In the last decade, PPARγ agonists—besides their known action and clinical use as insulin sensitizers—have proved to display a wide range of antineoplastic effects in cells and tissues expressing PPARγ, leading to intensive preclinical research in oncology. PPARγ and activators affect tumours by different mechanisms, involving cell proliferation and differentiation, apoptosis, antiinflammatory, and antiangiogenic effects. We recently provided evidence that PPARγ and agonists inhibit IR by non canonical, DNA-independent mechanisms affecting IR gene transcription. We conclude that IR may be considered a new PPARγ “target” gene, supporting a potential use of PPARγ agonists as antiproliferative agents in selected neoplastic tissues that overexpress the IR.The insulin receptor (IR) plays a crucial role in mediating the metabolic and proliferative functions triggered by the peptide hormone insulin. There is considerable evidence that abnormalities in both IR expression and function may account for malignant transformation and tumour progression in some human neoplasias, including breast cancer. PPAR S6k is also stimulated by TOR, which induces the translation of cell-cycle regulators, such as cyclin D, mediating progression through the G1 phase. Cyclin D is also a target for the Ras/ERK cascade induced by insulin, leading to a synergistic effects on cell proliferation [The peptide hormone insulin regulates the metabolism and growth of most cells . In targferation –12  system  implicatα (activator protein 2-α) accounted for increased IR expression in neoplastic breast tissue [α represented a fundamental prerequisite for AP-2α to activate IR gene transcription in neoplastic breast tissue. Similarly, a functional link between IR, and cyclin D1 has been recently described in pancreatic cancer [Dysfunctional IR signaling is implicated in certain common dysmetabolic disorders, including obesity, type 2 diabetes, the dysmetabolic syndrome X, and the polycystic ovary syndrome –19. Alsot tissue . In thesc cancer . Thus, ac cancer , 33.β. By potentiating the recruitment and binding of Sp1 and C/EBPβ to the IR promoter, HMGA1 greatly enhances the transcriptional activities of these factors in the context of the IR gene [β requires the assembly and cooperation among these various nuclear factors at the levels of the two AT-rich sequences of the IR gene promoter, C2 and E3, which have a significant ability to drive transcription when introduced into mammalian cells [In target cells the IR has been shown to be under the regulation of hormones, metabolites, and differentiation . To furt IR gene , 36. Traan cells , 35, 36.an cells . Overexpγ is a nuclear hormone receptor [γ plays a number of pleiotropic effects, that include a critical role in placental vascularization, myocardial health, and embryonic development [γ generally exterts its biological function as heterodimer with the retinoid-X-receptor through binding to a specific cis-acting sequence on DNA—a peroxisome proliferator response element (PPRE)—to initiate transcription [γ requires activation by binding its ligand. The PPARγ activators identified so far include naturally occurring compounds, as some unsaturated fatty acids, some anti-inflammatory molecules—such as a prostaglandin J2 metabolite —, oxidized low-density lipoprotein (LDL) particles 9-and 13-HODE  [γ belong to the pathway of metabolism and transport of lipids [γ may also repress gene transcription. In monocytes and macrophages, for example, it reduces IL-4 (interleukin-4) expression. Also, it reduces proinflammatory proteins, like (tumor necrosis factor α) TNF-α, (interleukin-1) IL-1, (inducible nitric oxide synthetase) iNOS, and proinflammatory transcription factors such as (activator protein-1) AP-1,  STAT, and (nuclear factor-kB) NF-kB [γ can form weak interactions with (nuclear receptor corepressor) NcOR and (silencing mediator of retinoid and thyroid hormone receptors) SMRT to repress target gene expression [γ are still largely undefined and can be related to a wide range of processes including tumour cell differentiation, apoptosis, anti-proliferative effects, and modulation of angiogenic phenotype of the tumour microenvironment.PPARreceptor –39 highlreceptor –42. It ireceptor –46. Besielopment , 48. It elopment –51. PPARcription , 50. To ic acid) , 49, andic acid) , a classic acid) , 53. MosB) NF-kB –56. The pression . Target γ have been performed in several cultured cell lines expressing variable amounts of PPARγ. In HepG2 human hepatoma cells IRs are relatively abundant, while endogenous PPARγ is barely detectable. Protein expression studies showed that IR protein content was considerably reduced in HepG2 cells overexpressing PPARγ (~50% less than control cells), and this reduction was more pronounced in PPARγ-overexpressing cells exposed to TZDs. It has been postulated that PPARγ could affect IR content by blunting IR gene transcription. To this end, reporter gene studies have been performed using the pIR-CAT recombinant vector that contains the entire 5’-flanking region of the human IR gene [γ in HepG2 cells transfected with pIR-CAT determined a ~50% reduction in CAT activity that was similar to the reduction observed in cells exposed to rosiglitazone alone, and resulted more marked in PPARγ-overexpressing cells simultaneously treated with TZD rosiglitazone. These findings were confirmed in PPARγ overexpressing MCF-7 human breast cancer cells, a cell line naturally expressing only detectable levels of PPARγ [γ [γ, and TZDs, either alone or in combination, inhibited pCAT-C2 activity to the same extent than they did in HepG2 cells transfected with the full-length pCAT-IR promoter, indicating that interference of PPARγ and agonists with IR gene-transcription machinery occurs at the level of the proximal promoter region, C2. This conclusion was supported by the observation that in experiments using the pCAT-E3 reporter vector, containing the more distant E3 sequence of the IR gene, no effects on CAT activity were observed in cells exposed to PPARγ and/or TZDs. However, no PPRE have been identified on the promoter region of the IR gene. A similar observation has been previously provided by us for the transcription factor AP-2α, for which DNA-binding activity was undetectable within the IR gene promoter, and transactivation of the IR gene by AP-2α occurred indirectly through physical and functional cooperation with HMGA1 and Sp1 [γ could perturb IR gene transcription via noncanonical mechanisms interfering with the “enhanceosome” complex formation implicated in transcriptional activation of the IR gene. This hypothesis was confirmed by GST-pull-down studies, followed by electrophoresis mobility shift assay and chromatin immunoprecipitation analyses, demonstrating that PPARγ physically interacted with Sp1, AP-2α (in selected cell lines) and, to a lesser extent, with C/EBPβ and prevented binding of AP-2α to Sp1 protein, as well as of Sp1 and C/EBPβ to their DNA consensus sites within the IR gene locus [Studies aimed at understanding whether IR could constitute a target gene for PPAR IR gene . Forced of PPARγ , and 3T3PPARγ [γ . ExposurPPARγ [γ . When th and Sp1 . Therefone locus .γ may adversely affect IR gene transcription in the absence of PPRE on the IR gene promoter. By causing a displacement of Sp1, AP-2α, and C/EBPβ, PPARγ may play significant molecular roles in the transcriptional activities of these factors in the context of the IR gene, both in physiology and pathology  tumor suppressor gene [γ and its agonists may induce their antiproliferative effects is not fully understood yet. Recently, non-genomic cross-talks between PPARγ and cytoplasmic proteins, like  ERK 1/2, and (mitogen-activated protein kinase) MAPK kinases, have been reported in cancer cells and functional importance has been given to the subcellular localization of PPARγ [We showed that PPARin genes –67. The ng genes . Many posor gene –70. Howeof PPARγ , 72. In of PPARγ . Therefoγ agonists inhibit cyclin D1 [γ support the conclusion that PPARγ and TZDs may interfere with the hormonal control of the cell cycle, at least in part, through the inhibition of the IR. Over the last decade, PPARγ has emerged as an important drug target in type 2 diabetes mellitus [γ, providing further evidence for the use of TZDs as anti-proliferative agents in selected tumours overexpressing the IR.The last three decades of medical research examining the molecular pathogenesis of cancers have provided compelling evidence for the universal disruption of the cell cycle in human tumours, and recent studies have demonstrated a critical interface between hormonal signaling and the cell cycle . In thisyclin D1 . Our finmellitus , and TZDmellitus , a possimellitus . Thus it


Thaumetopoea pityocampa sensu lato) as an example, these needs were met by combining species niche modelling, dispersal modelling, host impact and economic modelling. Within its native range (the Mediterranean Basin and adjacent areas), T. pityocampa causes significant defoliation of pines and serious urticating injuries to humans. Such severe impacts overseas have fuelled concerns about its potential impacts, should it be introduced to New Zealand. A stochastic bioeconomic model was used to estimate the impact of PPM invasion in terms of pine production value lost due to a hypothetical invasion of New Zealand by T. pityocampa. The bioeconomic model combines a semi-mechanistic niche model to develop a climate-related damage function, a climate-related forest growth model, and a stochastic spread model to estimate the present value (PV) of an invasion. Simulated invasions indicate that Thaumetopoea pityocampa could reduce New Zealand’s merchantable and total pine stem volume production by 30%, reducing forest production by between NZ$1,550 M to NZ$2,560 M if left untreated. Where T. pityocampa is controlled using aerial application of an insecticide, projected losses in PV were reduced, but still significant . The PV estimates were more sensitive to the efficacy of the spray program than the potential rate of spread of the moth. Our novel bioeconomic method provides a refined means of estimating potential impacts of invasive alien species, taking into account climatic effects on asset values, the potential for pest impacts, and pest spread rates.Biosecurity agencies need robust bioeconomic tools to help inform policy and allocate scarce management resources. They need to estimate the potential for each invasive alien species (IAS) to create negative impacts, so that relative and absolute comparisons can be made. Using pine processionary moth ( Invasive alien species (IAS) are a major problem worldwide. Despite the efforts of biosecurity agencies and an international phytosanitary legal framework for the management of invasion pathways, the rate at which these species are invading new territories appears to be increasing rapidly The rate of biological invasions has fuelled demands from biosecurity agencies for information on the potential distribution and impacts of IAS in terms of economics, human health and biodiversity. Climate has long been recognised as an important environmental determinant of the distribution of pests could establish within its jurisdiction, but another to be able and willing to respond to it should an incursion eventuate. IAS incursion responses are costly, and agencies have a finite capacity to respond. When faced with an incursion, they must decide whether to 1) attempt an eradication, 2) develop a campaign to slow the spread of the organism, 3) attempt to contain it, 4) allow the organism to spread without a coordinated response, and let land managers and local authorities manage the organism to reduce impacts to acceptable levels, or 5) allow the organism to spread, but mobilise a coordinated response such as a biological control programme It is one thing for a biosecurity agency to know that a pest Despite their common use in pest risk assessment, the potential of process-based niche models to inform these responses has not yet been fully realised. Although potential distribution is a useful input to pest risk assessment, in that it delineates an area in which the pest could potentially be problematical Thaumetopoea pityocampa and T. wilkinsoni (Lepidoptera: Thaumetopoeidae) T. pityocampa) to refer to the species complex, T. pityocampa sensu lato. Thaumetopoea pityocampa cause major defoliation of pines across southern Europe and around the Mediterranean Sea. Previous research has described the climatic requirements of T. pityocampaIt has been proposed recently that pine processionary moths are a species complex that consists of two species: T. pityocampa than natural woodlands Pinus radiata appears more susceptible to attack by T. pityocampa than native European Pinus spp. Artificial woodlands appear more susceptible to attack by T. pityocampa has been shown to result in growth reductions of up to 83% T. pityocampa be accidentally introduced into the southern hemisphere where its preferred host P. radiata is the most widely planted of all plantation species T. pityocampa as it has a significant plantation resource (1.8 million ha), of which approximately 90% comprises P. radiataAlthough the relationship between climate and host damage has not yet been quantified, defoliation of pines by T. pityocampa on volume and present value of the plantation estate under current climate, assuming control or no control of T. pityocampa using insecticide. Finally, we discuss the utility of this case study as a generic approach for quantifying economic impacts of pests on important crop species.In this contribution we demonstrate a novel analytical framework combining ecological and economic modelling, to estimate the economic impacts of an invasive organism as a basis for informing policy-level decision-making. We use New Zealand as a case study, and simulate the impact of an invasion by T. pityocampa, 3) a climate-based host damage function, 4) a spread model and 5) a partial budget economic model.The analytical framework consists of five components, 1) a climate based host productivity model, 2) a niche model describing the climate suitability for the pest species, P. radiata at age 30 years with a reference stem density of 300 stems ha−1  for ems ha−1  [32], , and 3) Good control: invasion by T. pityocampa that is managed effectively (mr reduced by 95%). For the three scenarios in which Btk is applied it is assumed that the insecticide completely negates the negative impact of T. pityocampa on growth over the area occupied by the moth.In total, five scenarios were examined. The first two assumed that et al.mr (the maximum rate of population growth) and μ (the rate at which satellite populations are generated each year) were then sampled from uniform distributions described in For each invasion scenario a set of simulations were run using the spread model of Waage T. pityocampa to fly 20 km T. pityocampa over 32 years in the comparatively flat Paris Basin indicated an average annual radial rate of spread of 2.7 km yr−1, though more recently rates of 5.6 km year−1 have been observed T. pityocampa larvae were able to survive conditions colder than presently occupied, which indicates that the observed spread could be limited by the dispersal rates of the female moths, and the present range is lagged behind the retreating climatic limits. The diffusion coefficient in D is the diffusion coefficient (ha yr−1), and MDD is the average radial rate of spread (5.6 km year−1), which yields a value of 1 996 ha year−1.Whilst it is possible for male moths of et al.Pieris rapae exhibited significant acceleration in its range expansion that indicated that long-distance jump dispersal was likely to be a significant factor in its invasion. In that survey, observed rates of radial range expansion were predominantly less than 10 km yr−1, which agrees with the estimate from Battisti et al In a survey of spread rates for 27 Lepidoptera, Waage et al.T. pityocampa. They found that the fecundity of a winter population of T. pityocampa was 197.4±45.4, with 98.4±1% viability. Whilst Pimentel et al.T. pityocampa. Predation resulted in approximately 5% of nests having no survivors, with survival of larvae in other nests of 32.2±22.8%. Taken together, these results indicate an average value for the net reproductive rate, r of approximately 1.47 year−1, derived using F is average fecundity of each egg batch (197) FR is the (assumed) female sex ratio for eggs (0.5), V is average egg viability (0.98) NestPredationS is the assumed average fraction of nests with at least one survivor (0.95), LarvalPredationS is the average fraction of larvae surviving predation (0.32) M is the assumed mating success rate (0.05). The value of M for the No Control scenario was selected after consideration of the observed mating success rate for gypsy moth (Lymantria dispar L.) under low density conditions such as those experienced in the region of the invasion front L. dispar studied by Robinet et al. shares with T, pityocampa the qualities of highly mobile males and sessile females T. pityocampa, the females lay a single batch of eggs; colonies are formed from one or several batches of eggs mr included in the model of Waage et al.r –1 as it is included within a difference equation framework, hence a value of 1.45 for r is equivalent to a value of 0.45 for mr. The carrying capacity of pine forests for T. pityocampa is estimated to be 0.95 nests per tree×1 000 trees ha−1×1 adult female per nest. It was assumed that only one female reaches the adult stage.Pimentel T. pityocampa (μ) was very low  planted to forest in each cell and iMAI is the area-weighted average 300 Index value in m3 ha−1 yr−1, and FO is the outbreak or attack frequency reported by Laurent-Hervouet T. pityocampa (0.5 yr−1), and n is the total number of 10′ cells in New Zealand that are climatically suitable for T. pityocampa under historical conditions.The total potential loss to pine plantations from LGVP, was calculated as,SV is the stumpage value (presently NZ$55.00).The present gross value of this production loss −1 (ca. 60 € ha−1) T. pityocampa on crop volume growth.We assumed that Btk was applied aerially to infested forests throughout the 30 year period, at a cost of NZ$120 haT. pityocampa on the tree growth rates across the New Zealand plantation estate was then estimated using discounted cashflow analysis. Analyses were undertaken to estimate discounted annual losses over a 30 year period from 2010 to 2040 (the invasion was assumed to start in 2010). In this analysis, it was assumed that forest rotations and harvests would occur on a rolling basis and so the forest age class would have a stable distribution. The discount rate used was 7% per annum.Under each scenario, the impact of T. pityocampa, the CLIMEX Ecoclimatic Index was compared with the reported distribution in Europe and North Africa  losses ranged from NZ$1,550 M to NZ$2,560 M . Under tffective .T. pityocampa compared with doing nothing  scenarios with a low rate of spread due to effective control  and gum leaf skeletoniser (Uraba lugens). Even if T. pityocampa did not become established in New Zealand in the near future, the rate of defoliator introductions in New Zealand and overseas indicates that there is a high risk of such an invasion. Ultimately, this study should serve as a case study of a potentially invasive insect pest of pines.Accidental shipments of T. pityocampa is extensive . These mostly sub-tropical regions experience climates that have less extreme seasonality than that of the Mediterranean basin. This curiosity may be explained by the fact that the native range of T. pityocampa is geographically isolated from areas with a sub-tropical climate, and should it invade such a region with a less extreme climate than its native range, it may indeed thrive. However, whilst suitable hosts are grown in these regions , indicating some degree of likely climate suitability, it is prudent to treat climate suitability projections in these areas with some added caution as there may be some negative life-history factor associated with warm-wet conditions that have not been taken into account in the niche model.The niche model indicates that the global potential distribution of xtensive , and incT. pityocampa, and to construct the climate-based growth impact function. Combining the 300 Index values, the CLIMEX niche model and the growth impact function allowed us to quantify potential tree growth rate impacts in a spatially-explicit and defensible manner, and to identify regions of highest priority for protection. The growth impact function is a relatively simple technique that captures climatic variability in pest suitability without resorting to the complicated and expensive method of modelling the pest population dynamics directly. By including consideration of the rate of spread of the pest, the potential costs were discounted appropriately, and the different control strategies that affect the spread rate could be evaluated.Compared with traditional economic pest risk assessments, the method demonstrated here offers significant enhancements. Traditional cost-benefit approaches ignore variability in pest population dynamics due to differences in climate throughout the area in which the vulnerable crops are grown. Typically, these analyses do not even use a species niche model for the pest to estimate which cropping regions are vulnerable to pest impacts. The CLIMEX model allowed us to identify which forests were vulnerable to attack from www.mapspam.info , Eurostat , and Cropscape (USA)]. The spatial resolution of the crop productivity maps are typically coarser than the 300 Index surface, though they appear adequate for combining with niche models for the type of analysis described here.The data requirements for this project were significant, and it is unlikely that this type of analysis would be undertaken routinely for pest risk assessments. Of the different information components required to undertake this analysis, the CLIMEX analysis could be considered the most practiced and available. Whilst high quality fine resolution modelled productivity surfaces such as the 300 Index dataset are likely to remain rare, crop productivity maps based on crop production statistics are becoming more commonplace [e.g., The climate-impact function is an attractive compromise between expensive detailed process-based population dynamics modelling on the one hand, and using a simplistic estimate of average pest impacts on the other. For relatively little effort, it provides a means of spatially matching pest impacts with productivity. As with the niche model, having generated the model once, it is able to be applied to pest risk assessments in any jurisdiction. However, for this type of analysis to become more commonplace, reporting of pest impact would be best studied and reported using standardised methods and measures.Discounting the costs throughout the simulated invasion had a significant impact on the cost estimates, so it is clearly desirable to include plausible estimates of the rate of spread of invaders throughout pest risk areas. To do this routinely, the potential rates of spread of pests across landscapes may need to be better studied and documented. Whilst it is inconceivable that there would ever be a useful library of documented pest spread rates for every pest of economic concern, it is possible that a study of spread rates for different organisms could be used to develop a useful trait-based means of estimating useful rates of spread classes for invasive species.The method of linking climate suitability, spread rates and host-impact demonstrated here appears useful and practical for estimating the potential costs of invasive pests. Whilst it has been applied to a case where impacts are considered for a single host crop, it can be easily extended to accommodate multiple hosts, so long as the impact functions can be calibrated for each crop, and the abundance of each crop is known throughout the pest risk area. The method described here can also be readily applied to pests threatening non-productive assets such as natural ecosystems using appropriate pricing mechanisms such as the hedonic pricing technique or the valuation of ecosystem services. Linking the niche modelling and economic analytical tools together as we have done in this paper provides an open and transparent means by which different pest threats can be gauged in terms of their likely economic impacts, and allows different pest threats to be compared.


Approximately 20%–25% of patients with breast cancer demonstrate amplification of the human epidermal receptor type 2 (HER2) gene, resulting in an overexpression of the HER2 receptor. This overexpression is associated with aggressive disease, relatively poor prognosis, and worse clinical outcomes. Neoadjuvant therapy is the standard treatment in patients with locally advanced, inflammatory, or inoperable primary breast cancer. It is generally used to downstage the tumors and therefore to improve surgical options including breast-conserving surgery rather than mastectomy. It has been confirmed that patients with pathological complete response (pCR) to neoadjuvant treatment have better disease-free survival (DFS) and overall survival (OS). Neoadjuvant treatment can also serve as in vivo test of sensitivity to the used therapeutic regimen. The preferred neoadjuvant approach to patients with HER2-positive breast cancer is a sequential anthracycline-taxane-based chemotherapy in combination with trastuzumab. Addition of other anti-HER2 agents has increased pCR rate up to 75% and will probably become a new therapeutic direction. In the first part of this paper, we summarize the information about HER2-positive breast cancer, the various treatment possibilities, and the results of the major neoadjuvant trials. The second part focuses on the data concerning the importance of pCR and the potential risk of cardiotoxicity associated with this treatment. HER2 belongs to the epidermal growth factor receptor (EGFR/ErbB) family of receptor tyrosine kinases. This family consists of four receptors—HER1, HER2, HER3, and HER4—which are involved in regulating cell growth, survival, and differentiation. HER receptors are inactive monomers, and to activate signaling pathways, they have to undergo dimerization. Pairing among the molecules of the same HER receptor is called homodimerization; pairing of different HER receptor subtypes is called heterodimerization. HER dimerization leads to activation of two important signaling pathways—PI3K/Akt and Ras/Raf/MEK/MAPK . Other important parameters identified as predictors for pCR were HER2-positive disease, higher grade, younger age, non-lobular-type tumors, and smaller tumor size.The integrated meta-analysis  on data More recent pooled analysis of German neoadjuvant studies has also revealed different prognostic value of pCR . In patiIt has been shown that the estrogen receptor pathway might be a relevant escape mechanism in “triple-positive” tumors . AccordiIn the case of HER2-positive/ER-negative tumors, the gene expression analysis of 114 samples from the NOAH study revealed that the high expression of the plasma cell metagene and the 8q22 amplicon, and low expression of the insulin-like growth factor metagene, were associated with higher pCR rates in this group of patients treated with trastuzumab and chemotherapy .HER2 overexpression induces an activation of signaling pathways including the PI3K/Akt. Some studies have shown that patients with a low expression of PTEN or PI3K mutations have poorer response and worse clinical outcome with trastuzumab-containing therapy –49. The GeparQuattro and GeparQuinto trials showed a positive association between pCR rates and serum HER2 levels [The extracellular domain of the HER2 protein can be detected in peripheral blood as serum HER2, which can be measured by ELISA. 2 levels , 51. Butγ receptor polymorphisms [Other biomarkers such as circulating miR-210 levels , fragmenorphisms , and genorphisms  have beeIntensive studies have also been done on the markers potentially associated with resistance to trastuzumab. One is p95HER2 (truncated form of HER2 receptor), which was thought to be associated with resistance to trastuzumab but responsiveness to lapatinib, but the results from the studies are controversial. In the CHER-LOB study, the pCR rate was not different for patients with p95HER2-positive or -negative tumors . On the Other potential markers of resistance to trastuzumab as p-4EBP1—an activator of the mTOR pathways and ALDH1—a stem cell marker, were investigated in patients included in the GeparQuattro study, but their further validation is needed .Cardiac toxicity is an important side effect of trastuzumab treatment and has been observed in patients who received trastuzumab as a single agent or in combination with chemotherapy for metastatic disease and in primary breast cancer , 59.The data concerning cardiac events differ from one clinical study to the next. This is a result of different variables such as applied therapy regimens, inclusion and exclusion criteria, and time interval between anthracycline-based chemotherapy and trastuzumab treatment.In the two randomized neoadjuvant trials , 33, traIt has been proved that administration of trastuzumab concurrent with anthracyclines is associated with an increased risk of cardiac toxicity, but this risk can be manageable if the cumulative dose of anthracycline is kept low and/or less-cardiotoxic anthracyclines are used , 60–62.It is well known that the cardiotoxity of anthracyclines and trastuzumab differs in many ways. Trastuzumab can cause cardiac dysfunction identified as type II, which seems not to be dose related; it is higher when trastuzumab is given concurrently with anthracyclines, it seems to be reversible when trastuzumab is discontinued, and it is mostly medically manageable with regular medication for heart failure.On the other hand, anthracyclines produce a cardiotoxicity identified as type I, which is dose dependent, not reversible, and results in ultrastructural abnormalities, as observed in myocardial biopsies.It is very important to consider the risk of cardiac toxicity and reduce it by close monitoring of patients. We should avoid using trastuzumab in patients with a baseline LVEF lower than 50%. Extreme caution should be taken with patients older than 65 and in patients with baseline LVEF 50%–55%. We do not know exactly whether typical cardiac risk factors  are also risk factors for trastuzumab-related cardiotoxicity. Seidman et al.  performeResults of retrospective clinical experience studies suggest that advanced age, hypertension, radiation therapy to the left chest wall, or previous exposure to anthracyclines did not result in a higher risk for trastuzumab-related cardiotoxicity . On the These results have to be applied with caution as, in another study, smoking, family history, hypercholesterolemia and diabetes, and radiation to the left side of the chest were not identified as risk factors . ConditiFor identification of trastuzumab-related cardiotoxicity, all patients treated with this agent should, a part from a clinical examination with electrocardiogram, undergo the measurement of LVEF at baseline of trastuzumab treatment. Furthermore, it is recommended that LVEF be monitored every 3 months during trastuzumab treatment.Biomarkers such as NT-proBNP and troponin I are being intensively studied as potential parameters for trastuzumab-induced cardiotoxicity, but more evidence is needed before their application in the routine practice.HER2-positive breast cancer presents a heterogeneous group of diseases with various biological characteristics and clinical outcomes . The manThe neoadjuvant approach offers the possibility to reach operability in an initially inoperable disease and, in some cases, breast conservation instead of mastectomy. It also has prognostic value as patients who achieve pCR have favorable long-term outcome. The response to neoadjuvant treatment informs us of the efficacy of the used therapeutic regimen and, therefore, helps us to choose an appropriate treatment strategy. Neoadjuvant treatment requires a multidisciplinary approach, and close cooperation between surgeon, medical oncologist, radiation oncologist, and pathologist is needed.Nowadays, sequential anthracycline-taxane-based chemotherapy in combination with trastuzumab is considered the preferred therapy for HER2-positive breast cancer in a neoadjuvant setting. However, based on the results of these trials, the dual blockage of HER2 receptor has revealed significant efficacy and presents a new therapeutic approach. Other anti-HER2 agents are under intensive investigation.HER2 can stimulate angiogenesis through vascular endothelial growth factor upregulation. Therefore, HER2 blockage, together with inhibition of angiogenesis, could be another treatment option. In phase II study, neoadjuvant therapy with nab-paclitaxel, carboplatin and bevacizumab led to a pCR rate comparable to that found in chemotherapy/trastuzumab combinations .There are many questions to be answered, for example, what is the best combination of anti-HER2 agents and with which cytostatic agents; can dual-blockage of HER2 replace the chemotherapy in some cases; and what are the reliable biomarkers for anti-HER2 therapy? Much is still to be done and other large studies are needed.


The area of HER2-positive breast cancer is a rapidly changing field. The use of the humanized monoclonal antibody, trastuzumab, significantly improved the prognosis for patients with HER2-positive breast cancer, however, increasing knowledge regarding mechanisms of resistance to trastuzumab have come to light, prompting research into additional methods to target the HER2 protein. The purpose of this article is to discuss evidence for why continued blockade of the HER2 pathway continues to be important despite progression on trastuzumab, as well as to review additional HER2-targeted therapies and progression in the central nervous system. With the availability of new drugs comes the need to determine the appropriate therapeutic combinations and optimal order in which to deliver these therapies. This review summarizes the practice-changing phase III trials and some supporting phase II data regarding the various targeted HER2 therapies available for patients with advanced HER2-positive breast cancer, proposes order for anti-HER2 therapy in the advanced HER2-positive breast cancer patient, and includes information on future strategies. While other reviews on HER2-targeted therapy are available, this review specifically aims at addressing treatment options after trastuzumab failure in the patient with advanced HER2-positive breast cancer. The Human Epidermal Growth Factor Receptor 2 (HER2) oncogene is responsible for encoding a transmembrane tyrosine kinase which is over expressed in 20–25% of breast cancers and is associated with a worse prognosis ,2. The uRecent evidence suggests that activation of the HER2 signaling pathway continues to be the primary driver of tumor growth and survival, even after prolonged exposure to trastuzumab. Multiple resistance mechanisms have been proposed, and include up-regulation of ligand-induced receptor activation, increased signaling from other HER family receptors, and activation of the phosphatidylinositol triphosphate kinase (PI3K) pathway with loss of phosphatase and tensin homolog (PTEN) –8. GivenTrastuzumab is a humanized monoclonal antibody which binds to the extracellular domain of the HER2 molecule . ProposeThe German Breast Group 26/Breast International Group 03–05 trial was the first and only randomized, prospective trial to evaluate the efficacy of use of trastuzumab beyond progression on a previous trastuzumab-containing regimen . Patientpost-hoc analysis of this study was performed comparing continued HER2-targeted therapy as second or third line therapy in the form of trastuzumab or lapatinib versus chemotherapy alone [An additional py alone . In thisThe first HER2-targeted therapy to receive FDA approval after trastuzumab was lapatinib. Lapatinib is a small molecule, oral tyrosine kinase inhibitor of both HER2 and Epidermal Growth Factor Receptor (EGFR), and was initially shown in pre-clinical models to be effective in tumors resistant to trastuzumab ,16. A phLapatinib is also FDA-approved in combination with letrozole as first-line treatment for post-menopausal patients with metastatic HER2-positive, estrogen receptor positive breast cancer based on a phase III randomized placebo-control trial . Over 12p=0.008) [Additional studies performed with lapatinib in combination with trastuzumab in the metastatic setting after progression on trastuzumab have been performed. Blackwell et al. performed a phase III randomized international trial comparing lapatinib alone to the combination of lapatinib and trastuzumab in 296 patients . Patientp=0.008) . Additiop=0.008) . There wp=0.008) . With rep=0.008) . Rash wap=0.008) . It is ip=0.008) .Lapatinib is an active agent in patients with evidence of progression on trastuzumab, and is a safe and tolerable second-line anti-HER2 drug. It is important to note that it is unknown what – if any – activity lapatinib will have after progression on other next-generation HER2-targeted therapies such as pertuzumab and T-DM1, and further clinical trials to determine the correct timing of lapatinib therapy are warranted.The next agent approved for metastatic HER2-positive breast cancer was pertuzumab. Pertuzumab is a humanized monoclonal antibody which binds to the dimerization domain of HER2, thereby inhibiting dimerization with the other members of the HER family of receptors. In the international, randomized, double-blind, phase III CLEOPATRA trial, the addition of pertuzumab to trastuzumab plus docetaxel was studied in patients with newly metastatic HER2-positive breast cancer, 40–47% of who received previous trastuzumab . The addPertuzumab was also studied in combination with trastuzumab, without the addition of chemotherapy. A phase II study evaluated the combination of pertuzumab and trastuzumab in HER2-positive breast cancer patients after progression on a trastuzumab-based therapy in the metastatic setting. An overall response rate of 24.2% and a clinical benefit rate of 50% were observed . All 29 N-maleimidomethyl Cyclohexane-1-Carboxylate (MCC). This linker is thought to help isolate exposure of DM1 to the target cells and spare normal tissue from the toxicity associated with cytotoxic chemotherapy. DM1 is a derivative of maytansine 1, and works by binding to tubulin and inhibiting microtubule assembly [T-DM1 is the most recent anti-HER2 agent found to have considerable activity in patients with trastuzumab-resistant disease. T-DM1 is an antibody-drug conjugate which links trastuzumab to DM1 via a thioether linker called assembly ,27. In aassembly . Hypokalassembly . An addiassembly . The EMIassembly . At a foassembly . ImportaThese questions are becoming increasingly important as treatment for metastatic breast cancer may include multiple years of therapy. A small single institution study retrospectively analyzed HER2-positive metastatic breast cancer patients who had received T-DM1 and were subsequently administered additional anti-HER2 targeted agents after T-DM1 use . The invStandard anti-HER2 therapy with trastuzumab results in a failure to adequately treat and prevent CNS progression, resulting in a growing population of HER2-positive patients with limited therapeutic options . CNS metAlthough trastuzumab has poor blood-brain barrier penetrance, there is evidence to suggest that alteration of this barrier with whole brain radiation allows for increased concentrations of the drug . There iLapatinib shows promising activity in patients with CNS progression. In a phase 3 randomized trial of capecitabine versus capecitabine plus lapatinib in patients with locally advanced or metastatic HER2-positive breast cancer, there was a trend toward decreased CNS metastasis in the group that received lapatinib, although the difference was not statistically significant . While tTwo oral small molecule inhibitors of the HER family of receptors are in early study. Neratinib is an inhibitor of HER1, HER2 and HER4. A small phase II study evaluated neratinib in two cohorts of patients with advanced HER2-positive breast cancer, one of which had received prior trastuzumab, and the other which had not received trastuzumab . At 16 wInhibition of enzymes in the phosphatidylinositol-3-kinase (PI3K) pathway, specifically the class I enzymes, is also being heavily studied, as this pathway is involved in regulation of cell proliferation, survival and apoptosis . The panWhile patients with HER2-positive breast cancer previously had poor outcomes, the use of trastuzumab has significantly improved their survival. As resistance mechanisms to trastuzumab have come to light, many additional targeted agents as well as drug combinations have been developed and shown to have efficacy in both disease free and overall survival.


Since 2005, major progresses have been made in the neoadjuvant treatment of HER2-positive breast cancer. Trastuzumab introduction associated with chemotherapy has been the first major step leading to the improvement of the complete pathological response rate and, like in the adjuvant studies, better survivals. Dual HER2 blockade has been the next step and trastuzumab is associated now with other anti-HER2 therapies like lapatinib or pertuzumab, the latter being much more easy to use in combination with chemotherapy. Additional knowledge is necessary to better define within the HER2 tumor subgroup which patients could benefit more from targeted therapies. Different biomarkers have been studied to predict the response after anti-HER2 neoadjuvant therapies but until now none has been validated. Neoadjuvant chemotherapy in breast cancer treatment is now recognized as a standard care to increase conservative surgery , 2. Its In HER2-positive breast cancer, randomized studies with and without anthracyclines have demonstrated the essential role of anti-HER2 therapies in obtaining increased pathological complete response rates and good long-term results.P = 0.036). In the HER2-positive subgroup (n = 90), the addition of trastuzumab to the chemotherapy increased the pCR rate (40% versus 26.7%) but this result was not statistically significant (P = 0.37). Authors suggested it might be due to the unexpectedly high rate of pCR achieved in the ED/EDC group . The lowest pCR rate is reported by Pierga et al. [Several randomized trials have evaluated, in the neoadjuvant setting, the role of trastuzumab , a recombinant humanized monoclonal antibody that targets HER2 receptor. The first randomized trial in patients with operable noninflammatory disease was stopped early when the pathological complete response (pCR) rate in the trastuzumab group was more than twice as high as that of the control group (65% versus 26%) , 5. The roup n = 0, the adIn the GeparQuattro study, 445 patients with HER2-positive tumors were scheduled to receive 4 cycles of epirubicin plus cyclophosphamide and then were randomly assigned to either 4 cycles of docetaxel or 4 cycles of docetaxel plus capecitabine or 4 cycles of docetaxel followed by 4 cycles of capecitabine . All patDespite improvement of pCR rates, all patients do not equally benefit from trastuzumab therapy. Indeed multiple pathways can contribute to acquired or intrinsic resistance to trastuzumab , 22. LapTrastuzumab and lapatinib have well-characterized synergistic interaction in HER2-positive breast cancer models –27, due Lapatinib leads also to an accumulation of HER2 at the surface of the cell, enhancing trastuzumab-dependent ADCC , 28. TheThe direct comparison in the GeparQuinto trial showed that pCR rate with chemotherapy and lapatinib (30%) was significantly lower than that with chemotherapy and trastuzumab (44%) . The resP = 0.01) [In the NeoALTTO study, pCR rate was significantly higher in the group given lapatinib and trastuzumab (47%) than in the group given trastuzumab alone (28%) . The res = 0.01) .P < 0.001) [P = 0.0141; 16.8% (arm C) and 24% (arm D). The superiority of the pertuzumab-trastuzumab arm either in first-line metastatic setting or in the neoadjuvant setting leads to the initiation of the ongoing adjuvant trial with pertuzumab (NCT01358877). Pertuzumab  is a humanized monoclonal antibody directed at the dimerization domain of HER2. Pertuzumab and trastuzumab have complementary mechanisms of action due to their distinct binding sites. Pertuzumab inhibits ligand-dependent signaling particularly between HER2 and HER3 which is known to activate a proliferation pathway . Pertuzu< 0.001) . NeoSphe< 0.001) . Three hP = 0.82) [In a recent meta-analysis, Valachis et al. studied the overall effect of neoadjuvant trastuzumab on BCS . Breast- = 0.82) . This co = 0.82) . In another meta-analysis, Valachis et al. reported the effect of lapatinib versus trastuzumab or the combination (lapatinib plus trastuzumab) versus trastuzumab on the BCS rate . They foMoreover, other criteria can influence the BCS rate and must be taken into account like the tumor size, the presence of in situ carcinoma, the multifocality of the lesion, and the preference of the patient. Unfortunately, these data were not reported in the different studies. P = 0.013), although 19 (16%) patients with HER2-positive disease assigned to chemotherapy alone crossed over to receive adjuvant trastuzumab [P = 0.114) [Most of the studies in this review did not report data of survival. In the NOAH trial, the primary end point was the event-free survival (EFS) . Adjuvanstuzumab . Benefit= 0.114) .P = 0.041) after a median followup of 36.1 months [Buzdar et al. reported a better disease-free survival (DFS) among patients randomized to chemotherapy plus trastuzumab compared to patients with chemotherapy alone , after an anthracycline- and taxane-based therapy without trastuzumab [Estrogen-receptor- (ER-) negative tumors are usually associated with a higher pCR rate compared to ER-positive tumors –39 inclustuzumab .In neoadjuvant trials with trastuzumab or others anti-HER2 therapies, similar results are described. The pCR rates in HR+ and HR− subgroups are summarized in It has been suggested that ER/HER2 crosstalk may be implicated in the escape from HER2-directed therapy. Wang et al. described an increase of ER and its downstream products in 80% of ER+/HER2+ cell lines after a treatment with trastuzumab and lapatinib. Moreover, acquisition of resistance after trastuzumab and lapatinib could require the activation of the ER pathway via Bcl2 family members . P = 0.015) [P = 0.007) [HER2 overexpression leads to an activation of multiple signaling pathways including the PI3K/Akt pathway that result in the modification of cell growth, differentiation, and survival. In a recent study of Dave et al, after neoadjuvant trastuzumab 18.2% (4/22) of patients with low expression of PTEN (IHC) or PI3K mutations achieved pCR whereas 66.7% (6/9) of patients without low PTEN or PI3K mutations achieved pCR (= 0.015) . These f= 0.015)  who used= 0.015) . With la= 0.015) . PI3K mu= 0.007) . Hence, These results are discussed in other studies: in a retrospective study of 129 patients with HER2+ tumors including 26 cases treated with neoadjuvant trastuzumab and 48 metastatic breast cancer receiving a combination of taxane and trastuzumab, any relationship was found between PTEN loss and/or PI3K mutations and response to trastuzumab . A lowerAnother potential mechanism of resistance to trastuzumab is the accumulation of truncated forms of the HER2 receptor that lack the extracellular trastuzumab-binding domain. Amino terminally truncated carboxyl terminal fragments of HER2, collectively known as p95HER2, are frequently found in HER2+ breast cancer cell lines and tumors . The truP = 0.009). The resistance rate in the p95-positive group was 25.8% versus 48.7% in the p95-negative group (P = 0.014) [In preclinical models and in 46 metastatic patients treated with trastuzumab, the expression of p95HER2 was correlated with the lack of response to trastuzumab . Loibl e= 0.014) . Results= 0.014) .In the CHER-LOB trial the expression of p95HER2 was determined by immunohistochemical assay and was found to be present in 30.7% of cases. However, pCR rates were not different for p95HER2-positive and p95HER2-negative tumors in any treatment group . P = 0.045) and a decrease of sHER2 levels during neoadjuvant therapy (P = 0.02) which was also significant in multivariate analysis  [P = 0.043) [P = 0.031) [The extracellular domain of the HER2 protein can be cleaved from the surface by metalloproteases and detected in the peripheral blood as serum HER2 (sHER2). The remaining cleaved receptor is constitutively activated, suggesting that the presence of sHER2 also reflects a biological process leading to a more aggressive tumor behavior . Trastuz= 0.049) . In 210 = 0.043) . Moreove= 0.031) .Nonetheless, the biological relevance of elevated sHER2 is still unknown and other studies have reported a limited predictive utility of baseline sHER2 .P = 0.0359) [Before neoadjuvant chemotherapy with trastuzumab, circulating miR-210 levels were significantly higher in 11 patients who had residual disease than in 18 patients who achieved a pCR ( 0.0359) . γ receptor (FcγR) polymorphism has an effect on ADCC, which is one of the mechanisms of action of the trastuzumab. Tamura et al. observed in the tumors of 15 patients that the FfγR2A-131 H/H polymorphism predicts the pathological response to trastuzumab-based neoadjuvant chemotherapy in early-stage breast cancer [Some data suggested that the fragment C t cancer .Esteva et al. suggested that in 45 patients with HER2+ tumors who received concomitant trastuzumab and paclitaxel followed by FEC, a lower expression of genes involved with CD40 signaling was associated with a greater risk of residual disease .In the NOAH trial, in 171 patients with available biopsies, negative progesterone receptor and c-Myc amplification were associated with higher pCR rates after addition of trastuzumab compared to chemotherapy alone. Overexpression of membranous IGF1R was associated with higher likelihood of residual disease after trastuzumab-based chemotherapy .In the exploratory study presented by Holmes et al. at the 2011 ASCO meeting, 100 patients with stage II/III HER2+ breast cancer were randomized to trastuzumab, lapatinib, or trastuzumab plus lapatinib . Before P < 0.03). To identify an optimal threshold for the prediction of the pathological response, receiver operating characteristics (ROC) analysis gave an optimal cut-off value of −70% for ΔSUV. At this cut-off value, ΔSUV had a sensitivity of 89% while the specificity was 87%. From these results, an SUV decrease greater than 70% allowed for the early identification of the highly responsive tumors, which will be completely eradicated by trastuzumab-based neoadjuvant therapy, with an accuracy of 76% [In HER2-negative and HER2-positive tumors, the standard uptake value (SUV) decrease, studied with positron emission tomography (PET), is a strong predictor of pCR after only one course of chemotherapy . Other sy of 76% . These dy of 76% . This stTrastuzumab (Herceptin) has been a breakthrough in the treatment of HER2-positive breast cancer. Trastuzumab combined with chemotherapy has improved response rates, pathological complete response, progression free survival and survival in the neoadjuvant setting of these cancers. With the emergence of new anti HER2 therapies like lapatinib (Tyverb), pertuzumab (Tarjeta) and TDM1 (Kacyla), dual HER2 blockade, still associated with chemotherapy, has proven to be superior. In order to better individualize targeted therapies in specific tumor subgroups, additional knowledge is necessary. Different biomarkers have been studied to predict the response to anti-HER2 neoadjuvant therapies but until now, except the HER2 positivity, none has been validated. PET oriented strategy could be used to separate the most responsive tumors from the less responsive ones. Further studies are necessary to define robust, reliable, and reproducible biomarkers.


Human epidermal growth factor receptor 2 (HER2) is overexpressed in around 20–30% of breast cancer tumors. It is associated with a more aggressive disease, higher recurrence rate, and increased mortality. Trastuzumab is a HER2 receptor blocker that has become the standard of care for the treatment of HER2 positive breast cancer. The effectiveness of Trastuzumab has been well validated in research as well as in clinical practice. The addition of Trastuzumab to standard of care chemotherapy in clinical trials has been shown to improve outcomes for early stage as well as metastatic HER2 positive breast cancer. The most clinically significant side effect of Trastuzumab is the risk of cardiac myocyte injury, leading to the development of congestive heart failure. The emergence of patterns of resistance to Trastuzumab has led to the discovery of new monoclonal antibodies and other targeted agents aimed at overcoming Trastuzumab resistance and improving survival in patients diagnosed with HER2 positive breast cancers. Human epidermal growth factor receptor HER2 overexpression is present in approximately 20–30% of breast cancer tumors. HER2 overexpression is associated with a more aggressive disease, higher recurrence rate, and shortened survival –4. TrastHER2 is part of the epidermal growth factor (EGF) family, along with 3 other receptors: epidermal growth factor receptor , HER2 (erbB2), HER3 (erbB3), and HER4 (erbB4). The HER2 gene is located on the long arm of chromosome 17 and encodes a 185-kDa transmembrane protein . The HERThe mechanism of action of Trastuzumab is perceived to be through both innate and adaptive immunities. Innate mechanisms lead to cell cycle arrest, with a noted increase in p27 levels, and decrease in cyclin D1 and cyclin-dependent kinase 2 activity . TrastuzTrastuzumab has become the standard of care in the treatment of patient with HER2 positive breast cancer. Data from several randomized trials demonstrated that the addition of Trastuzumab to chemotherapy regimens in the adjuvant setting improves outcome in women with early stage breast cancer –22. In tThe ideal timing of Trastuzumab administration appears to be concurrent administration with chemotherapy, based on the NSABP trial . HoweverTrastuzumab has also been shown to be effective in improving outcome for patients with HER2 positive metastatic breast cancer . This efTrastuzumab has been evaluated in combination with hormonal therapy in postmenopausal women with metastatic breast cancer, that is, both hormone receptor and HER2-positive. The TAnDEM study showed that the combination of anastrozole and Trastuzumab was more effective in improving outcomes when compared with anastrozole alone .Trastuzumab has been evaluated extensively in the neoadjuvant setting. A review by Lazaridis et al. presented positive data regarding the integration of Trastuzumab into neoadjuvant treatment regimens . The folLastly, a trial by Buzdar et al. evaluated the effect of adding Trastuzumab to chemotherapy in the neoadjuvant setting for operable HER2 positive breast cancer. The trial was stopped early due to significantly higher rates of pathological response in the Trastuzumab arm . PatholoCardiac toxicity in patients receiving anthracycline-based chemotherapy has been well established. The mechanism of doxorubicin cardiotoxicity involves direct injury to cardiac myocytes through increased free radicals and oxidative stress –45. DoxoTrastuzumab therapy, unlike anthracyclines, has been associated with reversible injury to the cardiac myocytes. This is mainly due to the fact that it does not appear to cause structural damage to the myocardium . Human eHER2 binds to Neuregulin-1 and initiates this cascade, perpetuating signals to maintain cell survival, response to stress, and prevent apoptosis. Trastuzumab blocks the HER2 receptor, causing these pathways to be interrupted –56. The Certain risk factors have been associated with increased risk of cardiac dysfunction with Trastuzumab treatment. These included age >50 years, concomitant use of an anthracycline, hypertension requiring treatment, and post-AC LVEF values of 50–54% . In addiTrastuzumab has become widely used for the treatment of HER2 positive breast cancer. Despite the success of Trastuzumab-based therapy in treating all stages of HER2-positive breast cancer, resistance to Trastuzumab is an important issue which affects outcome for a subset of patients. These observations have prompted research into the mechanisms of Trastuzumab resistance, which are thought to underlie failure of therapy . No cleaLapatinib is a dual EGFR and HER2 receptor tyrosine kinase inhibitor , 76. LapTrastuzumab has been proven to be effective in improving outcomes for patients with early operable as well as metastatic HER2 positive metastatic breast cancer. It has also been shown to increase the pathological response when used in the neoadjuvant setting. Trastuzumab therapy has been associated with an increased risk of cardiac toxicity, especially when used in combination with anthracyclines. Resistance to Trastuzumab therapy has also been documented, as patients have had disease progression while on treatment. A better understanding of the mechanisms of resistance to Trastuzumab therapy constitutes the cornerstone of finding new better tailored therapeutic agents capable of reducing rates of treatment failure and disease progression. Multiple new drugs are under investigation, targeting a wide array of receptors and cell cycle regulatory proteins. Preclinical pharmacological and genomic data will soon make its way into the clinical domain. Integrating this knowledge into therapeutic decision making may change the identity of HER2 positive breast cancer from a one drug for all diseases into a personalized individualized therapy, tailored to each patient's predictable response.


HER2-positive breast cancers have poorer prognosis and are prime candidates for molecular-targeted therapy because they are driven by the unique mechanism of HER2 oncogene addiction. While anti-HER2 agents such as trastuzumab and lapatinib are integral to the treatment of HER2-positive breast cancer, intrinsic and secondary resistance pose a significant challenge, underscoring the need to develop novel anti-HER2 therapies. In recent years, an array of promising and novel anti-HER2 therapeutic agents and their combinations have entered various stages of clinical development. However, questions remain on the optimal sequences of HER2-directed therapies and selection of patients for the most appropriate drug or combinations; incompletely defined mechanisms of trastuzumab action and resistance have also dampened the progress of more successful biomarker-driven treatment approaches. This paper summarizes existing preclinical and clinical evidence on the mechanisms of trastuzumab action and resistance and provides an up-to-date overview of novel HER2-directed therapies in clinical development. Human-epidermal-growth-factor-receptor-2 (HER2-) overexpressing breast cancers account for 20–25% of invasive breast cancers and are associated with an aggressive biologic behaviour translating to poorer clinical outcomes . The dev Despite this notable success, 70% of patients with HER2-positive breast cancers demonstrate intrinsic or secondary resistance to trastuzumab , highlig The data for this paper were obtained by searching the PubMed database using Entrez. The search terms used included the following combined subject headings: HER2-positive breast cancer, herceptin, trastuzumab, resistance, p95HER2, phosphatidylinositol 3-kinase (PI3K)/Akt, phosphatase and tensin homolog (PTEN), HER3, insulin-like growth factor 1 receptor (IGF-1R), angiogenesis, lapatinib, pertuzumab, trastuzumab-DM1 (T-MD1), HER2 tyrosine kinase inhibitors (TKIs), heat-shock protein (HSP) 90 inhibitors, vascular endothelial growth factor (VEGF) inhibitors, IGF-1R inhibitors, and bispecific antibodies. The citation lists of all retrieved articles were examined to identify potentially relevant articles, and proceedings from conferences of the American Society of Clinical Oncology and San Antonio Breast Cancer Symposium were searched for relevant abstracts.HER2 belongs to a family of transmembrane receptor tyrosine kinases, which also includes HER1 ), HER3, and HER4. Ligand binding to the ECD of these receptors results in either homodimerisation between two molecules of the same receptor or heterodimerizaton between two different receptors. Dimerisation in turn induces tyrosine kinase phosphorylation and downstream signalling onto the PI3K and mitogen-activated protein (MAP) kinase cascades, leading to cell survival and proliferation, respectively. While EGFR, HER2, and HER3 are all implicated in carcinogenesis, the dimers vary in their signalling potencies, with the HER2/HER3 heterodimer possessing the strongest mitogenic potency, particularly in the activation of the PI3K/Akt survival pathway. The HER2 protein possesses two unique features; firstly, unlike other HER family members which exist in an inactivated state, it can be constitutively activated and is capable of ligand-independent dimerisation, and secondly, it is the preferred heterodimerisation partner for other HER proteins , 6. Ironically, the mode of action of trastuzumab remains incompletely defined despite its routinary clinical application. Extensive preclinical research has been conducted to elucidate these mechanisms, and the following possibilities have been proposed.γ receptor on immune effector cells, particularly natural-killer cells, resulting in cell lysis of HER2-positive target cells bound to trastuzumab [γ receptors [in vivo data from a pilot study of 11 patients with HER2-positive early breast cancer, where a positive correlation was observed between response to neoadjuvant trastuzumab and ADCC activity [An important proposed mechanism of action of trastuzumab is antibody-dependent cellular cytotoxicity (ADCC), which is triggered through the detection of Fc portion of trastuzumab by the Fcstuzumab . This meeceptors . These oactivity .p95HER2 fragments resulting from the proteolytic cleavage of the HER2 ECD have generated much interest due to the association of the 100–115 kDa p95HER2 fragment with a clinically more aggressive subset of HER2-positive breast cancers . A preclKip1 expression [The role of trastuzumab in abrogating the PI3K/Akt signaling pathway has been addressed in two preclinical studies, where treatment of HER2-gene-amplified breast cancer cells with trastuzumab caused growth inhibition through PTEN upregulation and downregulation of PI3K activity and Akt function , 13. Othpression , 15.β1, further enhances VEGF secretion [Investigators have reported that HER2-overexpressing cell lines possess higher basal levels of VEGF expression and that stimulation with the HER3 and HER4 ligand, heregulin ecretion , suggestecretion , whilst ecretion .Understanding the mechanisms behind trastuzumab resistance is a critical step towards the development of novel anti-HER2 strategies. Molecular mechanisms that contribute to trastuzumab resistance include the following.Truncated p95HER2 fragments exhibit resistance to trastuzumab because they lack trastuzumab-binding epitopes and may arise either through proteolytic cleavage of the HER2 ECD or alternative translation-initiation sites of the HER2 protein . Due to Genetic aberrations in the PI3K/Akt pathway are among the most prevalent in breast cancer and have been shown to mediate trastuzumab resistance. These include loss-of-function PTEN deletions and activating mutations of PI3KCA, the gene encoding the p110 catalytic subunit of PI3K . A preclInhibition of the HER2 oncogenic pathway with trastuzumab may result in compensatory crosstalk and activation of alternative signalling pathways, such as IGF1R and HER3 signalling pathways . AberranThe binding between trastuzumab and HER2 may be disrupted by the membrane-associated glycoprotein mucin-4 (MUC4), as evidenced by the overexpression of MUC4 in a trastuzumab-resistant breast cancer cell line and subsequent restoration of trastuzumab binding through MUC4 siRNA knockdown . SimilarOnly two agents possess regulatory approval for the treatment of HER2-positive breast cancer, with a lull of nearly a decade between the initial FDA approval of trastuzumab and that of lapatinib in 2007. Therefore, the management of patients with prior trastuzumab failure has long represented an area of unmet clinical need, with existing treatment options that include HER2-directed therapies being limited to (i) the continuation of trastuzumab beyond progression, (ii) the alternative use of lapatinib, or (iii) a combination of both.versus 27%, P = 0.0115) and median time-to-progression  [NCT00444587; THOR, NCT00448279) [Preclinical data showing that trastuzumab withdrawal resulted in rapid re-growth of trastuzumab-resistant cell lines , 31 lent 0.0338) . Data fr0448279) .Lapatinib is a reversible small-molecule TKI of EGFR and HER2 which was first found to possess antitumour activity in HER2-dependent cells lines . Subsequversus 14%, P < 0.09) and PFS  in this group of patients [Lapatinib gained regulatory approval for use in HER2-positive metastatic breast cancer patients who have received prior anthracyclines, taxanes, and trastuzumab, based on a pivotal phase III study demonstrating the superiority of lapatinib and capecitabine compared to capecitabine alone in ORR . In addition, a randomised phase II study has been planned to evaluate the efficacy of lapatinib versus trastuzumab in combination with first-line chemotherapy in metastatic patients whose tumours display concomitant overexpression of HER2 and p95HER2 (NCT01137994). Lapatinib is also being evaluated as monotherapy or in combination with trastuzumab in early-stage breast cancer in the adjuvant  and neoadjuvant  settings. Lapatinib is currently being evaluated in combination with chemotherapy as first-line metastatic treatment in HER2-positive disease in the ongoing MA31 study, where it is being compared to trastuzumab in combination with taxane-based chemotherapy  and median PFS  compared to lapatinib alone [versus 29.5% versus 24.7%, respectively; P < 0.01); dual blockade was associated with mildly increased but manageable toxicities [A preclinical study in HER2-overexpressing breast cancer cell lines suggested that dual anti-HER2 blockade was synergistic because lapatinib induced HER2 accumulation at the cell surface, resulting in enhanced trastuzumab-binding and increased trastuzumab-mediated ADCC . A randoib alone . These fxicities .The emergence of more robust preclinical data in recent years has catapulted therapeutic advances in this arena, resulting in a rapid expansion in the armamentarium of anti-HER2 agents being developed clinically. These include dimerisation inhibitors, antibody-drug conjugates, tyrosine kinase inhibitors, HSP90 inhibitors, mTOR/PI3K inhibitors, antiangiogenic agents, IGF-1R inhibitors, and bispecific antibodies.One of the closest to regulatory approval amongst several novel anti-HER2 agents in advanced clinical development is pertuzumab, which is a humanised monoclonal antibody that binds to an epitope on the dimerisation domain located on domain II of the HER2 ECD, distinct from the binding site of trastuzumab on domain IV. Consequently, it potently inhibits HER2 as well as the dimerisation of HER2 with other HER family receptors, including HER3 . The groNCT00567190) evaluated the benefit of adding pertuzumab to the combination of trastuzumab and docetaxel in previously untreated HER2-positive metastatic breast cancer. Although no comprehensive data has been released, preliminary results of the recently completed study indicate that the primary endpoint of PFS was significantly prolonged in the experimental pertuzumab-containing arm. These potentially practice-changing findings have led Genentech/Hoffman-La Roche to seek regulatory approval for the drug combination [NCT01358877). Pertuzumab combined with trastuzumab results in concurrent blockade of multiple HER family members, and their synergistic activity has been demonstrated in HER2-overexpressing breast cancer xenograft models . Dual inbination . A similversus 29% versus 24%, P < 0.014). Interestingly, a promising pCR rate of 17.8% was achieved with dual anti-HER2 blockade in the absence of chemotherapy, further highlighting the potential of combining two anti-HER2 agents with different mechanisms of action [ The dual anti-HER2 combination of pertuzumab and trastuzumab has been evaluated without chemotherapy in the open-label, phase II BO17929 study conducted on HER2-positive metastatic breast cancer patients with prior trastuzumab failure, yielding extremely promising results. Complete response rates, ORR, and CBR were 7.6%, 24.2%, and 50%, respectively, and the median PFS was 5.5 months. The combination was well tolerated, and importantly, the incidence of cardiac dysfunction was minimal . The ratf action .T-DM1 is the first and only HER2-directed ADC in clinical development and combines the intracellular delivery of a microtubule-depolymerisation agent, DM1, a maytansine derivative, with the antitumour activity of trastuzumab. Upon binding to the HER2 receptor, T-DM1 is internalised and DM1 released intracellularly, enabling the selective delivery of the potent cytotoxic agent to HER2-overexpressing cells with limited systemic toxicity , 49. PreExcellent response rates of 40% to T-DM1 have been reported in an open-label, single-arm, phase II study conducted in patients with HER2-positive metastatic breast cancer, all of whom had progressed on trastuzumab-based therapy and 40% of whom had received prior lapatinib therapy. Severe toxicities including grade 4 thrombocytopenia and transaminitis were rare at 6% . The higversus 41%; T-DM1 versus TH, resp.), T-DM1 was much less toxic, with grade 3 and above toxicities approximately half that of TH (37.3% versus 75%) [NCT00829166). In addition, the role of T-DM1 delivered sequentially with anthracycline-based chemotherapy is being explored in the adjuvant/neoadjuvant setting in patients with HER2-positive early breast cancer (NCT01196052).Multiple clinical trials have been designed to compare the efficacy of single-agent T-DM1 with existing HER2-directed therapies combined with chemotherapy in patients with HER2-positive metastatic breast cancer. Preliminary results of a randomised phase II study (TDM4450g) of T-DM1 versus trastuzumab plus docetaxel (TH) in the first-line treatment of HER2-positive metastatic breast cancer patients were recently released. While response rates were comparable in the two arms (48% sus 75%) . The EMINCT01120184) is underway to evaluate T-DM1 alone and T-DM1 combined with pertuzumab versus the reference arm of trastuzumab plus taxane in previously untreated patients with HER2-positive metastatic breast cancer. Based on preclinical research demonstrating the synergistic antitumour activity of T-DM1 and pertuzumab in a trastuzumab-resistant breast cancer xenograft model , a phaseSince trastuzumab resistance may arise from cross-talk among other HER proteins resulting in lateral activation and incomplete inhibition of downstream signalling, one approach to overcoming trastuzumab resistance is the simultaneous inhibition of multiple HER receptors . SeveralNeratinib, a potent, low-molecular-weight, orally administered, irreversible pan-HER  receptor TKI, is one of the most advanced novel HER TKI in clinical development and offers more complete HER receptor blockade than lapatinib which inhibits only HER1 and HER2. An early preclinical study demonstrated that the compound inhibited cell proliferation of HER2-overexpressing breast cancer cell lines and xenografts through downregulation of the MAP kinase and PI3K/Akt pathways and induced cell cycle arrest .NCT00777101) and in combination with chemotherapy in a randomised phase II study  comparing neratinib and paclitaxel versus trastuzumab and paclitaxel in previously untreated metastatic disease. It is also being evaluated in early-stage disease both in the neoadjuvant and adjuvant settings (NCT01008150 and NCT00878709). Clinical studies have evaluated neratinib as a single agent or in combination with trastuzumab or chemotherapy. A recently published phase II, open-label study evaluated the efficacy and tolerability of neratinib monotherapy in two cohorts of patients with HER2-positive metastatic breast cancer: those with and those without prior trastuzumab treatment. The efficacy results of the two cohorts were a 16-week PFS (the primary endpoint) of 59% and 78%, respectively, and an ORR of 24% and 56%, respectively, while diarrhoea was a common but manageable toxicity . DespitePreliminary data from a phase I/II study of the combination of neratinib and trastuzumab in HER2-positive metastatic breast cancer patients with prior trastuzumab exposure demonstrated both tolerability and efficacy, with an ORR of 27%, 16-week PFS of 47%, and median PFS of 19 weeks . These dNCT01125566).While afatinib (BIBW-2992) targets the same receptors as lapatinib, it does so in an irreversible manner, resulting in more sustained inhibition of EGFR and HER2. It has demonstrated activity in trastuzumab-resistant HER2-overexpressing cell lines as well as promising clinical activity in phase I development . Its potNCT00650572) [NCT00710736).Two other orally active TKIs, ARRY-380 and ARRY-334543, are in the process of development by Array BioPharma. ARRY-380 is a reversible and selective HER2 TKI which has demonstrated significant dose-related tumour growth inhibition superior to that of trastuzumab and lapatinib in preclinical studies, as well as promising efficacy in an ongoing phase I expansion study in HER2-overexpressing solid tumours, including activity in p95HER2-overexpressing tumours (0650572) . ARRY-330650572) , is currHSP90 belongs to a family of chaperone proteins which facilitate the conformational maturation and folding of various signalling proteins, including HER2. In a preclinical study, interference with its function led to ubiquitylation and proteasomal degradation of HER2 and the resultant abrogation of the PI3K/Akt pathway, in turn causing growth inhibition of HER2-overexpressing tumours in murine xenograft models . A potenNCT01271920).  At least three HSP90 inhibitors have undergone clinical investigation in HER2-positive breast cancer, and to date, all have been evaluated in combination with trastuzumab. One promising compound is tanespimycin (17-AAG/KOS-953), which has demonstrated significant activity and tolerability in combination with trastuzumab in a phase II study conducted in advanced trastuzumab-refractory HER2-positive breast cancer, with an ORR of 24%, CBR of 59%, median PFS of 6 months, and median OS of 17 months . These dPTEN loss leads to the constitutive activation of Akt, which in turn activates mTOR in the PI3K/Akt signalling pathway. Two preclinical studies suggest the potential of this pathway as a therapeutic target; HER2-overexpressing breast cancer cell lines and xenograft models transfected with loss-of-function PTEN mutations and activating PIK3CA mutations resulted in trastuzumab and lapatinib resistance which was effectively reversed by the PI3K/mTOR inhibitor, NVP-BEZ235 , 69.NCT01283789).Everolimus is the most advanced mTOR inhibitor undergoing clinical investigation and is being developed in combination with existing HER2-directed therapies with or without chemotherapy. A recently published phase I/II study evaluated the chemotherapy-free combination of everolimus and trastuzumab in heavily pretreated HER2-positive metastatic breast cancer patients with prior trastuzumab exposure, which yielded an ORR of 15%, CBR of 34%, and median PFS of 4.1 months. The overall safety profile was acceptable, but did include a less than 10% incidence of grade 3 diarrhoea, fatigue, and stomatitis . The comNCT00876395, NCT01007942).The combination of everolimus with trastuzumab and weekly paclitaxel appeared highly active in heavily pre-treated HER2-positive metastatic breast cancer patients with prior trastuzumab and taxane exposure, yielding an ORR of 25%, stable disease (SD) rate of 56%, and acceptable toxicity profile in a multicentre phase II study . Two plaNCT01111825).Apart from everolimus, two other rapamycin analogues in the developmental pipeline in the treatment of HER2-positive breast cancers are deforolimus (AP23573) and temsirolimus (CCI-779). A phase II study of oral deforolimus in combination with trastuzumab has recently been completed in HER2-overexpressing metastatic breast cancer patients with prior trastuzumab exposure (NCT00736970). Compensatory increase in HER3 signalling with inhibition of the PI3K/Akt signalling pathway supports the novel approach of dual inhibition with an mTOR inhibitor and a pan-HER receptor TKI , and theNCT01132664), while BEZ235, a dual PI3K and mTOR inhibitor, is planned for evaluation as a single-agent in a phase II study (NCT01288092) [Novartis is currently conducting early-phase studies of two PI3K inhibitors that compete reversibly with the ATP-binding site of the PI3K p110 catalytic subunit. BKM120, a pan-class I PI3K inhibitor, is being assessed in combination with trastuzumab in a phase Ib/II study of HER2-overexpressing breast cancer patients with prior trastuzumab exposure (1288092) , 74.NCT00391092) and ECOG1105 (NCT00520975). The same strategy is also being evaluated in the adjuvant setting in the ongoing BETH study (NCT00625898) [The rationale for the simultaneous blockade of both HER2 and VEGF pathways is based on preclinical data demonstrating upregulation of angiogenesis in HER2-overexpressing breast tumours, and clinical data demonstrating that overexpression of both HER2 and VEGF was associated with a poorer prognosis in breast cancer patients in a large retrospective analysis . Followi0625898) .NCT00558103). A phase II open-label study assessed the safety and efficacy of adding pazopanib, an oral angiogenesis inhibitor targeting VEGFR, platelet-derived growth factor receptor and c-kit, to lapatinib in previously untreated HER2-positive metastatic breast cancer. Results showed lower 12-week progressive disease (19% versus 27%) and better response rates (44% versus 30%) with the combination compared to lapatinib alone, and whilst toxicities of diarrhoea and abnormal liver function tests were greater in the combination arm, they were still regarded as tolerable . This haPfizer) and small-molecule selective IGF-1R TKI, NVP-AEW541 (Novartis) have demonstrated antitumour activity against trastuzumab-resistant breast cancer tumour models [NCT0068493), whilst the combination of trastuzumab and BMS-754807, a small-molecule, reversible IGF-1R TKI, is undergoing evaluation in patients with prior trastuzumab failure in a phase I/II study (NCT00788333).Bidirectional cross-talk between the IGF-1R and HER2 signalling pathways is one mechanism of trastuzumab resistance, and the human anti-IGF-1R antibody, CP-751871  [NCT00452140). Continuing strategies to overcome trastuzumab resistance include the development of a class of agents known as trifunctional, bispecific antibodies. MM-111 is an antibody targeting both the HER2/HER3 heterodimer and the HER3 ligand, heregulin, and is currently being evaluated in combination with trastuzumab in HER2-overexpressing metastatic breast cancer patients with prior trastuzumab exposure (1097460) . A phaseNCT00301899) and NeoSphere [Rational combinations of novel anti-HER2 therapies are of particular interest not only because of their ability to overcome trastuzumab resistance through their concurrent blockade of multiple HER2 family members, but also for their potential to offer chemotherapy-free therapeutic options that are relatively less toxic. The combination of trastuzumab and lapatinib has recently been integrated into clinical practice . Most oteoSphere , which seoSphere . All theeoSphere . Lastly,eoSphere . Apart fWith the emergence of several novel HER2-directed agents, recent therapeutic advancements have been remarkable compared to the limited progress following the initial regulatory approval of trastuzumab more than a decade ago. Improved insights into the mechanisms of trastuzumab resistance have led to new treatment strategies employing dual anti-HER2 blockade, which have improved response rates and progression-free survival.While the substantial amount of research dedicated to the development of novel ant-HER2 agents is laudable, the vast array of treatment options in an ever-changing landscape of anti-HER2 therapy may raise more questions than answers. Clinicians will be continually challenged to design optimal combinations and sequences of anti-HER2 agents, chemotherapeutic agents, and even endocrine therapy for the individualised treatment of patients with HER2-positive breast cancer. These issues can rarely be fully addressed through the simplistic design of current therapeutic trials. At present, a physician treating an individual who has progressed on first-line trastuzumab-based therapy already faces the dilemma of whether the patient should receive further trastuzumab together with an alternative chemotherapeutic agent, continue trastuzumab in combination with lapatinib, or switch to lapatinib. The growing number of HER2-directed therapies in the pipeline will only add to the complexity of this decision-making process. In addition, a large proportion of HER2-positive patients relapsing with metastatic disease in the future will have received adjuvant trastuzumab or even lapatinib therapy, indicating that new treatment paradigms will be required for this group of patients.The extensive preclinical efforts in elucidating mechanisms of trastuzumab resistance should translate into individualised therapy through biomarker-driven approaches. However, this would first require the development of validated assays for the accurate measurement of resistance factors in archival tissue specimens, and to date, advancements in this arena have been slow . For exaTrastuzumab resistance poses a significant challenge in the treatment of HER2-positive breast cancer. Substantial research has been dedicated to elucidating mechanisms of trastuzumab resistance, as well as developing a myriad of novel anti-HER2 therapeutic agents with promising clinical activity. This has resulted in a major paradigm shift in the treatment of HER2-positive breast cancer and has given rise to a rapidly expanding range of therapeutic options in active clinical development. Future efforts should be directed towards biomarker-driven, HER2-directed therapies for optimal selection of therapy for the individual patient.


Trastuzumab has recently been introduced as a treatment for HER2-positive metastatic and/or unresectable gastric cancer (MUGC); however, compared with breast cancer, some issues concerning HER2 and trastuzumab therapy for gastric cancer remain unclear. A 74-year-old woman received trastuzumab-containing chemotherapy for HER2-positive MUGC. She had a marked response to 8 months of chemotherapy, and gastrectomy and hepatic metastasectomy with curative intent were performed. The resected specimen showed complete loss of HER2 positivity in the residual tumor. For MUGC, a change in HER2 status during the course of the disease with or without chemotherapy has rarely been reported. However, in breast cancer, a significant frequency of change in HER2 status during the course of disease has been reported, and reevaluation of HER2 positivity in metastatic/recurrent sites is recommended. The choice of trastuzumab for MUGC is currently based on the HER2 status of the primary tumor at the time of initial diagnosis, without reassessment of HER2 status during the course of disease and/or in metastatic/recurrent sites, on the assumption that HER2 status is stable. However, our case casts doubt on the stability of HER2 in gastric cancer. The primary treatment for patients with metastatic and/or unresectable gastric cancer (MUGC) is systematic chemotherapy. Although the combination of 5-fluorouracil and cisplatin has been the standard regimen for the treatment of MUGC, new cytotoxic agents such as S-1, capecitabine, paclitaxel, docetaxel, oxaliplatin, irinotecan, and their combinations have proven to be more effective and better tolerated, resulting in the improvement of median survival up to 13 months .We report a case in which chemotherapy containing trastuzumab made it possible to perform curative gastrectomy in a patient with HER2-positive MUGC at initial diagnosis; this case is noteworthy in that HER2 positivity in resected specimens of the residual tumor was completely lost. Loss of HER2 positivity after treatment with trastuzumab for HER2-positive MUGC has rarely been reported. HER2 status is an essential biomarker for the effectiveness of trastuzumab, and consequently, knowledge of HER2 stability during the course of disease is critical for determining the introduction, the continued use, or elimination of trastuzumab. We discuss the stability of HER2 status in gastric cancer and provide a literature review of this important topic.A 74-year-old woman with the chief complaint of palpable masses in her abdomen presented to our hospital in May 2013. Physical examination revealed one 50-mm mass in the upper central abdomen and three 20–30-mm palpable masses in the other parts of her abdomen. Esophagogastroduodenoscopy (EGD) revealed an ulcerative mass with raised margins along the lesser curvature extending from the lower body of the stomach to the antrum . Biopsy 2/day) orally on days 1–14, cisplatin (80 mg/m2) intravenously on day 1, and trastuzumab (8 mg/kg loading dose followed by 6 mg/kg) intravenously on day 1. From the 3rd course, the doses of capecitabine and cisplatin were reduced to 1500 mg/m2/day and 60 mg/m2, respectively, due to nonhematologic toxicity . After completion of the 4th course of chemotherapy, at 3 months after diagnosis, a 76% decrease in measureable tumor burden compared to baseline according to RECIST 1.1 criteria was observed. From the 6th course, cisplatin was discontinued due to renal impairment, but treatment with capecitabine and trastuzumab continued. After completion of the 11th course, at 8 months after diagnosis, EGD showed a marked reduction of the gastric tumor  according to the 7th TNM classification of the American Joint Committee on Cancer/Union for International Cancer Control (AJCC/UICC) staging system for gastric cancer. She was treated with 3-week courses of capecitabine (2000 mg/mic tumor , and conic tumor  showed aic tumor . AscitesGiven this response to the treatment, complete resection of the residual tumor was deemed possible, and 9 months after the diagnosis, distal gastrectomy with D2 lymphadenectomy and hepatic metastasectomy of the small nodule in the lateral segment were performed. Operative findings showed no macroscopic peritoneal metastasis and the absence of peritoneal lavage cytology. Macroscopic complete resection was possible. Pathologic findings of the 36 × 25 mm mass from the resected stomach revealed a moderately differentiated adenocarcinoma with subserosal invasion  and hyalApproximately 15–20% of invasive breast cancers have HER2 overexpression and/or gene amplification . HER2 haIn breast cancer, discordance in HER2 status between the primary tumor and the metastasis/recurrence and HER2 stability during the course of disease has been evaluated in several reports. The discordance rate of HER2 status in breast cancer has been reported to be 3–16% –13, withSeveral previous reports have evaluated how chemotherapy with or without anti-HER2 agents, including trastuzumab, influences HER2 expression. The discordance rate of HER2 status before and after NAC has been reported to be 0–9.5% –17. In HIn addition to studying the association between HER2 status and traditional chemotherapeutic agents, several reports have analyzed the association between change in HER2 status and trastuzumab therapy. A loss of HER2 positivity in patients treated with trastuzumab therapy has been reported in 14.7–37% of HER2-positive breast cancers –21. NakaHER2 overexpression and/or amplification occurs in 7–34% of gastric cancer cases , 23. In When analyzing loss of HER2 in a sample obtained after treatment, we must consider the possibility of a false-negative result for HER2 expression on immunohistochemistry. A sample taken by biopsy is only part of a tumor, and a resected sample might be one of many tumors within the body; therefore, loss of HER2 might be a false-negative due to heterogeneity within the tumor or discordance between the sites of tumors. In fact, it is known that the heterogeneity of HER2 expression within gastric tumors is much more frequent than in breast cancer , 23. TheCurrent practice guideline for the treatment of breast cancer recommended that biomarkers, including HER2 status and hormone receptors, should be evaluated not only for the primary tumor but also for the initial metastatic or recurrence tumor tissues, especially if the first determination of HER2 status is negative, in order not to lose the chance of anti-HER2 therapy . CurrentAlthough the use of trastuzumab has been shown to be highly effective in treating HER2-positive MUCG, several issues regarding HER2 stability and trastuzumab therapy for gastric cancer remain to be elucidated. First, clinicians need to know how often HER2 status converts with tumor progression, metastasis, or treatment. If a change in HER2 status is found to be significantly frequent in gastric cancer, management strategy recommendations similar to those of breast cancer should be introduced for gastric cancer, although it will be important to consider that biopsy from metastases/recurrence or metastasectomy is invasive and burdensome for patients. If the factors that contribute to HER2 change are identified, only those patients who have such factors, rather than all patients with MUGC, would need to submit to biopsy from metastases/recurrence or metastasectomy. Second, clinicians need to evaluate whether loss of HER2 positivity in specimens obtained during the disease course in HER2-positive gastric cancer always indicates resistance to trastuzumab. As we have mentioned, HER2 status taken from samples may not always represent all tumors in the body. In the present case, although macroscopic complete resection was possible, there was still a sufficient possibility of remaining micrometastases. We decided to treat the patient with adjuvant therapy comprised of capecitabine and trastuzumab after the patient gave her informed consent. Therapy comprised of capecitabine and trastuzumab was chosen because her tumors were not resistant to these medications until resection, and trastuzumab has a significant benefit in tumor cell eradication in the event that the remaining micrometastases retain HER2-positivity. Third, clinicians need to know if the loss of HER2 positivity has a significant prognostic impact on MUGC, because some studies have shown that loss of HER2 positivity in HER2-positive breast cancer was associated with a significantly worse prognosis compared to patients with tumors that maintained HER2 expression , 20, 21.Even if a marked response to chemotherapy allows the possibility of curative resection in MUGC, currently, the consistent standard treatment is to continue chemotherapy. However, the survival rate in MUGC treated by chemotherapy alone is obviously insufficient. Surgical resection with curative intent after a response to chemotherapy for MUGC is called adjuvant or salvage surgery. The benefit of such surgery was recently evaluated, and a favorable prognosis was suggested, with a 3-year survival rate of 46–55% and a median survival of 29–43 months –32, althIn conclusion, we report the case of a patient with HER2-positive MUGC at initial diagnosis who received chemotherapy including trastuzumab; following chemotherapy and surgery in this patient, a resected specimen of the stomach showed loss of HER2-positivity in the residual tumor, suggesting that HER2 status is not always stable. Treatment with trastuzumab is very effective and less toxic than traditional cytotoxic drugs. If HER2 positivity is gained during the course of disease, it is an easy judgment for clinicians to add trastuzumab to chemotherapy, thus allowing patients to benefit from trastuzumab therapy. However, when cases convert from positive HER2 status to negative HER2 status, clinicians remain uncertain as to whether the change in status is truly due to a biologic change rather than a false-negative result. Therefore, it is a more difficult and less confident judgment to remove trastuzumab from chemotherapy, even though its removal may result in avoiding unnecessary treatment. Further studies concerning HER2 status in gastric cancer are needed in order to appropriately use trastuzumab for these patients.