FUNCTIONAL DROP-OUT SCREENINGS IDENTIFY ACTIONABLE VULNERABILITIES TO HALT MELANOMA GROWTH AND METASTASIS FORMATION

Advanced and metastatic melanoma prognosis is poor. Recent approval of targeted and immune therapies markedly improved overall survival rates, but nevertheless, the majority of patients experience recurrence and resistance, as well as treatment discontinuation due to severe toxicities. To explore new promising therapeutic approach in melanoma, I made use of our cohort of metastatic melanoma patient-derived xenografts (PDXs) to perform drop-out genetic screens, by means of a shRNA library targeting actionable genes, for which drugs are already available and can be repurposed for melanoma treatment. An innovative ex vivo transwell-based migration screen allowed me to isolate numerous actionable vulnerabilities, concordantly essential also for in vivo tumor growth, thus showing that this ex vivo migration system can be exploited as a valuable preclinical platform to assess patients sensitivity profiles. Based on these results, I identified one promising combinatorial therapy approach, that notably showed remarkable efficacy when tested in vivo. Moreover, in order to specifically investigate the metastatic process, I set up a relevant model of spontaneous metastasis, in which I performed drop-out actionable screen. Many metastasis-specific actionable dependencies were isolated, notably proving high functional heterogeneity among individual lesions. Several identified candidates showed unanticipated role in driving melanoma metastasis and I further studied one of them, whose silencing reduced melanoma invasion and metastasis formation, suggesting that its therapeutic exploitation could represent an innovative treatment approach to inhibit melanoma metastasis dissemination.