LncRNA SAMMSON Mediates Adaptive Resistance to RAF Inhibition in BRAF-Mutant Melanoma Cells

The long noncoding RNA (lncRNA) SAMMSON is required for human melanoma cell growth and survival. However, whether SAMMSON regulates the response of mutant BRAF melanoma cells to RAF inhibitors remains unknown. In this work, we showed that SAMMSON is rapidly induced upon inhibition of ERK signaling, and SAMMSON overexpression conferred resistance to vemurafenib-induced cytotoxicity in melanoma cells. SOX10 mediated transcriptional induction of SAMMSON by vemurafenib, and SOX10 sumoylation at K55 was essential for this function. In addition, depletion of SAMMSON activated p53 signaling, which is dependent on the SAMMSON-interacting protein CARF. Depletion of SAMMSON sensitized mutant BRAF melanoma cells to RAF inhibitors in vitro and in vivo, while CARF knockdown reversed the enhanced sensitivity. In summary, these findings suggest that SAMMSON may function as a new mediator of adaptive resistance to RAF inhibitors in melanoma by modulating CARF-p53 signaling. SIGNIFICANCE: This study highlights the role of a SAMMSON/CARF/p53 signaling axis in modulating the adaptive resistance of mutant BRAF melanoma to RAF inhibitors.