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BH3 mimetics, targeting Bcl-2 family anti-apoptotic proteins, represent a promising therapeutic opportunity in tumors. ABT-199, the first specific Bcl-2 inhibitor, has been approved by FDA for treating several hematological malignancies. We have recently discovered IS21, a novel pan BH3 mimetic with preclinical anti-tumor activity in different cancers. This study aimed to evaluate the efficacy of different BH3 mimetics both as single agents, in a panel of different tumor cell histotypes, and in combination with the currently used target therapy in ovarian cancer and melanoma. Our results demonstrate that IS21 reduced the viability of T-cell acute lymphoblastic leukemia, melanoma, lung, pancreatic and ovarian cancer cell lines, and that Bcl-xL and Mcl-1 protein levels were markers of IS21 sensitivity in melanoma and ovarian cancer, respectively. Exploring the IS21 mechanism of action, we reported that IS21 activity was dependent on BAX and BAK proteins, and complexes between Bcl-2 and Bcl-xL proteins and their main binding partners were reduced by IS21. In combination experiments, BH3 mimetics sensitized ovarian cancer cells to the treatment with PARP inhibitors, while IS21 and ABT-199 synergized with MAPK inhibitors in melanoma models both in vitro and in vivo. Through different methodological approaches, we evidenced that the potentiating effect of BH3 mimetics was related to enhancement of apoptotic pathway, both in melanoma and ovarian cancer. In conclusion, our data suggest the use of inhibitors of the anti-apoptotic proteins as a possible therapeutic strategy to enhance the efficacy of target therapy in ovarian cancer and melanoma.

The treatment and management of patients with metastatic melanoma have evolved considerably in the “era” of personalized medicine. Melanoma was one of the first solid tumors to benefit from immunotherapy; life expectancy for patients in advanced stage of disease has improved. However, many progresses have yet to be made considering the (still) high number of patients who do not respond to therapies or who suffer adverse events. In this scenario, precision medicine appears fundamental to direct the most appropriate treatment to the single patient and to guide towards treatment decisions. The recent multi-omics analyses (genomics, transcriptomics, proteomics, metabolomics, radiomics, etc.) and the technological evolution of data interpretation have allowed to identify and understand several processes underlying the biology of cancer; therefore, improving the tumor clinical management. Specifically, these approaches have identified new pharmacological targets and potential biomarkers used to predict the response or adverse events to treatments. In this review, we will analyze and describe the most important omics approaches, by evaluating the methodological aspects and progress in melanoma precision medicine.

Simple Summary The response to pharmacological treatments is deeply influenced by the tight interactions between the tumor cells and the microenvironment. In this review we describe, for melanoma, the most important mechanisms of resistance to targeted therapy and immunotherapy mediated by the components of the microenvironment. In addition, we briefly describe the most recent therapeutic advances for this pathology. The knowledge of molecular mechanisms, which are underlying of drug resistance, is fundamental for the development of new therapeutic approaches for the treatment of melanoma patients. Abstract Antitumor therapies have made great strides in recent decades. Chemotherapy, aggressive and unable to discriminate cancer from healthy cells, has given way to personalized treatments that, recognizing and blocking specific molecular targets, have paved the way for targeted and effective therapies. Melanoma was one of the first tumor types to benefit from this new care frontier by introducing specific inhibitors for v-Raf murine sarcoma viral oncogene homolog B (BRAF), mitogen-activated protein kinase kinase (MEK), v-kit Hardy–Zuckerman 4 feline sarcoma viral oncogene homolog (KIT), and, recently, immunotherapy. However, despite the progress made in the melanoma treatment, primary and/or acquired drug resistance remains an unresolved problem. The molecular dynamics that promote this phenomenon are very complex but several studies have shown that the tumor microenvironment (TME) plays, certainly, a key role. In this review, we will describe the new melanoma treatment approaches and we will analyze the mechanisms by which TME promotes resistance to targeted therapy and immunotherapy.

The mammalian target of rapamycin (mTOR) represents a critical hub for the regulation of different processes in both normal and tumor cells. Furthermore, it is now well established the role of mTOR in integrating and shaping different environmental paracrine and autocrine stimuli in tumor microenvironment (TME) constituents. Recently, further efforts have been employed to understand how the mTOR signal transduction mechanisms modulate the sensitivity and resistance to targeted therapies, also for its involvement of mTOR also in modulating angiogenesis and tumor immunity. Indeed, interest in mTOR targeting was increased to improve immune response against cancer and to develop new long-term efficacy strategies, as demonstrated by clinical success of mTOR and immune checkpoint inhibitor combinations. In this chapter, we will describe the role of mTOR in modulating TME elements and the implication in its targeting as a great promise in clinical trials.

The mammalian target of rapamycin (mTOR) represents a critical hub for the regulation of different processes in both normal and tumor cells. Furthermore, it is now well established the role of mTOR in integrating and shaping different environmental paracrine and autocrine stimuli in tumor microenvironment (TME) constituents. Recently, further efforts have been employed to understand how the mTOR signal transduction mechanisms modulate the sensitivity and resistance to targeted therapies, also for its involvement of mTOR also in modulating angiogenesis and tumor immunity. Indeed, interest in mTOR targeting was increased to improve immune response against cancer and to develop new long-term efficacy strategies, as demonstrated by clinical success of mTOR and immune checkpoint inhibitor combinations. In this chapter, we will describe the role of mTOR in modulating TME elements and the implication in its targeting as a great promise in clinical trials.

The threatening notoriety of pancreatic cancer mainly arises from its negligible early diagnosis, highly aggressive progression, failure of conventional therapeutic options and consequent very poor prognosis. The most important driver genes of pancreatic cancer are the oncogene KRAS and the tumor suppressors TP53, CDKN2A, and SMAD4. Although the presence of few drivers, several signaling pathways are involved in the oncogenesis of this cancer type, some of them with promising targets for precision oncology. Pancreatic cancer is recognized as one of immunosuppressive phenotype cancer: it is characterized by a fibrotic-desmoplastic stroma, in which there is an intensive cross-talk between several cellular (e.g., fibroblasts, myeloid cells, lymphocytes, endothelial, and myeloid cells) and acellular (collagen, fibronectin, and soluble factors) components. In this review; we aim to describe the current knowledge of the genetic/biological landscape of pancreatic cancer and the composition of its tumor microenvironment; in order to better direct in the intrinsic labyrinth of this complex tumor type. Indeed; disentangling the genetic and molecular characteristics of cancer cells and the environment in which they evolve may represent the crucial step towards more effective therapeutic strategies

To date, pancreatic cancer is still one of the most lethal cancers in the world, mainly due to the lack of early diagnosis and personalized treatment strategies. In this context, the possibility and the opportunity of identifying genetic and molecular biomarkers are crucial to improve the feasibility of precision medicine. In 2019, the World Health Organization classified pancreatic ductal adenocarcinoma cancer (the most common pancreatic tumor type) into eight variants, according to specific histomorphological features. They are: colloid carcinoma, medullary carcinoma, adenosquamous carcinoma, undifferentiated carcinoma, including also rhabdoid carcinoma, undifferentiated carcinoma with osteoclast-like giant cells, hepatoid carcinoma, and signet-ring/poorly cohesive cells carcinoma. Interestingly, despite the very low incidence of these variants, innovative high throughput genomic/transcriptomic techniques allowed the investigation of both somatic and germline mutations in each specific variant, paving the way for their possible classification according also to specific alterations, along with the canonical mutations of pancreatic cancer (KRAS, TP53, CDKN2A, SMAD4). In this review, we aim to report the current evidence about genetic/molecular profiles of pancreatic cancer variants, highlighting their role in therapeutic and clinical impact.

Breast cancer was one of the first malignancies to benefit from targeted therapy, i.e., treatments directed against specific markers. Inhibitors against HER2 are a significant example and they improved the life expectancy of a large cohort of patients. Research on new biomarkers, therefore, is always current and important. AXL, a member of the TYRO-3, AXL and MER (TAM) subfamily, is, today, considered a predictive and prognostic biomarker in many tumor contexts, primarily breast cancer. Its oncogenic implications make it an ideal target for the development of new pharmacological agents; moreover, its recent role as immune-modulator makes AXL particularly attractive to researchers involved in the study of interactions between cancer and the tumor microenvironment (TME). All these peculiarities characterize AXL as compared to other members of the TAM family. In this review, we will illustrate the biological role played by AXL in breast tumor cells, highlighting its molecular and biological features, its involvement in tumor progression and its implication as a target in ongoing clinical trials.

Mounting preclinical and clinical evidence indicates that rewiring the host immune system in favor of an antitumor microenvironment achieves remarkable clinical efficacy in the treatment of many hematological and solid cancer patients. Nevertheless, despite the promising development of many new and interesting therapeutic strategies, many of these still fail from a clinical point of view, probably due to the lack of prognostic and predictive biomarkers. In that respect, several data shed new light on the role of the tumor suppressor phosphatase and tensin homolog on chromosome 10 (PTEN) in affecting the composition and function of the tumor microenvironment (TME) as well as resistance/sensitivity to immunotherapy. In this review, we summarize current knowledge on PTEN functions in different TME compartments (immune and stromal cells) and how they can modulate sensitivity/resistance to different immunological manipulations and ultimately influence clinical response to cancer immunotherapy.

Background Human microsatellite-stable (MSS) colorectal cancers (CRCs) are immunologically “cold” tumour subtypes characterized by reduced immune cytotoxicity. The molecular linkages between immune-resistance and human MSS CRC is not clear. Methods We used transcriptome profiling, in silico analysis, immunohistochemistry, western blot, RT-qPCR and immunofluorescence staining to characterize novel CRC immune biomarkers. The effects of selective antagonists were tested by in vitro assays of long term viability and analysis of kinase active forms using anti-phospho antibodies. Results We identified the lymphocyte antigen 6 complex, locus G6D (LY6G6D) as significantly overexpressed (around 15-fold) in CRC when compared with its relatively low expression in other human solid tumours. LY6G6D up-regulation was predominant in MSS CRCs characterized by an enrichment of immune suppressive regulatory T-cells and a limited repertoire of PD-1/PD-L1 immune checkpoint receptors. Coexpression of LY6G6D and CD15 increases the risk of metastatic relapse in response to therapy. Both JAK-STAT5 and RAS-MEK-ERK cascades act in concert as key regulators of LY6G6D and Fucosyltransferase 4 (FUT4), which direct CD15-mediated immune-resistance. Momelotinib, an inhibitor of JAK1/JAK2, consistently abrogated the STAT5/LY6G6D axis in vitro, sensitizing MSS cancer cells with an intact JAK-STAT signaling, to efficiently respond to trametinib, a MEK inhibitor used in clinical setting. Notably, colon cancer cells can evade JAK2/JAK1-targeted therapy by a reversible shift of the RAS-MEK-ERK pathway activity, which explains the treatment failure of JAK1/2 inhibitors in refractory CRC. Conclusions Combined targeting of STAT5 and MAPK pathways has superior therapeutic effects on immune resistance. In addition, the new identified LY6G6D antigen is a promising molecular target for human MSS CRC. Electronic supplementary material The online version of this article (10.1186/s13046-018-1019-5) contains supplementary material, which is available to authorized users.

Cytokines are a family of soluble factors (Growth Factors (GFs), chemokines, angiogenic factors, and interferons), which regulate a wide range of mechanisms in both physiological and pathological conditions, such as tumor cell growth and progression, angiogenesis, and metastasis. In recent years, the growing interest in developing new cancer targeted therapies has been accompanied by the effort to characterize Tumor Microenvironment (TME) and Tumor-Stroma Interactions (TSI). The connection between tumor and stroma is now well established and, in the last decade, evidence from genetic, pharmacological, and epidemiological data supported the importance of microenvironment in tumor progression. However, several of the mechanisms behind TSI and their implication in tumor progression remain still unclear and it is crucial to establish their potential in determining pharmacological response. Many studies have demonstrated that cytokines network can profoundly affect TME, thus displaying potential therapeutic efficacy in both preclinical and clinical models. The goal of this review is to give an overview of the most relevant cytokines involved in colorectal and pancreatic cancer progression and their implication in drug response.

Colorectal cancer (CRC) still remains a disease with high percentage of death, principally due to therapy resistance and metastasis. During the time the hypothesis has been reinforced that CRC stem cells (CRCSC) are involved in allowing intratumoral heterogeneity, drug escape mechanisms and secondary tumors. CRCSC are characterized by specific surface markers (i.e., CD44 and CD133), signaling pathways activation (i.e., Wnt and Notch) and gene expression (i.e., Oct4 and Snail), which confer to CRCSC self-renewal abilities and pluripotent capacity. Interleukin (IL)-8 is correlated to CRC progression, development of liver metastases and chemoresistance; moreover, IL-8 modulates not only stemness maintenance but also stemness promotion, such as epithelial-mesenchymal transition. This review wants to give a brief and up-to-date overview on IL-8 implication in CRCSC cues.

Background Mounting evidence suggests that RAF-mediated MEK activation plays a crucial role in paradox MAPK (re)activation, leading to resistance and therapeutic failure with agents hitting a single step along the MAPK cascade. Methods We examined the molecular and functional effects of single and combined BRAF (dabrafenib), pan-RAF (RAF265), MEK (trametinib) and EGFR/HER2 (lapatinib) inhibition, using Western Blot and conservative isobologram analysis to assess functional synergism, and explored genetic determinants of synergistic interactions. Immunoprecipitation based assays were used to detect the interaction between BRAF and CRAF. The Mann-Whitney U test was used for comparing quantitative variables. Results Here we demonstrated that a combination of MEK and BRAF inhibitors overcomes paradoxical MAPK activation (induced by BRAF inhibitors) in BRAF-wt/RAS-mut NSCLC and PDAC in vitro. This results in growth inhibitory synergism, both in vitro and in vivo, in the majority (65%) of the cellular models analyzed, encompassing cell lines and patient-derived cancer stem cells and organoids. However, RAS mutational status is not the sole determinant of functional synergism between RAF and MEK inhibitors, as demonstrated in KRAS isogenic tumor cell line models. Moreover, in EGFR-driven contexts, paradoxical MAPK (re)activation in response to selective BRAF inhibition was dependent on EGFR family signaling and could be offset by simultaneous EGFR/HER-2 blockade. Conclusions Overall, our data indicate that RAF inhibition-induced paradoxical MAPK activation could be exploited for therapeutic purposes by simultaneously targeting both RAF and MEK (and potentially EGFR family members) in appropriate molecular contexts. KRAS mutation per se does not effectively predict therapeutic synergism and other biomarkers need to be developed to identify patients potentially deriving benefit from combined BRAF/MEK targeting. Electronic supplementary material The online version of this article (10.1186/s13046-018-0820-5) contains supplementary material, which is available to authorized users.

The mammalian Target of Rapamycin (mTOR) pathway plays an essential role in sensing and integrating a variety of exogenous cues to regulate cellular growth and metabolism, in both physiological and pathological conditions. mTOR functions through two functionally and structurally distinct multi-component complexes, mTORC1 and mTORC2, which interact with each other and with several elements of other signaling pathways. In the past few years, many new insights into mTOR function and regulation have been gained and extensive genetic and pharmacological studies in mice have enhanced our understanding of how mTOR dysfunction contributes to several diseases, including cancer. Single-agent mTOR targeting, mostly using rapalogs, has so far met limited clinical success; however, due to the extensive cross-talk between mTOR and other pathways, combined approaches are the most promising avenues to improve clinical efficacy of available therapeutics and overcome drug resistance. This review provides a brief and up-to-date narrative on the regulation of mTOR function, the relative contributions of mTORC1 and mTORC2 complexes to cancer development and progression, and prospects for mTOR inhibition as a therapeutic strategy.

Introduction One of the main obstacle to the successful development of therapeutic strategies remains the identification of biomarker underlying drug resistance. Recently, investigators have become more aware the role of the tumour microenvironment (TME) in cancer and the potential therapeutic opportunities that derive from suppressing potential resistance mechanisms arising microenvironmental interactions. The aim of this study was to set-up multicellular culture models to uncover the molecular mechanisms by which stromal/endothelial cells modulate response to signalling inhibitors and to identify potential therapeutic targets in PTEN-loss contexts. Material and methods Isogenic CRC cell lines (X-MAN HCT116 and HCT116 PTEN-/-) were treated with MAPKi and PI3K/mTORi alone or in combination, in the presence or absence of stromal fibroblasts or fibroblast/endothelial cell conditioned medium (CM). Cytofluorimetric analysis and Crystal Violet assay were used to analyse functional response to targeted agents; pathways activation and cytokine/chemokine profile were analysed using Western blot and ELISA assay respectively. Results and discussions In co-culture CRC models, the response to MAPK and PI3K inhibitors is the result of interaction between tumour cells and their surrounding stroma. Response to PI3K/mTORi is mainly influenced by microenvironmental interactions: direct cell-to-cell tumour/stroma contact renders stromal cells resistant to PI3K/mTORi, while the presence of stromal cell-derived soluble factors sensitises PTEN-competent CRC cells to PI3K/mTORi-mediated growth inhibition. This effect was confirmed using CM from different types of stromal cells (fibroblast/endothelial) that similarly affected the response of CRC cell lines to signalling inhibitors; this is probably due to similar profile of cytokine/chemokine production in stromal cell and is subjected to a ‘saturation’ effect. The presence of stromal CM upregulates MAPK activation regardless of PTEN status, whereas mTOR pathway upregulation is observed mainly in PTEN-competent CRC cells. Conclusion The presence of stromal cells (fibroblasts/endothelium) profoundly influences CRC response to PI3K/mTOR-targeting agents. Understanding the mechanisms underlying microenvironmental interactions (tumour, stroma, soluble factors) may be of fundamental importance to overcome therapeutic resistance and develop more effective therapies for patients affected by cancer.

Introduction HER2 (amplified in 30% of BC) is involved in the activation of many pathways and its function is regulated by HSP90. Thus, HSP90 co-targeting is emerging as a potential molecular target for HER2-directed BC therapy. Material and methods We analysed HER2 and HSP90 expression in a panel of BC cell lines, including MCF7 cells stably transfected with a constitutively active HER2. HER2/HSP90 expression and growth inhibition were monitored over time upon exposure to trastuzumab (T) and docetaxel (D), in the presence or absence of HSP90 silencing. We also retrospectively evaluated a series of 24 locally advanced/operable BC patients (pts) who underwent neoadjuvant T+D for HSP90 expression and correlated it with pathological complete response (pCR). Results and discussions In the BC cell lines analysed there was no clear-cut correlation between HSP90 and HER2 expression. HER2 transfection into MCF7 cells increased HSP90 mRNA and protein expression; however, treatment with T further increased HSP90 levels. Conversely D increased HER2, but did not affect HSP90, expression. In HER2 +BC cell lines, simultaneous T+D combination resulted in synergistic growth inhibition in vitro , while their staggered combination, particularly T followed by D, did not afford synergistic effects. Effects of simultaneous and staggered treatments on HSP90 and HER2 expression were analysed by WB: HER2 expression decreased in the simultaneous and staggered combination (D followed by T), while HSP90 expression did not change upon combined treatment. The effects of HSP90 silencing and overexepression on functional response to T+D are being analysed in HER2 +BC models: preliminary results indicate that HSP90 silencing in HER2 +BC decreases the therapeutic synergism of the simultaneous T+D combination. Accordingly, in locally advanced/operable pts undergoing neoadjuvant T+D, pCR occurred more frequently in pts with a baseline HSP90 score of 3+, as compared to 2+and 1+ (50.0% vs. 14.3% vs. none, p=0.05). These results suggest the possibility to classify HER2-positive pts into HSP90 defined subgroups and elaborate specific therapeutic strategies. Conclusion Preclinical data indicate that constitutive HER2 activation induces HSP90 expression and HSP90 modulation influences the functional response to combined treatment. Baseline HSP90 expression may potentially represent a pre-requisite of pharmacological response in HER2-addicted BC.

T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive blood cancer that comprises 10–15% of pediatric and ~25% of adult ALL cases. Although the curative rates have significantly improved over the past 10 years, especially in pediatric patients, T-ALL remains a challenge from a therapeutic point of view, due to the high number of early relapses that are for the most part resistant to further treatment. Considerable advances in the understanding of the genes, signaling networks, and mechanisms that play crucial roles in the pathobiology of T-ALL have led to the identification of the key drivers of the disease, thereby paving the way for new therapeutic approaches. PTEN is critical to prevent the malignant transformation of T-cells. However, its expression and functions are altered in human T-ALL. PTEN is frequently deleted or mutated, while PTEN protein is often phosphorylated and functionally inactivated by casein kinase 2. Different murine knockout models recapitulating the development of T-ALL have demonstrated that PTEN abnormalities are at the hub of an intricate oncogenic network sustaining and driving leukemia development by activating several signaling cascades associated with drug-resistance and poor outcome. These aspects and their possible therapeutic implications are highlighted in this review.

Identifying putative biomarkers of clinical outcomes in cancer is crucial for successful enrichment, and for the selection of patients who are the most likely to benefit from a specific therapeutic approach. Indeed, current research in personalized cancer therapy focuses on the possibility of identifying biomarkers that predict prognosis, sensitivity or resistance to therapies. Phosphatase and tensin homolog deleted on chromosome 10 (PTEN) is a tumor suppressor gene that regulates several crucial cell functions such as proliferation, survival, genomic stability and cell motility through both enzymatic and non-enzymatic activities and phosphatidylinositol 3-kinase (PI3K)-dependent and -independent mechanisms. Despite its undisputed role as a tumor suppressor, assessment of PTEN status in sporadic human tumors has yet to provide clinically robust prognostic, predictive or therapeutic information. This is possibly due to the exceptionally complex regulation of PTEN function, which involves genetic, transcriptional, post-transcriptional and post-translational events. This review shows a brief summary of the regulation and function of PTEN and discusses its controversial aspects as a prognostic/predictive biomarker.

Combined MAPK/PI3K pathway inhibition represents an attractive, albeit toxic, therapeutic strategy in oncology. Since PTEN lies at the intersection of these two pathways, we investigated whether PTEN status determines the functional response to combined pathway inhibition. PTEN (gene, mRNA, and protein) status was extensively characterized in a panel of cancer cell lines and combined MEK/mTOR inhibition displayed highly synergistic pharmacologic interactions almost exclusively in PTEN-loss models. Genetic manipulation of PTEN status confirmed a mechanistic role for PTEN in determining the functional outcome of combined pathway blockade. Proteomic analysis showed greater phosphoproteomic profile modification(s) in response to combined MEK/mTOR inhibition in PTEN-loss contexts and identified JAK1/STAT3 activation as a potential mediator of synergistic interactions. Overall, our results show that PTEN-loss is a crucial determinant of synergistic interactions between MAPK and PI3K pathway inhibitors, potentially exploitable for the selection of cancer patients at the highest chance of benefit from combined therapeutic strategies.

Our understanding of the genetic and non-genetic molecular alterations associated with colorectal cancer (CRC) progression and therapy resistance has markedly expanded in the recent years. In addition to their effects on tumor biology, targeted therapies can have effects on host immune responses. However, the mechanisms by which immune cells organize tumor microenvironments to regulate T-cell activity need to be comprehensively defined. There is good evidence in the literature that alterations in different members of the MAPK superfamily (mainly ERKs and p38 MAPKs) modify the inflammatory response and antitumor immunity, enhancing metastatic features of the tumors. In addition, a plethora of alterations that emerge at relapse often converge on the activation of MAPKs, particularly, ERKs, which act in concert with other oncogenic signals to modulate cellular homeostasis and clonal evolution during targeted therapies. Herein, we discuss how this knowledge can be translated into drug development strategies aimed at increasing tumor antigenicity and antitumor immune responses. Insights from these studies could provide a framework for considering additional combinations of targeted therapies and immunotherapies for the treatment of CRC.

Introduction PTEN is a protein that restrains cells from growing unchecked; when it is absent or not functioning (as it often happens in prostate and colorectal cancer - CRC), cancer develops more easily and grows in a more aggressive and therapy-resistant fashion. However, just measuring PTEN mutational status or gene/protein levels in clinical samples may not be sufficient to assess its function, as its regulation is complex. Therefore, we analysed miRNA, transcriptomic, and proteomic profiles of isogenic CRC models differing for PTEN status, in order to identify a set of genes or proteins that are stably modulated by the presence or absence of a functional PTEN. Material and methods To identify biomarkers of PTEN loss of function and functional downstream effectors of PTEN activity, the isogenic CRC cell lines HCT116 (PTEN+/+) and HCT116 PTEN-/-(Horizon Discovery Ltd) were subjected to comprehensive miRNA profiling (Human miRNA Microarray Release 21, Agilent), transcriptomic analysis (NextSeq 500, Illumina), and semi-quantitative phosphoproteomic analysis (Antibody Microarray Service, KinexTM). Results and discussions miRNA profiling found 18 miRNAsdifferentially expressed in HCT116 PTEN+/+ and their HCT116 PTEN-/- counterpart: only miR-196a-5p is up-regulated in HCT116 PTEN-/-, whereas other 17 miRNAs were all down-regulated; several of these target miRNAs have been validated by qRT-PCR. RNA-Seq data were analysed via the RAP pipeline available at CINECA that relies on the Tuxedo suite (Tophat-Cufflinks-Cuffdiff) for read mapping, transcript abundance estimation and transcript or gene-based differential expression. RNA-Seq analysis showed 247 differentially expressed genes in HCT116 PTEN+/+ cells as compared to HCT116 PTEN-/- (159 up-regulated and 88 down-regulated in HCT116 PTEN-/-) and clustering into 9 subgroups (including: tissue morphogenesis; negative regulation of phosphatase metabolic process; regulation of sequence-specific DNA binding transcription factor activity). qRT-PCR assay of 10 dysregulated genes was performed to validate the RNA-Seq data set. Proteomic analysis showed that 92 proteins (25 total proteins and 67 phospho-proteins) are differentially expressed in HCT116 PTEN+/+ and their HCT116 PTEN-/- counterpart, some of which have been validated by WB. Conclusion Our data identify differentially expressed sets of miRNA/genes/proteins between HCT116 PTEN+/+ and HCT116 PTEN-/-. Bioinformatics analysis to cluster these sets into functional PTEN-loss ‘signatures’ is ongoing.

Introduction Mutational status in CRC is a strong predictor for overall survival; unfortunately, tumour microenvironment (TME) and tumor-stroma interactions (TSI) also increase cancer cells’ drug resistance, leading to an urgent need to better understand the molecular mechanisms of acquired tumor-resistance, which remains crucial to determine overall patient benefit. Material and methods Production of IL-8 and vascular endothelial growth factor (VEGF) was determined by ELISA under standardised culture conditions. Modulation of cytokine production after exposure to selective inhibitors of the MAPK and PI3K pathways was assessed, by both ELISA assay and real time-PCR. BRAF, MEK1, ERK1 and ERK2 expression were modulated using siRNAs specifically targeting these genes. Results and discussions CRC cell lines harbouring both BRAFV600E and PTEN-loss expressed the highest levels of IL-8 and a ROC curve-based prediction algorithm based on these two mutations had 68% accuracy in predicting IL-8 production (p=0.002); on the other hand, VEGF levels inversely correlated with KRAS mutational status. IL-8 is tightly and transcriptionally controlled by activation of the MEK/ERK pathway, as the MEK inhibitor trametinib downregulated ERK Thr202/Tyr204 phosphorylation in the nuclear compartment and profoundly suppressed IL-8 production regardless of the genetic background; conversely, the selective BRAF inhibitor dabrafenib downregulated IL-8 only in BRAFV600E contexts, but upregulated its production in parallel with ERK Thr202/Tyr204 and STAT3 Ser727 phosphorylation in the nuclear compartment of BRAF-wt CRC cells. PI3K/mTOR inhibitors did not significantly modulate IL-8 production, confirming that the IL-8 release is downstream the BRAF/MEK/ERK pathway. In order to better investigate the role of MAPK pathway in IL-8 regulation, components of the MAPK-signalling pathways (BRAF, MEK, ERK1 and ERK2) were silenced by siRNA: IL-8 production was significantly downregulated after BRAF, MEK, or ERK2 silencing, regardless of the BRAF mutational status; conversely, no effects on IL-8 expression were observed after ERK1 silencing. Conclusion These results showed that, in preclinical models of CRC, IL-8 expression is regulated by a BRAF/MEK/ERK2/STAT3 axis, and differential modulation of IL-8 after pharmacological treatments is dependent on BRAF mutational status. Such evidence allows better understanding of the molecular mechanisms of chemokine regulation, which can, in turn, contribute to the development of new targeted therapies in CRC.

PTEN is the most important negative regulator of the PI3K signaling pathway. In addition to its canonical, PI3K inhibition-dependent functions, PTEN can also function as a tumor suppressor in a PI3K-independent manner. Indeed, the PTEN network regulates a broad spectrum of biological functions, modulating the flow of information from membrane-bound growth factor receptors to nuclear transcription factors, occurring in concert with other tumor suppressors and oncogenic signaling pathways. PTEN acts through its lipid and protein phosphatase activity and other non-enzymatic mechanisms. Studies conducted over the past 10 years have expanded our understanding of the biological role of PTEN, showing that in addition to its ability to regulate proliferation and cell survival, it also plays an intriguing role in regulating genomic stability, cell migration, stem cell self-renewal, and tumor microenvironment. Changes in PTEN protein levels, location, and enzymatic activity through various molecular mechanisms can generate a continuum of functional PTEN levels in inherited syndromes, sporadic cancers, and other diseases. PTEN activity can indeed, be modulated by mutations, epigenetic silencing, transcriptional repression, aberrant protein localization, and post-translational modifications. This review will discuss our current understanding of the biological role of PTEN, how PTEN expression and activity are regulated, and the consequences of PTEN dysregulation in human malignant tumors.

Phosphatase and tensin homolog deleted on chromosome ten (PTEN) is a non-redundant lipid phosphatase that restrains and fine tunes the phosphatidylinositol-3-kinase (PI3K) signaling pathway. PTEN is involved in inherited syndromes, which predispose to different types of cancers and is among the most frequently inactivated tumor suppressor genes in sporadic cancers. Indeed, loss of PTEN function occurs in a wide spectrum of human cancers through a variety of mechanisms, including mutations, deletions, transcriptional silencing, or protein instability. PTEN prevents tumorigenesis through multiple mechanisms and regulates a plethora of cellular processes, including survival, proliferation, energy metabolism and cellular architecture. Moreover, recent studies have demonstrated that PTEN is able to exit, exist, and function outside the cell, allowing for inhibition of the PI3K pathway in neighboring cells in a paracrine fashion. Most recently, studies have shown that PTEN is also critical for stem cell maintenance and that PTEN loss can lead to the emergence and proliferation of cancer stem cell (CSC) clones. Depending on the cellular and tissue context of origin, PTEN deletion may result in increased self-renewal capacity or normal stem cell exhaustion and PTEN-deficient stem and progenitor cells have been reported in prostate, lung, intestinal, and pancreatic tissues before tumor formation; moreover, reversible or irreversible PTEN loss is frequently observed in CSC from a variety of solid and hematologic malignancies, where it may contribute to the functional phenotype of CSC. In this review, we will focus on the role of PTEN expression and function and downstream pathway activation in cancer stem cell biology and regulation of the tumorigenic potential; the emerging role of PTEN in mediating the crosstalk between the PI3K and MAPK pathways will also be discussed, together with prospects for the therapeutic targeting of tumors lacking PTEN expression.