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.

BackgroundThe potential predictive role of programmed death-ligand-1 (PD-L1) expression on tumor cells in the context of solid tumor treated with checkpoint inhibitors targeting the PD-1 pathway represents an issue for clinical research.MethodsOverall response rate (ORR) was extracted from phase I-III trials investigating nivolumab, pembrolizumab and MPDL3280A for advanced melanoma, non-small cell lung cancer (NSCLC) and genitourinary cancer, and cumulated by adopting a fixed and random-effect model with 95% confidence interval (CI). Interaction test according to tumor PD-L1 was accomplished. A sensitivity analysis according to adopted drug, tumor type, PD-L1 cut-off and treatment line was performed.ResultsTwenty trials (1,475 patients) were identified. A significant interaction (p<0.0001) according to tumor PD-L1 expression was found in the overall sample with an ORR of 34.1% (95% CI 27.6-41.3%) in the PD-L1 positive and 19.9% (95% CI 15.4-25.3%) in the PD-L1 negative population. ORR was significantly higher in PD-L1 positive in comparison to PD-L1 negative patients for nivolumab and pembrolizumab, with an absolute difference of 16.4% and 19.5%, respectively. A significant difference in activity of 22.8% and 8.7% according to PD-L1 was found for melanoma and NSCLC, respectively, with no significant difference for genitourinary cancer.ConclusionOverall, the three antibodies provide a significant differential effect in terms of activity according to PD-L1 expression on tumor cells. The predictive value of PD-L1 on tumor cells seems to be more robust for anti-PD-1 antibody (nivolumab and pembrolizumab), and in the context of advanced melanoma and NSCLC.

Background:The role of second-line chemotherapy (CT) is not established in advanced biliary tract cancer (aBTC). We investigated the outcome of aBTC patients treated with second-line CT and devised a prognostic model.Methods:Baseline clinical and laboratory data of 300 consecutive aBTC patients were collected and association with overall survival (OS) was investigated by multivariable Cox models.Results:The following parameters resulted independently associated with longer OS: Eastern Cooperative Oncology Group performance status of 0 (P<0.001; hazard ratio (HR), 0.348; 95% confidence interval (CI) 0.215–0.562), CA19.9 lower than median (P=0.013; HR, 0.574; 95% CI 0.370–0.891), progression-free survival after first-line CT ⩾6 months (P=0.027; HR, 0.633; 95% CI 0.422–0.949) and previous surgery on primary tumour (P=0.027; HR, 0.609; 95% CI 0.392–0.945). We grouped the 249 patients with complete data available into three categories according to the number of fulfilled risk factors: median OS times for good-risk (zero to one factors), intermediate-risk (two factors) and poor-risk (three to four factors) groups were 13.1, 6.6 and 3.7 months, respectively (P<0.001).Conclusions:Easily available clinical and laboratory factors predict prognosis of aBTC patients undergoing second-line CT. This model allows individual patient-risk stratification and may help in treatment decision and trial design.

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Due to extremely poor prognosis, pancreatic cancer (PDAC) represents the fourth leading cause of cancer-related death in Western countries. For more than a decade, gemcitabine (Gem) has been the mainstay of first-line PDAC treatment. Many efforts aimed at improving single-agent Gem efficacy by either combining it with a second cytotoxic/molecularly targeted agent or pharmacokinetic modulation provided disappointing results. Recently, the field of systemic therapy of advanced PDAC is finally moving forward. Polychemotherapy has shown promise over single-agent Gem: regimens like PEFG-PEXG-PDXG and GTX provide significant potential advantages in terms of survival and/or disease control, although sometimes at the cost of poor tolerability. The PRODIGE 4/ACCORD 11 was the first phase III trial to provide unequivocal benefit using the polychemotherapy regimen FOLFIRINOX; however the less favorable safety profile and the characteristics of the enrolled population, restrict the use of FOLFIRINOX to young and fit PDAC patients. The nanoparticle albumin-bound paclitaxel (nab-Paclitaxel) formulation was developed to overcome resistance due to the desmoplastic stroma surrounding pancreatic cancer cells. Regardless of whether or not this is its main mechanisms of action, the combination of nab-Paclitaxel plus Gem showed a statistically and clinically significant survival advantage over single agent Gem and significantly improved all the secondary endpoints. Furthermore, recent findings on maintenance therapy are opening up potential new avenues in the treatment of advanced PDAC, particularly in a new era in which highly effective first-line regimens allow patients to experience prolonged disease control. Here, we provide an overview of recent advances in the systemic treatment of advanced PDAC, mostly focusing on recent findings that have set new standards in metastatic disease. Potential avenues for further development in the metastatic setting and current efforts to integrate new effective chemotherapy regimens in earlier stages of disease (neoadjuvant, adjuvant, and multimodal approaches in both resectable and unresectable patients) are also briefly discussed.