the concomitant use of other drugs, or vascular risk factors, in particular nonsmoking and diabetes. Clopidogrel high on-treatment platelet reactivity has a negative impact on the clinical course of stroke, worsens the early- and long-term prognoses, and increases the risk of recurrent vascular events. Platelet function testing should be considered in selected stroke individuals, especially those predisposed to clopidogrel resistance, for whom an improvement in the efficacy of antiplatelet therapy is essential. This particular group may become the greatest beneficiaries of the modification of existing therapy based on platelet function monitoring. Clopidogrel is one of the most widely used antiplatelet agents worldwide. It has an established position as an antagonist of platelet function, leading to a reduced risk of recurrent ischemic events. It plays a primary role in the prevention of coronary heart disease in the field of cardiology. Due to the updated guidelines on stroke, this drug is also increasingly being used for the secondary prevention of ischemic stroke . It mighUnfortunately, knowledge of the role of clopidogrel resistance in ischemic stroke is not well established. In contrast, there are numerous reports on coronary heart disease that encourage individual or personalized treatments based on platelet function testing ,7. ThereABCB1 gene [CYP2C19) (responsible for approximately 50% of active metabolites) and the cytochrome P450 3A4 gene (CYP3A4) (39.8% of active metabolites) [P2RY12 gene encodes the P2Y12 receptor and GPIIIa gene–GPIIb/IIIa complex, a biologic activity target and effector of clopidogrel [Clopidogrel is a pro-drug and is inactive in vitro. It must be biotransformed in the human body after oral ingestion to become operational. Antiaggregative properties are produced by an active shortlisting metabolite generated by the cytochrome P450 (CYP)-dependent pathway in the liver. This is contradictory to other antiplatelet agents, such as aspirin or ticagrerol, which are active from the beginning and do not need to undergo transformation. The inhibition of platelets is a result of the irreversible binding of P2Y12 receptors. Adenosine diphosphate (ADP) activates platelets by binding the two protein receptors on the platelets (P2Y1 and P2Y12), leading to ADP-mediated platelet aggregation with the glycoprotein IIb/IIIa (GPIIb/IIIa) complex pathway. As an ADP receptor inhibitor, clopidogrel prevents platelet aggregation, but it does not interfere with arachidonic acid metabolic pathways . There abolites) . The P2Rpidogrel . Geneticpidogrel .There are several platelet function assays that can be performed to assess the platelet reactivity. The most commonly used are turbidimetric aggerogometry , moderately high shear stress platelet function analysis , light transmission aggregometry , vasodilator-stimulated phosphoprotein phosphorylation assay , and impedance aggregometry . Most platelet function assays measure the level of platelet aggregation in response to a variety of agonists. A higher activation of platelets during clopidogrel therapy high on-treatment platelet reactivity is equivalent to a reduced effectiveness of a therapy. Different assays use specific cut-off points to identify clopidorel resistance or high on-treatment platelet reactivity, e.g., VerifyNow has more than 230 P2Y12 reactive units (PRU); Multiplate has more than 47 Units, PFA-100 has less than 106 s of closure time; LTA has an aggregation rate of >70% or >46%; VASP has a platelet reactivity index of greater than 50% ,17. SomeThe prevalence of clopidogrel resistance in ischemic stroke patients is variable and depends mainly on the method used for the assessment of platelet reactivity and the cut-off value used. In ischemic stroke research, the most frequently used technique to measure platelet aggregation is LTA. Prevalence rates fall into fairly wide ranges (16.83% to 50%) ,18,21. IThe response to the drug may be influenced by genetics or by clinical and pathophysiological factors .CYP2C19 polymorphisms. Recent studies have demonstrated that carriers with one or more CYP2C19 loss-of-function alleles (2* or 3*) are at a higher risk of clopidogrel nonresponsiveness due to having lower levels of its active metabolite [CYP2C19 loss-of-function allele, the percentage of individuals with clopidogrel resistance is estimated to be 71.7% which is significantly different from the prevalence of this phenomenon in noncarriers—32.1% [CYP2C19 2* or 3* carriers compared with noncarriers , and Liu et al. [CYP2C19*2 allele carriers is higher than that of noncarriers (odds ratio (OR) = 2.366; p = 0.014). However, it is worth emphasizing that carriers of CYP2C19 loss-of-function alleles were found to be significantly more likely to have clopidogrel high on-treatment platelet reactivity, but not an increased risk or higher recurrence of vascular events [CYP3A4. The CYP3A4*1G variant is considered to be a protective factor in clopidogrel resistance among ischemic stroke patients. It is estimated that the most frequent mutant allele is associated with greater liver metabolic activity, leading to a higher concentration of active clopidogrel-related substances, thus increasing platelet inhibition. Liu demonstrated that among CYP3A4*1G carriers, the estimated risk of clopidogrel resistance is significantly lower compared with that of noncarriers  [ABCB1 gene TT variant and the wild-type CC genotype have been associated with a higher risk of recurrent vascular events during clopidogrel treatment, but these findings were reported among coronary heart disease subjects [ABCB1 gene in ischemic stroke subjects. However, the above studies were limited by a single locus assessment and small sample sizes. Polymorphisms of the P2RY12 and GPIIIa genes have been shown to be associated with clopidogrel-dependent platelet reactivity [P2RY12 TT+CT carriers are more likely to have a higher platelet reactivity following a clopidogrel treatment than P2RY12 CC carriers, and Liu et al. [P2RY12 H2 haplotype compared with those with the H1 haplotype, but this result did not reach statistical significance. Yi et al. [GPIIIa AA carriers and AG+GG carriers differed significantly in terms of the incidence of platelet activity on clopidogrel therapy (p = 0.042). It has been noted that interactions between genes may have a greater impact on platelet activity than the effect of a single gene polymorphism. Moreover, it has been underlined that clopidogrel resistance may not be attributed to single genetic variants at individual loci alone but may be conditioned by multiple gene–gene intracations. Yi et al. [CYP2C19, P2RY12, and GPIIIa variants are independently associated with the efficacy of clopidogrel. Furthermore, the synergistic effect of genes interactions may contribute not only to platelet activity but also to stroke prognosis. Yi et al. [p = 0.003). The molecular mechanisms responsible for the above characteristics still remain unclear.As mentioned above, many different genes are involved in the biotransformation of clopidogrel into the active substance. Their polymorphisms may interfere with the above process, leading to a lower amount of active metabolites, resulting in a reduced drug efficacy. The most common gene variant described in the literature related to clopidogrel resistance concerns tabolite . It is etabolite . Fu et ars—32.1% . Similarrs—32.1%  demonstrr events ,29,30,31subjects . In contsubjects  and Yi eactivity ,35,36. Au et al.  reportedCYP3A4 complex, while others, such as pravastatin or fluvastatin, do not. The related data on coronary heart disease are controversial. Some studies have not reported a negative interaction of statin coadministration (regardless of the pathway of biotransformation) with clopidogrel effectiveness in subjects undergoing coronary stenting [p = 0.25). To the best of our knowledge, there is currently no study indicating a significant negative impact of statin coadministration on the inhibitory effect of clopidogrel on platelet function in ischemic stroke patients.Most drugs are metabolized in the liver via similar enzyme pathways to the one that produces clopidogrel. Thus, the coadministration of several drugs may competitively reduce the effectiveness of each of them. The most commonly used concomitant drugs in the secondary prevention of stroke are the 3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors (statins) and proton pump inhibitors, a protocol that is used to reduce the risk of developing gastrointestinal complications from antiplatelet agents. Most statins, including atorvastatin, lovastatin, or simvastatin, are extensively metabolized by the stenting . In contstenting  demonstrstenting ,14,21,40stenting  reportedCYP2C19, the coadministration of omeprazole or esomeprazole may be associated with a reduced efficacy of platelet inhibition by clopidogrel [p = 0.02), but these factors were not significantly correlated in a mutlivariate analysis (p = 0.10). Yi et al. [p = 0.71). In contrast, Su et al. [p < 0.001). Overall, based on the above inconsistent findings, proton pump inhibitors that are not involved in the CYP2C19 pathway, such as pantoprazole, ranitidine, or famotidine, should be administered, if clinically warranted, in combination with clopidogrel to avoid competition in terms of the mechanism of action and to provide effective antiplatelet therapy [Data on drug–drug interactions involving proton pump inhibitors and clopidogrel seem to be more conflicting. Several studies have shown that, due to the potent inhibition of pidogrel . Moreovepidogrel . Data onpidogrel  demonstri et al.  noted thu et al.  demonstr therapy .Many reports in the literature refer to the relationships of established risk factors for the development of vascular diseases, including stroke, with the antiplatelet effect of clopidogrel. Several studies have revealed that, in ischemic stroke subjects, clopidogrel high on-treatment platelet reactivity is significantly associated with diabetes ,14,22,40p = 0.002) than nonsmokers and, additionally, the incidence of clopidogrel resistance is significantly lower in smokers . Zhang et al. [Many interesting insights have resulted from studies on the influence of smoking on platelet reactivity during clopidogrel therapy. Many researchers have described the smokers’ paradox, which is that smokers experience better antiplatelet effects following clopidogrel treatment than nonsmokers, resulting in stronger platelet inhibition, in particular, in patients with coronary heart disease . Kang etg et al.  concludeg et al. . The expg et al. . Other rJeon showed that clopidogrel resistance in ischemic stroke patients is significantly asssociated with a higher white blood count and C-reactive protein (CRP) level . SimilarPrevious studies have shown that aspirin resistance may be associated with a large vessel disease background in ischemic stroke patients . Reportsp < 0.001). In particular, recurrent ischemic stroke was more strongly associated with the clopidogrel-resistant subgroup than the clopidogrel responders . However, the incidence of myocardial infarction and death due to vascular causes did not differ significantly between the above groups. Furthermore, in a multivariate regression analysis, the clopidogrel high on-treatment platelet reactivity was found to be the most significant independent risk factor for recurrent ischemic events . In another study, also with a 6 month follow up period, in clopidogrel resistant subjects, a significant association with adverse clinical outcomes in all patients (p = 0.023) and in those with recurrent ischemic stroke (p = 0.021) was demonstrated, compared with clopidogrel responders [p = 0.83) or sudden death of vascular origin (p = 0.82), but it was shown to be an independent predictor of adverse events . A survival analysis by Fu et al. [p = 0.04). Furthermore, clopidogrel high on-treatment platelet reactivity was considered an independent predictor of recurrent clinical events . However, data on individual vascular events are lacking. Rao et al. [p = 0.784, myocardial infarction p = 0.223; vascular death p = 0.752) between clopidogrel-resistant and sensitive subgroups [The main goal of antiplatelet therapy as part of secondary prevention is to decrease the risk of recurrent ischemic events after the onset of ischemic stroke. The most common event is another recurrent stroke or transient ischemic attack, but stroke subjects are also at a higher risk of myocardial infarction (MI), sudden cardiac death, acute limb ischemia, or systemic embolism. Previous studies regarding aspirin resistance have demonstrated a significant, independent association between high on-treatment platelet reactivity and a higher risk of recurrent vascular events in stroke subjects . The datsponders . Similaru et al.  conducteo et al.  only fole p = 0.0 was demop = 0.029). However, only patients with large vessel disease as a cause of stroke were included in this study. Yi et al. [p = 0.001). At the same time, there was no significant difference in the clinical condition assessed with the NIHSS on the day of enrollment (acute phase of stroke) between clopidogrel responders and nonresponders . Conversely, Jeon [p = 0.015). Qiu et al. [p = 0.001). Yi et al. [p < 0.001). Subjects with clinical deterioration had significantly higher levels of platelet aggregation than patients without deterioration (p < 0.001). A regression analysis showed that clopidogrel resistance was an independent predictor of early neurological deterioration . These data underscore the significant influence of adequate platelet inhibition by clopidogrel on the clinical course of stroke and both early and late prognoses.Another very important issue related to the effective action of an antiplatelet agent is the reduction in the severity of ischemic stroke and the improvement of the prognosis and recovery. Therefore, it seems that clopidogrel resistance may significantly worsen the clinical and functional condition of stroke subjects and contribute to a poor prognosis and clinical outcome. Lee et al.  demonstri et al.  investigly, Jeon  showed tu et al.  indicatei et al.  investigp = 0.484). Similarly, Yi et al. [p = 0.992; p = 0.753). In another study, regarding late complications, Yi et al. [p = 0.95) and intracranial hemorrhage (p = 0.92). The above results suggest that the sensitivity of platelets to clopidogrel is not a risk factor for either early or late intracranial bleeding.Intracranial hemorhage, such as gastrointestinal or urinary bleeding, may be one of the adverse effects of antiplatelet therapy that could worsen the clinical condition and recovery. Some researchers have investigated whether the degree of platelet inhibition could contribute to symptomatic bleeding. Lee et al.  showed ti et al.  reportedi et al.  followedp = 0.01), while not increasing the risk of sudden death or bleeding. Unfortunately, both studies included subjects based only on high on-treatment platelet reactivity, without differentiating them by additional determining factors which, in view of the above considerations, constitutes a limitation. Additionally, it should be emphasized that, compared to coronary artery disease, the capacity to modify antiplatelet treatment in stroke is significantly limited, as current guidelines recommend, apart from clopidogrel, only aspirin or dipyridamole.Due to the lack of support by large, randomized, multicenter, clinical trials, the assessment of platelet reactivity in ischemic stroke patients is not currently recommended for routine use. However, numerous significant relationships concerning multiple effects on the course of stroke suggest that, in some clinical situations, the determination of the degree of platelet inhibition may be useful for modifying or intensifying the efficacy of treatment. Based on the provided data, this group should especially include subjects with recurrent ischemic stroke or other vascular events, nonsmokers with long-term and advanced diabetes, and carriers of genetic variants promoting clopidogrel resistance, if available. Platelet function monitoring and confirmation of high platelet activity should be a sufficient reason to switch the antiplatetet agent to improve the effectiveness of secondary prevention treatment. Reports on therapy modification based on platelet function testing are negligible and inconclusive. In a retrospective study, Depta et al.  showed tThis comprehensive review included papers regarding connections between clopidogrel and platelet reactivity, in particular, among ischemic stroke subjects. Clinical databases were searched by two independent researchers. English studies of all types, especially clinical trials, orginal research, observational, cross-sectional and cohort studies, and reviews were included. The various stages of proper selection of data from the literature are presented in In summary, clopidogrel resistance in ischemic stroke patients was presented as a common and important phenomenon with a multifactorial background. Similar to aspirin resistance, it has a negative impact on the clinical course of stroke, worsens the early- and long-term prognoses and increases the risk of recurrent vascular events. This highlights the importance of effective antiplatelet therapy in preventing the occurrence of stroke and the growing role of platelet function monitoring to identify nonresponders and support personalized and improved treatments. Specific features of ischemic stroke patients who are particularly at risk of developing clopidogrel resistance have been identified, and these should be considered and used as indicators of platelet reactivity testing to ensure the maximum efficacy of antiplatelet therapy.


The p38 MAPK pathway is well known for its role in transducing stress signals from the environment. Many key players and regulatory mechanisms of this signaling cascade have been described to some extent. Nevertheless, p38 participates in a broad range of cellular activities, for many of which detailed molecular pictures are still lacking. Originally described as a tumor-suppressor kinase for its inhibitory role in RAS-dependent transformation, p38 can also function as a tumor promoter, as demonstrated by extensive experimental data. This finding has prompted the development of specific inhibitors that have been used in clinical trials to treat several human malignancies, although without much success to date. However, elucidating critical aspects of p38 biology, such as isoform-specific functions or its apparent dual nature during tumorigenesis, might open up new possibilities for therapy with unexpected potential. In this review, we provide an extensive description of the main biological functions of p38 and focus on recent studies that have addressed its role in cancer. Furthermore, we provide an updated overview of therapeutic strategies targeting p38 in cancer and promising alternatives currently being explored. Mitogen-activated protein kinase (MAPK) cascades are signaling components that show a high degree of conservation throughout evolution and play a key role in converting extracellular stimuli into a broad range of cellular responses. All MAPK signaling cascades consists of a three-tiered module of protein kinases: MAPK kinase kinases  at the top, MAPK kinases  in the middle, and MAPKs at the bottom .In mammals, three major MAPK cascades have been described. The ERK1/2 pathway is activated mainly by mitogens and has been shown to be upregulated in many human tumors. In contrast, the Jun N-terminal kinase (JNK) and p38 pathways are activated mostly by environmental and genotoxic stresses and are therefore, also generically known as stress-activated protein kinases or SAPKs. The JNK and p38 signaling pathways show a certain degree of redundancy in their actions; however, the extent of crosstalk between them and their implications in cell physiology regulation depends on the cellular type, tissue, and organism. This review outlines current understanding of p38 MAPK family members and their involvement in tumor development, as well as the strategies to treat cancer based on targeting p38.The four p38 MAPKs are encoded by distinct genes: p38α MAPK14), which comprises two different spliced variants; p38β (MAPK11); p38γ MAPK12); and p38δ (MAPK13) [; and p38, which cSeveral mouse models genetically targeting p38 have been produced. Of note, p38β, p38γ and p38δ knockout mice do not have developmental defects. Moreover, of these three models, only p38δ knockout mice display a clear phenotype. In this regard, these animals are protected against high-fat diet-induced insulin resistance through the regulation of PDK1 activity and insulin secretion. This observation, therefore, indicates that this MAPK isoform plays a key role in the regulation of glucose homeostasis ,8. MoreoFull activation of most protein kinases requires phosphorylation on a flexible motif known as the activation loop. In particular, p38 activation takes place by the dual phosphorylation of Thr and Tyr on the Thr‒Gly‒Tyr motif located on the activation loop found on the kinase subdomain VIII . Dual phThe p38α isoform can be activated by noncanonical mechanisms see . One of The strength and dynamics of p38 pathway signaling are key elements in determining proper cellular responses . MoreoveTo date, a full characterization of the p38 phosphoproteome has not been performed . All p38Upon phosphorylation-mediated activation, p38 can in turn phosphorylate both cytoplasmic and nuclear proteins. In order to have access to nuclear substrates, activated p38 transiently accumulates and translocates to the cell nucleus. Since MAPKs do not have nuclear localization or nuclear export motifs, the molecular mechanism by which translocate into the nucleus is not fully known. Given that p38α can genetically complement a budding yeast strain lacking the p38-homologous Hog1 MAPK , initialFinally, p38 signaling ends upon the removal of the phosphates from the Thr‒Gly‒Tyr motif. Several Ser/Thr phosphatases, such as PP2A and PP2C, have been described to remove the threonine phosphate on the activation motif. The action of these phosphatases leads to the appearance of Tyr monophosphorylated p38 forms that lack kinase activity . In addip38 is activated by a wide range of environmental stimuli , genotoxic and DNA damaging agents , inflammatory cytokines, PAMPs (pathogen-associated molecular patterns), and DAMPs (danger-associated molecular patterns) .p38 is a multitasking kinase that regulates multiple cellular functions, including cell proliferation, differentiation, stress response, apoptosis, and cell migration and survival, among others, by interacting with a plethora of substrates . Part ofThe contributions to physiology of p38 have been addressed, mostly by using inhibitors that block kinase activation, as well as by using genetically engineered mouse models. Since mice lacking p38α die before birth, some of the strategies to overcome this include the generation of p38α tissue-specific conditional knockouts, deletion of upstream or downstream proteins of the MAPK pathway like MKK3/6, MSK1/2, MK2, or WHIP1, and generation of dominant negative p38α forms .The ablation of p38α leads to an increased proliferation of hematopoietic progenitor cells through the regulation of Epo expression , as wellOf particular importance is the capacity of p38 to control cell cycle progression, which is crucial for cellular homeostasis. p38 regulates proliferation at both G1/S and G2/M phases of the cell cycle by activating checkpoint responses .Exposure to osmotic stress, reactive oxygen species, DNA damage, and prosenescence stimuli activates p38 signaling, thereby leading to the induction of the G1/S checkpoint. p38 activity promotes the downregulation of cyclin D1, which is essential for S phase transition. This downregulation is achieved by stimulating ubiquitin-dependent degradation of cyclin D1  and inhiNotably, and contrary to what is commonly reported, p38 can enhance proliferation. However, this effect has been observed only in hematopoietic cells and in some cancer cell lines . Such anThe role of p38 in cancer has been extensively studied. Several reports have shown that p38 functions as an antitumorigenic factor see . Its rolThe importance of the p38 pathway in the regulation of the immune response has attracted considerable attention in the context of carcinogenesis. Immune cells can strongly modulate tumor progression by secreting cytokines and chemokines. Indeed, cancer and inflammation are tightly associated, and some chronic inflammatory diseases, particularly those occurring in the gastrointestinal tract, correlate with a higher risk of cancer development . p38 regThe role of p38 in promoting cell differentiation has also been reported to be relevant for its tumor inhibitory activity. In rhabdomyosarcoma cells, expression of either MKK3 or MKK6 reactivates the pathway, leading to terminal differentiation of cancer cells . DeletioAdditionally, the pro-apoptotic activity of p38 is related to its ability to inhibit tumor growth. This is particularly evident in cases where the effects of chemotherapeutic drugs rely on p38 activation . AnotherDespite numerous studies that provide experimental evidence of the antitumorigenic role of p38, many others demonstrate that this kinase promotes cancer by enhancing survival, migration, or resistance to stress and chemotherapeutic agents in tumor cells  see Fig. p38α waIn contrast to the p38α tumor-suppressing role, p38γ is required for Ras transformation in a phosphorylation-independent manner. In this regard, the expression of p38γ is selectively induced in colon cancer cells harboring mutated Ras and is required for proliferation ,97, therCompared to other genes that present recurrent mutations in several cancer types, the p38 gene does not show systematic loss-of-function mutations in common human malignancies. In total, results obtained from the sequencing analysis of a pool of 1500 samples revealed that the frequency of p38 mutations  in human cancers is lower than 1% . This inThe stage of tumor development could be a strong component governing the function of p38 in tumorigenesis. Cancer is a highly complex pathology in which genetic and metabolic rearrangements occur in every step. Therefore, tumor requirements are completely stage-dependent. In general, experimental evidence indicates that low p38 activity impairs tumor formation and growth during early stages of the disease, while more advanced tumor stages can benefit from higher activation of the pathway . An exteCancer is not simply a collection of cells that develop independently from their surroundings. The relevance of the tumor microenvironment as an active component of cancer development has gained special attention in recent years, although it is still a largely unexplored field. Extensive communication between cancerous and nontransformed cells takes place through a continuous flux of cytokines, chemokines, growth factors, and extracellular enzymes and determines tumor survival and progression . A recenTumor cells can detach from the initial tumor mass to migrate and invade other tissues, severely affecting homeostasis. This invasive process, known as metastasis, is by far the highest risk factor in cancer and is estimated to account for about 90% of deaths in cancer patients . There ip38 might also be involved in tumor metastasis via other mechanisms. For instance, p38 reduces the expression of the extracellular glycoprotein fibulin 3, which regulates cell migration . Indeed,As stated above, abundant experimental evidence shows that p38 can exert pro-oncogenic functions in various types of cancer. This finding opens up the possibility of developing cancer therapies based on small inhibitory compounds. Seven clinical trials targeting p38 for the treatment of cancer are currently underway see . One exaAlthough many efforts have been channeled into developing effective p38 inhibitors for clinical practice, almost all the trials performed to date in patients have failed, and no compounds have yet been approved. The appearance of systemic side effects in the heart, liver, and nervous system caused by such small molecule inhibitors accounts for the failure of many of these trials . These sA second approach to improve the effectiveness of cancer treatments involves targeting other kinases downstream the p38 pathway, thus limiting the response to only a subset of p38-mediated responses. For instance, the modulation of MAPKAPK2 (MK2), which is a direct downstream kinase of p38 that regulates several processes, including apoptosis, cell cycle, and stress response to oxidizing agents. MK2 regulates the expression of pro-inflammatory factors and responds to DNA damage by inducing the G2/M checkpoint response, thereby contributing to tumor growth and invasiveness in several cancer types ,118,119.S249E/T252E mutant acts as a super-repressor and blocks cyclin expression, preventing cell proliferation in all the cancer cell lines tested so far  and leading to reduced tumor formation in a mouse xenograft model of triple-negative breast cancer (TNBC) [The retinoblastoma (RB) protein emerges as another interesting potential candidate and a therapeutic target downstream of p38. RB is essential for the proper modulation of the G1/S cell cycle transition, and its inactivation contributes to deregulated cell proliferation, which is a hallmark of cancer, thus leading to tumorigenesis . As mentr (TNBC) ,73,83. Fr (TNBC) . In thisr (TNBC) , so patiDespite the limited success of medicinal chemistry to design a drug that targets p38 with a clear therapeutic effect, this stress-activated kinase or its downstream components remain an attractive candidate for the development of new therapies. Indeed, there is still very limited knowledge about some basic aspects of the functionality of the p38 pathway. For instance, p38 isoform-specific biological functions remain a mystery. Specifically, p38δ and p38γ, which have unique expression patterns and perform a different set of functions, have received less attention than p38α and p38β.p38 has classically been considered a tumor suppressor gene, in spite of the lack of mutations in the genomic sequence in human cancers. However, there is now a large collection of publications supporting a tumor promoter role for p38 and thus in disagreement with its former classification as a prominently anticancer protein. In particular, the role of p38 in metastasis is gathering attention exponentially, since advanced tumorigenic stages still represent a major health challenge worldwide. Nevertheless, even with the increasing body of evidence and studies available, a clear picture of the contribution of p38 to tumorigenesis is still missing. In this regard, many cancer-related studies lack an isoform-dependent approach and hence their translational potential is limited. In this regard, the way each p38 isoform, especially δ and γ, contributes to oncogenesis is not well understood and the results can often be controversial. Moreover, the large versatility of the stress-activated pathway is probably another important handicap to the effectiveness of therapies. It is evident that the factors mentioned above have hindered the development of more effective and safer drugs for specific malignancies.A deeper understanding of the p38 pathway will translate into better therapeutic strategies for the treatment of cancer, with overall higher success rates. Nevertheless, and considering what has been explained above, it should be taken into account that, while p38 inhibition-based therapies efficiently block tumor growth, they might simultaneously facilitate malignant initiation in other tissues subjected to oncogenic stimuli. As discussed in the previous section, other therapeutic options are also being explored intensively, with the aim of overcoming this hurdle. One particular alternative involves the combination of existing drugs with p38 small inhibitors, while another seeks to target upstream or downstream regulatory factors within the pathway. The rationale behind the latter is that a focus on other regulatory proteins might bypass the undesirable pleiotropic effects caused by p38 inhibition. In particular, recent studies have been devoted to MK2 kinase downstream of p38, and to RB, a p38-dependent transcriptional regulator of cell proliferation. Remarkably, experiments targeting these two proteins have shown promising results in vivo, thereby reflecting their exceptional potential for clinical applications.


The nuclear transcription factor p53, discovered in 1979, has a broad range of biological functions, primarily the regulation of apoptosis, the cell cycle, and DNA repair. In addition to these canonical functions, a growing body of evidence suggests that p53 plays an important role in regulating intracellular redox homeostasis through transcriptional and nontranscriptional mechanisms. Oxidative stress induction and p53 activation are common responses to chemical exposure and are suggested to play critical roles in chemical-induced toxicity. The activation of p53 can exert either prooxidant or antioxidant activity, depending on the context. In this review, we discuss the functional role of p53 in regulating chemical-induced oxidative stress, summarize the potential signaling pathways involved in p53's regulation of chemically mediated oxidative stress, and propose issues that should be addressed in future studies to improve understanding of the relationship between p53 and chemical-induced oxidative stress. A number of cellular systems have been identified to contribute to ROS generation, including plasma membrane, cytosol, peroxisomes, mitochondria, and endoplasmic reticulum. Mechanistically, ROS generation is mainly due to excessive stimulation of NAD(P)H oxidases or the oxidative energy metabolism in mitochondria [An imbalance in the oxidation reduction (redox) system in favor of oxidants is known to cause oxidative stress, a condition that is characterized by the overproduction of reactive oxygen species (ROS) and/or decreased antioxidative capacity , 2. Typichondria .Oxidative stress has been shown to contribute to many pathological conditions, such as cancer –6, cardiThe major transcriptional factors involved in redox regulation include Nrf2, Nrf1, p53, and FoxO , 28–30. Oxidative stress can be activated in response to certain chemicals and has been demonstrated to play a critical role in their toxicity , 35–38. Cisplatin is a first-line therapeutic drug for certain types of cancer; however, its nephrotoxicity is a major impediment to its clinical application . It has α could ameliorate triptolide-induced apoptosis by suppressing ROS accumulation in primary cardiomyocytes H9c2 cells [Similarly, in the case of doxorubicin (DOX), a topoisomerase II inhibitor widely used in chemotherapy due to its efficacy in combating a wide range of cancers, the induction of cardiotoxicity is a major safety issue, with oxidative stress the most probable mechanism for its cardiotoxic effect . Using wc2 cells .Colistin, also known as polymyxin E, could be the first choice in the treatment of infections caused by multidrug-resistant Gram-negative bacteria ; howeverIn addition to the side effects of therapeutic drugs, p53-mediated oxidative stress has also been noted in toxicant-induced toxicities. Patulin, a mycotoxin produced mainly by Aspergillus and Penicillium, is commonly found in moldy fruits and their derivative products , and it α (PFTα) significantly reduced the expression of oxidative markers and glycerol-induced renal tubular injury in rats. These findings indicate that p53-mediated oxidative stress can contribute to glycerol-induced kidney injury.Glycerol is a simple polyol compound often used in the food, medical, and pharmaceutical industries and in personal care preparations . Howeverα treatment, silibinin could not induce ROS generation in the p53-mutated human epithelial tumor A431 cell. These findings further verify the crucial role of p53 in silibinin-induced ROS generation [Silibinin is a major active constituent of silymarin, and many studies have reported on the involvement of ROS and p53 in silibinin-activated pathways –52. In Hneration .In contrast to the prooxidant characteristics of p53, its antioxidant activity has also been reported to occur in chemically induced oxidative stress, as summarized in α, knockdown of p53 expression with antisense oligonucleotide, and p53 knockout, leads to more severe liver injury by APAP. Conversely, the activation of p53 by its activator, nutlin-3a, resulted in ameliorated APAP-induced hepatotoxicity. These results clearly suggest that p53 plays a novel protective role in APAP-induced liver injury. Moreover, it was revealed that the protective effect of p53 on APAP-induced hepatotoxicity is attributed to its ability to inhibit the activation of JNK, a key mediator in APAP-induced oxidative stress [Acetaminophen (APAP) is one of the most commonly used analgesic drugs and is usually safe at the appropriate therapeutic doses. However, excessive doses can induce hepatotoxicity, and APAP overdose has become the leading cause of liver injury in the United States and most European countries , 54. Huoe stress , 37, (Hu1-Methyl-4-phenylpyridinium (ion) (MPP+) is a dopamine neurotoxin, which can induce parkinsonism . MPP+ isThe antioxidant function of p53 has also been found in the oxidative stress-related pathology of cardiovascular diseases. Oxidative stress induced by free fatty acids (FFA), for example, is considered to be a contributing factor to the metabolic syndrome-associated development of cardiovascular diseases. Exposure of FFA palmitate to human endothelial cells (ECs) caused the transcriptional inactivation of p53 via the inhibition of its acetylation, which, in turn, led to increased ROS generation and endothelial damage . These iGlucose, which is a simple sugar that provides the body with its primary source of energy, has been found to lead to p53 inactivation and ROS accumulation in human umbilical vein endothelial cells (HUVEC) and human aortic endothelial cells (HAEC). Wu et al.  concludep53 is also involved in oxidative stress induction caused by nitric oxide in vascular smooth muscle cells (VSMC). Popowich et al.  reportedRecent research has identified the activities of p53 in the regulation of ROS, along with the upstream and downstream regulators responsible for p53 antioxidant and prooxidant functions. Numerous studies have shown, for example, that p53 can exert prooxidant activity to promote oxidative damage through the regulation of its transcriptional targets, such as p53-inducible genes (PIGs), NCF2/p67phox, a cytosolic subunit of the NADPH oxidase enzyme complex , 62, p66P66shc, a splice variant of p52shc/p46shc, is a cytosolic adapter protein that transduces mitogenic signals from activated receptors to Ras . p66shc α downregulates p66shc expression in vivo, a finding which was consistent with the results obtained in the cell culture model.The role of p66shc in chemically induced p53-mediated oxidative stress was examined in a study by Yuan et al.  in whichIn 1997, Polyak et al.  used theIt has been shown that mycotoxin patulin induces p53-mediated oxidative stress in kidney cells . To inveThe GPXs are a group of selenocysteine-containing antioxidant enzymes , of whicThe mitogen-activated protein kinase (MAPK) cascades are evolutionary conserved intracellular signal transduction pathways. They are involved in the transmission of mitogenic signals from the cell surface to regulatory targets and also regulate multiple cellular processes, including proliferation, differentiation, and cell death –79. To dIt is well established in APAP-induced liver injury that APAP induces the rapid production of the reactive metabolite NAPQI, followed by the depletion of glutathione (GSH) and generation of ROS, consequently resulting in the activation of JNK , 84. TheAs a family of evolutionarily conserved proteins, Sestrins can suppress reactive oxygen species and provide cytoprotection against oxidative stress –87. ThreSestrins have been widely reported to link p53 with redox regulation , 65, 88.Glutaminase (GLS), which is the initial enzyme in glutamine metabolism, has two isoenzymes, namely, GLS1 and GLS2 . GLS2 de2O2 induces GLS2 mRNA significantly in HCT116 p53+/+ cells but not in p53−/− cells, thus revealing that H2O2 induces GLS2 mRNA levels in a p53-dependent manner. It has also been found that p53 can regulate GLS2 basal expression levels in HepG2 cells. Moreover, H2O2 accumulates more ROS in HCT116 p53−/− cells than in p53+/+ cells, while silencing GLS2 can also increase ROS accumulation in HCT116, H1299, and HTB-15 cells. These findings demonstrate that p53 regulates cellular antioxidant defense through the modulation of GLS2 expression.GLS2 has also been reported to act as a mediator of p53's role in energy metabolism and antioxidant defense , 91. TreAs has been described above, p53 has the ability to exert either prooxidant activity to mediate chemically induced apoptosis or antioxidant activity to protect cells from chemically induced cytotoxicity. Therefore, p53 is considered a reasonable target through which to suppress chemically induced oxidative stress and toxicity , 43, 60.As mentioned above, p53 is an important transcription factor, and it transcriptionally regulates multiple downstream targets that are involved in regulating various biological processes such as cell cycle, apoptosis, and DNA repair. Targeting p53 could offer protection against chemical-induced oxidative stress and toxicity, but meanwhile, it might affect physiological functions of p53 to produce certain side effects. To avoid these unwanted influences, the manipulation of p53 needs to be optimized so that the basal p53 activity can be maintained to enable its physiological functions unaffected. For example, p53 was activated by PAT, which induced ROS generation and cytotoxicity . TitratiOxidative stress can lie either upstream or downstream of p53 activation, which has been found capable of exerting either prooxidant activity to mediate chemically induced apoptosis or antioxidant activity to protect cells from chemically induced cytotoxicity. The determinants of this paradoxical role of p53 in the regulation of oxidative stress remain elusive. It is generally believed that, under physiological conditions and the conditions of mild stress, p53 exerts antioxidant activity to inhibit ROS generation and protect cells from oxidative DNA damage, while under conditions of severe stress, activated p53 enhances oxidative stress and promotes cell death. Nonetheless, this speculation cannot account for all stress cases. p53 is activated in APP-treated liver cells, for example, and APAP treatment has been found to cause severe oxidative stress followed by severe liver injury. However, activated p53 is reported to play an antioxidant role in this stressed condition, which suggests the involvement of additional factors in determining the prooxidant or antioxidant function of p53.Evaluation of the influence of the source or type of ROS on the pro- or antioxidative activity of p53Assessment of the role of levels of p53 activation in response to chemical exposure in its pro- or antioxidative functionDetermination of whether the cell type is a contributing factor for the controversial function of p53 in regulating oxidative stressInvestigation of the novel mechanisms underlying p53-regulated oxidative stress in response to chemical exposureFurther investigations into the activity of p53 should address the following issues:A better understanding of the factors prompting the activity of p53 as either prooxidant or antioxidant will further the development of this important cell tumor antigen as a precisely utilized target to manage the oxidative stress-mediated toxic responses to chemical exposure.


In addition, p63 plays a key role as a quality control factor in oocytes and p63 mutations can result either in compromised genetic quality control or premature cell death of all oocytes.The protein p63 belongs to the family of the p53 tumor suppressor. Mouse models have, however, shown that it is not a classical tumor suppressor but instead involved in developmental processes. Mutations in the The p63 gene encodes a master regulator of epidermal commitment, development, and differentiation. Heterozygous mutations in the DNA binding domain cause Ectrodactyly, Ectodermal Dysplasia, characterized by limb deformation, cleft lip/palate, and ectodermal dysplasia while mutations in in the C-terminal domain of the α-isoform cause Ankyloblepharon-Ectodermal defects-Cleft lip/palate (AEC) syndrome, a life-threatening disorder characterized by skin fragility, severe, long-lasting skin erosions, and cleft lip/palate. The molecular disease mechanisms of these syndromes have recently become elucidated and have enhanced our understanding of the role of p63 in epidermal development. Here we review the molecular cause and functional consequences of these p63-mutations for skin development and discuss the consequences of p63 mutations for female fertility. Failure to maintain cellular homeostasis is a common driver of diseases like cancer and neurodegeneration, and also plays a role in ageing, immunological, and metabolic disorders. Quality control systems are the first line of defense that detect potentially stressful or dangerous conditions and provide the information for the cell to initiate countermeasures. Similarly, proper response to environmental cues and stress controls correct cell fate decisions that are essential for development and homeostasis of tissues and organs. Depending on the type of stress, the cellular response can include, for example, activation of DNA repair, cell cycle arrest, expression of chaperones, inhibition of translation, or activation of an inflammatory response. If the stress cannot be resolved, cell death pathways can become activated. One of the most important integrators of cellular stress response pathways is the tumor suppressor p53 . DNA dam−/− mouse. The p73−/− mouse suffers from abnormal hippocampal development, hydrocephalus, chronic infections and inflammation, as well as abnormalities in pheromone sensory pathways [−/− mouse is even more severe. It is born alive, but dies soon after birth caused by multiple developmental defects that include limb truncations and the lack of a multilayered skin and other epithelial structures. These mouse models are in stark contrast to the p53−/− mouse which shows mostly relatively mild developmental defects such as ocular abnormalities and defects in tooth formation as well as death of ~20% of female embryos and newborn mice due to defects in neural tube closure [−/− mice are infertile due to lack of mature sperm cells. In addition, p73 is essential for the development of multiciliated cells as, for example, present in the trachea [−/− mice [The discovery that p53 has two siblings—called p63  and p73 pathways . The phe closure ,18. Thes closure ,20. Male trachea . Lack of−/− mice , which iCaenorhabditis elegans [Drosophila melanogaster [Ciona intestinalis [For p63, two different main functions have been identified: p63 is responsible for the development and maintenance of stratified epithelial tissues such as skin ,23,24, a elegans ,28, Drosnogaster ,30, Cionstinalis , or sea stinalis  express stinalis . In mammstinalis ,34. Thisstinalis ,36,37. Istinalis  that elistinalis ,40. Detestinalis . While tstinalis , which istinalis . This acstinalis  and de-pstinalis ,47,48,49stinalis  that abrstinalis  . Insteapromoter . While Δpromoter , RNAseq promoter ,58,59 aspromoter ,61,62,63−/− mouse revealed that it suffers from a lack of stratified epithelial tissues [−/− mouse has demonstrated that the maintenance of this compartment is dependent on the expression of p63 with its homozygous inactivation resulting in a disorganized pseudostratified epithelium that does not undergo full differentiation and expresses simple epithelial markers such as keratin K8/K18. Wild type skin shows a clear gradient of p63 expression with high expression in the basal layer followed by decreasing expression in more differentiated keratinocytes and loss of expression in the upper layers [−/− mouse. These tissues include esophagus, the proximal portion of the stomach, cervix, urogenital tract, prostate, and breast, as well as structures derived from the same stem cells responsible for these tissues such as mammary, sebaceous, lachrymal, and salivary glands [−/− mouse, such as the apical ectodermal ridge (AER) on the limb buds, a region of specialized, multilayered epithelium, which is essential for the development of distal limbs, digit patterning, and morphogenesis [The analysis of the p63 tissues ,23. The  tissues ,65 that r layers . In addiy glands ,23. Furtogenesis ,67, and −/− mouse not showing any obvious epidermal defects [In addition to these squamous stratified epithelial tissues, p63 is expressed also in pseudo-stratified epithelia such as the epithelium of the trachea where p63 is found in the basal cell layer . Interes defects , first r defects .The important role of p63 for the integrity of stratified epithelial tissues is tightly associated with its regulatory role in gene expression. Consistent with in vivo observations, cellular studies have shown essential roles of p63 in cell proliferation, differentiation, and cell adhesion ,72,73 inDifferent from previous expectation that p63 regulates only a few dozens of direct targets, tens of thousands of p63 binding sites  have beeTo coordinate specific transcriptional programs, p63 cooperates with other transcription factors. Cooperation with TFAP2C was observed in a study using ATACseq (Assay for Transposase-Accessible Chromatin using sequencing) experiments and transcriptome data from hESCs undergoing epidermal differentiation . In this−/− mice. Direct interaction of p63 with epigenetic factors has also been observed in the case of HDAC1/2 which bind to the C-terminal TI domain [The combination of several investigations has shown that p63 is involved in higher order regulatory mechanisms by cooperation with chromatin remodeling proteins. Among these proteins are SATB1 , a proteI domain ,85. ThisI domain ,51,104, I domain .In line with the already mentioned bookmarking role of p63 in binding to enhancers, a pioneer function role of p63 has also been proposed. Comparison of loci to which p63 is bound in keratinocytes with the same loci in other cell types has demonstrated that without endogenous p63 expression these loci are nucleosome-enriched, compact, and hence transcriptionally inactive . In keraIn summary, the data revealed by novel epigenomic technologies have consolidated the master regulatory role of p63 in stratified epithelia.−/− mouse led to the identification of mutations in p63 being responsible for several human syndromes [The publication of the phenotype of the p63yndromes ,109,110 yndromes ,112. Poiyndromes , which cyndromes . Most ofMutations responsible for the Ankyloblepharon-ectodermal defects-cleft lip/palate  syndrome are found in the C-terminus of p63  includinOther p63-related syndromes—Limb mammary syndrome , Acro-Dermato-Ungual-Lacrimal-Tooth malformations syndrome , and Rapp-Hodgkin syndrome  are similar to either the EEC  or AEC TP63 deletion develop normally [Mutations in p63 that cause the syndromes mentioned above are believed to act via a dominant negative or gain of function mechanism. Haploinsufficiency was thought not to be relevant for p63-caused syndromes. This interpretation was mainly based on the observation that individuals who have a constitutive terminal deletion of the long arm of chromosome 3, which harbors the p63 gene locus do not suffer from EEC like syndromes . This wanormally ,23. In cnormally . The twoThe Ectrodactyly, Ectodermal Dysplasia, and Cleft lip/palate syndrome is the most common and best investigated p63-related syndrome. Biochemical studies have revealed that the missense mutations in the DNA binding domain result in loss of DNA binding capability , which dDue to the master regulator function of p63, loss of DNA binding by EEC-type mutations has drastic effects on the chromatin landscape and transcriptome. Through a combination of ChIPseq and ATAC-seq analysis, it was shown that the entire enhancer landscape is changed in EEC patient keratinocytes ,62,84. WInvestigation of the defects in limb formation has revealed that Dlx5 and Dlx6 are direct targets of ΔNp63α ,126. Bot+/L514F), known from human patients to cause AEC, was created and analyzed [+/L514F epidermis and palate. In particular, the mRNA level of the epidermal specific isoforms Fgfr2b and Fgfr3b were reduced, while the levels of Fgfr1 and Fgfr4 did not show differences relative to wild type or p63+/− tissues. These results are consistent with the identification of p63 binding sites in Fgfr2 and Fgfr3 loci by ChIPseq. Epidermal cells self-renewing potential was affected both in p63+/L514F and in Fgfr2b−/− keratinocytes. Interestingly, the Fgfr2b−/− mouse shows epidermal hypoplasia, tooth and hair defects, as well as cleft palate, strongly phenocopying the AEC syndrome.The Ankyloblepharon Ectodermal defects-Cleft lip/palate (AEC) syndrome is caused by three different types of genetic variations in the p63 gene: (1) Point mutations in the SAM domain, (2) point mutations within the TI domain, and (3) frame shift mutations C-terminal to the oligomerization domain . To gainanalyzed . This muOther transcriptional p63 target genes that were found downregulated by AEC mutations, at least in human cells exogenously expressing AEC mutant p63, are HOPX, GRHL3, KLF4, PRDM1, and ZNF750 ,133, tra+/L514F mouse model [To understand the structural consequences of the L514F mutation in the SAM domain, the structure of the mutant form was determined by NMR spectroscopy and compared with the structure of the wild type domain . No signse model . Analysise model . Interesse model . Aggrega−/− mouse despite lacking functional p63 in the oocytes and required a later TA-isoform specific knock out mouse [In addition to its role as master regulator of epidermal development, p63 is the master quality control factor in oocytes  ,137,138.ut mouse . This orut mouse ,39,42. PTP63 [Some reports of the effect of p63 mutations on female fertility have started to appear in the literature. Nonsense mutations within the SAM domain  ,140 haveTP63 , leadingNrg1 is a direct transcriptional target of p63 in basal cells of the mammary gland [The p53 protein family is arguably one of the most important protein families for genetic quality control and integration of stress and repair pathways in the cell. The p73 and p63 knock out mouse studies in combination with the identification of several developmental syndromes in human patients have shed a new light on the evolutionary origin of this family. Likely, the original function was that of a genetic quality control factor in germ cells, which are virtually immortal, as germ cells are also the source of the germ cells of the following generation. Strict quality control of the genetic integrity is, therefore, important for all organisms. In the case of p63, this control function of germ cells as the most important stem cell was then transformed into its role as a master regulator of epithelial development. Despite its high sequence similarity to p53, p63 does not seem to have a tumor suppressor activity , which iry gland . As Nrg1


Epithelial organs are the first barrier against microorganisms and genotoxic stress, in which the p53 family members p63 and p73 have both overlapping and distinct functions. Intriguingly, p73 displays a very specific localization to basal epithelial cells in human tissues, while p63 is expressed in both basal and differentiated cells. Here, we analyse systematically the literature describing p63 and p73 protein–protein interactions to reveal distinct functions underlying the aforementioned distribution. We have found that p73 and p63 cooperate in the genome stability surveillance in proliferating cells; p73 specific interactors contribute to the transcriptional repression, anaphase promoting complex and spindle assembly checkpoint, whereas p63 specific interactors play roles in the regulation of mRNA processing and splicing in both proliferating and differentiated cells. Our analysis reveals the diversification of the RNA and DNA specific functions within the p53 family. The p53-family is a group of proteins, which consists of p53, p63, and p73 ,2. p63 ap53, p63 and p73 proteins are represented by multiple isoforms that regulate each other’s transcription and functions ,9. Full In the full length TAp73α and TAp63a, N-terminal TA domain acts as the transcriptional activator whereas C- terminal containing SAM and inhibitory domains repress TA activity ,12. GeneIn particular, DNA-binding domain is the most conserved structural element across the p53-family , leading to identical DNA recognition ,17,18,19Specifically, p63 and p73 play distinct roles in epithelial morphogenesis. The p63 is a major player in skin biology and its role in epidermis was thoroughly investigated during the last two decades ,37,38,39The p63 knockout in mice leads to E1 lethality and pups born with non-differentiated skin ,34. TotaIn contrast, the p73 knockout mice are characterised by runting phenotype, hippocampal dysgenesis and hydrocephalus, sterility, chronic inflammation and infection in the lungs, sinus, and ears . Total pIn the human skin, some keratinocytes fail to divide and become polyploid upon differentiation that can be induced by the DNA damage and is associated with overexpression of Cyclin E ,45. UsinIntriguingly, p73 displays a very specific localization to basal epithelial cells in all human tissue where it’s localization was determined by immunohistochemistry. In contrast, the p63 is expressed in both basal and differentiated cells ,48.The role of p63 in polyploidy has not been evaluated, however, the presence of p63 in differentiating keratinocytes suggests that p63 is not interfering with the polyploidy of these cells. At the same time, p73 suppresses polyploidy and aneuploidy in the absence of functional p53 ,49. AlsoHere, we systematically analyzed the literature describing protein interactions and functions of p63 and p73, trying to reveal their distinct functions that could be a physiological basis for their differential distribution in epithelial organs.What we found is that p73 and p63 cooperate in the genome stability surveillance in proliferating cells with the specific p73 function in the APC/C and spindle assembly checkpoint. Unexpectedly, our survey suggests a distinct function of the p63 in the regulation of mRNA processing and splicing in both proliferating and differentiated cells.http://www.proteinatlas.org ..98].In contrast to the APC/C components, p63 interacting ribonucleoproteins are found in all cells of the basal and differentiated epithelial layers. Consistent with continued presence of the p63 in the differentiated keratinocytes, it is possible to speculate that these interactions regulate differentiation-specific RNA splicing. For example, physical association of the heterogeneous nuclear ribonucleoprotein A/B (HNRNPAB) and p63a via its SAM domain led to a specific shift of FGFR-2 alternative splicing towards the K-SAM isoform essential for epithelial differentiation . In addiAnother case of the p63 mediated RNA regulation is p63 interaction with DHX9 (RNA helicase A) that is highly expressed in differentiated keratinocytes and is known to regulate circRNA formation through binding to the inverted-repeat Alu elements . The cirIn addition, the DNp63a interacts with RNA binding protein FUS , that isThus, direct and indirect evidence suggest that p63 mediated regulation of RNA metabolism influences basal and differentiation specific programs in epidermis ,152,156.The role of p73 in promoting translational elongation is recently revealed , althougThus, direct and indirect evidence suggest that p63-mediated regulation of RNA metabolism influences basal and differentiation specific programs in the epidermis ,152,156.Finally, we address a question if distinct p63 and p73 protein interactions correspond to conserved or diverse protein domains .While p63 binding sites for the p63 interacting complexes are not mapped, a lot more is known about putative p73 interacting complexes B. NotablAberrant expression of the p53 family members protein isoforms underline progression of many cancers by regulating the balance between proliferation and apoptosis ,169,170.First, cluster analysis of the protein interactions by the Metascape obtained from the open source database (Biogrid) highlights a unique role of p73 in the regulation of cell cycle and mitosis and, unexpectedly, suggests a unique role of p63 in the RNA metabolism and related cellular functions. Moreover, literature suggests that a specific p73 isoform, DNp73β, plays a dominant and yet redundant role in the basal keratinocytes differentiation and related functions, although the effects on polyploidy are yet to be analyzed.There are unresolved questions that need to be answered. While a role of the TAp73α isoform in the mitotic checkpoint is established, the role of the DNp73α isoform which is expressed in the basal keratinocytes of skin is not clear yet. Other proteins, central to SAC regulation, are expressed in the skin but details of the SAC checkpoint control which is established mostly in the cancer cell lines is likely different in the normal epithelial cells.Surprisingly, transcriptional and post-transcriptional regulation of p63 and p73 via protein–protein interactions are not well understood. Apparently, p63 and p73 isoforms regulate chromatin modifications in a cell specific and context dependent manner. Moreover, the issue is complicated by the fact that p63/p73 isoforms bind to DNA not only as transcription factors, but also as a non-DNA bound component transactivating other transcription factors . Few investigations suggest that differential activity of p63/p73 is complex with each other versus other p63/p73 specific interacting proteins switch TAp73 from anti- to pro-oncogenic activities ,21,71. T