Keratinocyte-derived exosomal miR-31-5p reduces vemurafenib sensitivity in melanoma cells

Resistance to BRAF^V600E inhibitors (e.g., vemurafenib) remains a major challenge in malignant melanoma treatment. Keratinocytes influence melanoma cell sensitivity to vemurafenib, but the role of keratinocyte-derived exosomes in melanoma cell sensitivity to vemurafenib remains unclear.

In this study, we aimed to investigate the effects and mechanisms of keratinocyte-derived exosomes on melanoma cell growth and sensitivity to vemurafenib.

Exosomes were extracted from HaCaT keratinocytes. The growth of melanoma cell line A375 and UACC62 was assessed in vitro and in vivo. miRNA profiles of HaCaT-derived exosomes were characterized using RNA sequencing. miR-31-5p, AlkB homolog 1 (ALKBH1), and RNA m6A levels in A375 and UACC62 cells were evaluated using qRT-PCR, Western blotting, and RNA immunoprecipitation (RIP) assays.

HaCaT-derived exosomes promoted melanoma cell growth and reduced their sensitivity to vemurafenib both in vitro and in vivo. Exosomes from vemurafenib-treated HaCaT cells had stronger effects. Vemurafenib treatment increased miR-31-5p levels in HaCaT-derived exosomes, which subsequently upregulated miR-31-5p in recipient melanoma cells. The miR-31-5p inhibitor and the m6A inhibitor cycloleucine blocked exosome-induced proliferation, increases in global m6A levels, and decreases in vemurafenib sensitivity. ALKBH1, a typical demethylase of nucleic acids, was a direct target of miR-31-5p. ALKBH1 overexpression reversed exosome- and miR-31-5p mimic-induced changes in ALKBH1 expression, m6A levels, proliferation, and vemurafenib sensitivity.

Vemurafenib increases miR-31-5p in keratinocyte-derived exosomes, which suppresses ALKBH1 and elevates RNA m6A in melanoma cells, thereby promoting proliferation and reducing vemurafenib sensitivity. Targeting the miR-31-5p/ALKBH1 axis and m6A modification may offer a potential therapeutic strategy to enhance vemurafenib sensitivity in BRAF^V600E melanoma cells.