PO-158 Extracellular vesicles, generated from UVA-exposed melanoma cells, promotes cell proliferation and invasion

Abstract

IntroductionUltraviolet radiation (UV) is the major risk factor for malignant melanoma. We have made the novel finding that melanocytes damaged by UVA, but not UVB, show plasma membrane damage that is readily repaired by lysosomal exocytosis. The exocytosis process is immediately followed by shedding of extracellular vesicles (EVs) from the cells. The generated EVs contain lysosomal marker proteins and microRNA that may affect neighbouring cells. The aim of our study is to investigate how isolated UVA-generated EVs affect cell proliferation and invasion of malignant melanoma cells.Material and methodsMelanoma cell cultures were exposed to UV irradiation and EVs were purified from conditioned media. The EVs were added to new cell cultures and gene expression analysis was performed to identify central signalling pathways. The candidate genes and miRNAs in UV-induced intercellular communication and in melanoma progression are verified and function tested in cell culture models of normal skin cells and malignant melanoma.Results and discussionsData analysis show up-regulation of 127 genes (FC >1.5) and in depth bioinformatic analysis identify TGF-β/SMAD signalling and associated microRNAs (mir21, mir24-2, mir200c) as candidate signalling molecules. In accordance, transfection with mir21 mimic induce proliferation in melanocytes, as well as in melanoma cells. Isolated EVs contained TGF-β, which promoted melanoma cell migration and invasion. Interestingly, melanoma cells spontaneously release EVs and mir21 is upregulated in melanoma progression.ConclusionUV-irradiation cause generation of extracellular vesicles with prophecy to stimulate cell proliferation and dissemination. UV-irradiation is an important component not only for the initiation of malignant melanoma but also for its progression.