the ms raw files were processed with spectronaut 17, direct dia +, using a full - length homo sapiens database ( uniprot, january 2022 ) and common contaminants, such as trypsin and keratins, as reference. data analysis was performed using perseus 2. 0. 9. 0. values below 5 after log2 transformation ( result of matching across runs in spectronaut 17 ) were transformed to nonvalid values. to determine significant differences in protein abundance, each condition was first compared to the control by standard t - test. only proteins that were significantly more or less abundant in minimal one condition were further analyzed. missing values were replaced by normally distributed random values. width and down shift were used separately for each column according to default settings. after grouping replicates, significant changes were determined using a permutation - based false discovery rate ( fdr ≤ 0. 05 ). hallmarks of cancer and wikipathways were downloaded from the molecular signature database ( msigdb ) website ( https: / / www. gsea - msigdb. org / gsea / msigdb / ). gseapy ( https: / / gseapy. readthedocs. io / en / latest / introduction. html ) was used to quantify the enrichment of pathways in transcriptomic and proteomic data, using a ranked gene list based on log2fc as input, with a minimum gene set size of 5, maximum size of 1, 000 and 500 permutations. pathways that were significant at fdr p < 0. 1 were reported. no statistical method was used to predetermine sample size. sample sizes were determined on the basis of previous studies by us and others using similar technologies and approaches. for mouse experiments, the number was chosen to comply with 3r principles. no animals or data points were excluded from the analyses. randomization was used for animal experiments and mice were blindly selected before injection. all statistical data are based on biological replicates. statistical analysis was performed with prism software, version 9 for mac os x or windows ( graphpad software ). all experiments were performed at least twice with similar results. an unpaired two - sided student ’ s t - test was used for the comparison of two groups, assuming a normal distribution, which was, however, not formally tested. a mann – whitney u - test was used for data that were not normally distributed. for comparisons involving more than two groups, we used a two - sided one - way or two - way analysis of variance ( anova ) with bonferroni post hoc multiple comparison test. further information on research design is available in the nature portfol io reporting summary linked to this article. the fact that the mediterranean diet could represent a source of natural compounds with cancer - preventive and therapeutic activity has been the object of great interest, especially with regard to the mechanisms of action of polyphenols found in olive oil and olive leaves. secoiridoid oleuropein ( ole ) and its derivative hydroxytyrosol ( 3, 4 - dihydrox yphenylethanol, ht ) have demonstrated anti - proliferative properties against a variety of tumors and hematological malignancies both in vivo and in vitro, with measurable effects on cellular redox status, metabolism, and transcriptional activity. with this review, we aim to summarize the most up-to-date information on the potential use of ole and ht for cancer treatment, making important considerations about ole and ht bioavailability, ole - and ht - mediated effects on drug metabolism, and ole and ht dual activity as both pro - and antioxidants, likely hampering their use in clinical routine. also, we focus on the details available on the effects of nu trit ionally relevant concentrations of ole and ht on cell viability, redox homeostasis, and inflammation in order to evaluate if both compounds could be considered cancer - preventive agents or new potential chemotherap y drugs whenever their only source is represented by diet. cancer insurgence and progression are complex processes, depending on the combination of unmodifiable genetic and modifiable environmental / lifestyle - related factors. with this premise, it sounds perfectly understandable that scientific evidence has corroborated the role of a healthy diet and dietary intervention as potentially beneficial approaches contributing to cancer prevention. epidemiological and experimental evidence has confirmed that the so - called mediterranean diet is a source of molecules that may mitigate cancer risk factors like chronic inflammation and redox imbalance, thus participating in the prevention of carcinogenesis in terms of loss of cell cycle regulation and proper immune modulation, as well as in the inhibition of angiogenesis and metastasis. moreover, some of these natural compounds may have a cytotoxic effect, making them interesting alternatives to or candidates for integration into conventional therapeutic approaches. among mediterranean diet phenols, secoiridoid oleuropein ( ole ) is the most abundant phenolic compound in olea europaea l. tree leaves ( ole content up to 14 – 19 % in olive leaves ), followed by its degradation derivative hydroxytyrosol ( 3, 4 - dihydrox yphenylethanol, ht, 2. 28 mg / g of olive leaf extract ) ( figure 1 ). ole and ht are also found in the fruit of olea europaea l. and in olive oil; thus, they are easily ingested as part of a routine diet, but they can also be obtained from other sources, e. g., olive mill wastewater. both compounds have attracted attention for their accessibility, safe profile, powerful antioxidant and scavenging activity against reactive oxygen species ( ros ), and controversial anti-inflammatory action. for more than two decades, ole and ht ( together or alone ) have been the focus of intense research efforts in the context of infectious diseases and prevention / management of chronic non - communicable diseases, including cancer, with encouraging results from in vitro and in vivo models. on this basis, it would be difficult to understand the reasons behind the lack of systematic testing of ole and ht as supplements to prevent the insurgence of cancer or support the management of hematological malignancies and solid tumors. this becomes clearer considering that, despite promising proof in the field, experimental evidence about ole and ht bioavailability in humans and animals clearly demonstrates that ole and ht act as cancer - preventive agents and cytotoxic drugs mainly at concentrations far from plasma levels reachable through nu trit ion, an aspect often interpreted as marginal that we discuss in detail in this review. also, as explained in the following paragraphs, the complexity and diversity of molecular mechanisms resulting in net ole and ht action has led to questions regarding the possibility that these compounds might even facilitate the expansion of neoplastic clones at nu trit ionally relevant concentrations. in this review, we discuss the available data on the use of ole and ht as anti - cancer drugs and the feasibility of their application in the context of clinical routine now or in the near future. ole and ht activity against solid tumor insurgence and development has been challenged in a large number of experimental models, both in vivo and in vitro. no single shared molecular mechanism and / or triggered cellular response seems implicated in ole and ht cytotoxicity, resulting in an articulated frame that imposes a separate dissertation for every type of studied solid tumor. to facilitate critical interpretation, in each subsection, ole and ht assayed doses are indicated, with the half - maximal inhibitory concentration ( ic50 ) and the half - maximal effective concentration ( ec50 ) reported as exact values, mean ± standard deviation ( s. d. ), or mean ± standard error of the mean ( s. e. m. ) whenever provided by the authors. a list of experimental models used to study ole and ht cytotoxicity in cancer cells is reported in table 1.