Abstract 1070: miR-579-3p is a novel master regulator of melanoma progression and drug resistance in metastatic melanoma

Abstract

Abstract Introduction: Malignant melanoma is the most aggressive form of skin cancer presenting in approximately 50% of cases activating mutations in the BRAF oncogene. For these patients new therapeutic options are represented by the combination of BRAF inhibitors and MEK-inhibitors. However, a major limitation is the occurrence of resistance related in the majority of cases to mutations causing either reactivation of the MAPK/ERK pathway or of the PI3K/PTEN/AKT pathway. This complex scenario is worsened by the absence, in a significant proportion of cases, of new mutations. This suggests the involvement also of epigenetic or post-transcriptional changes at the basis of resistance. We have focused our attention over the past years to adaptive changes occurring in melanoma cells upon exposure to BRAF and/or MEK inhibitors in order to identify new therapeutic targets. Here we hypothesize that miRNAs deregulation upon cell exposure to kinase inhibitors may contribute to the development of drug resistance. Experimental procedures: The involvement of specific miRNAs in the establishment of drug resistance in melanoma was investigated through the online software miRò while target predictions were performed with TargetScan and microrna.org. Impact on melanoma cell growth, migration and establishment of drug resistance was assessed through enforced-transient miR overexpression. Tumor biopsies were obtained from patients before therapy with kinase inhibitors or after relapse and used for RNA extraction. Results: We identified by bioinformatics analysis a novel miRNA, miR-579-3p, relevant for BRAF mutated melanoma progression and found that it targets both BRAF, the relevant oncoprotein in these melanomas, and MDM2. miR-579-3p expression levels are high in nevi, heavily decline in stage III-IV melanomas and further decrease in melanomacells selected in vitro for resistance to BRAF and/or MEK inhibitors. Through in vitro studies we obtained evidence that mir-579-3p is able to inhibit melanoma cell growth and migration and to induce apoptosis alone or in combination with BRAF and/or MEKi. Moreover we found that miR-579-3p overexpression impairs the establishment of resistance to BRAFi in human melanoma cells. Finally we found this miR to be down-regulated in tumor samples obtained from patients who developed resistance to target therapies and its expression to be inversely correlated to the expression levels of its target genes, BRAF and MDM2. Conclusions: Our results strongly demonstrate that miR-579-3p is a novel oncosuppressor miRNA, controlling melanoma progression and development of drug resistance and which could be used as a new therapeutic target for intervention. Citation Format: Luigi Fattore, Mario Acunzo, Giulia Romano, Alessandro Laganà, Debora Malpicci, Maria Elena Pisanu, Antonio Maria Grimaldi, Franco Fulciniti, Carlo Maria Croce, Rita Mancini, Paolo Antonio Ascierto, Gennaro Ciliberto. miR-579-3p is a novel master regulator of melanoma progression and drug resistance in metastatic melanoma. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1070.