BRAF inhibitors were approved for the treatment of BRAF-mutant melanoma. However, most patients acquire the resistance to BRAF inhibitors after several months of treatment. miR-524-5p is considered as a tumor suppressor in many cancers, including melanoma. In this study, we investigated the biological functions of miR-524-5p in melanoma with acquired resistance to BRAF inhibitor and evaluated the endogenous miR-524-5p expression as a biomarker for melanoma. The results showed that the expression of miR-524-5p was 0.481-fold lower in melanoma tissues (n = 117) than in nevus tissues (n = 40). Overexpression of miR-524-5p significantly reduced proliferative, anchorage-independent growth, migratory and invasive abilities of BRAF inhibitor-resistant melanoma cells. Moreover, the introduction of miR-524-5p led to a reduced development of BRAF inhibitor-resistant melanoma in vivo. Remarkably, the MAPK/ERK signaling pathway was decreased after treatment with miR-524-5p. Furthermore, next-generation sequencing analysis implied that the complement system, leukocyte extravasation, liver X receptor/retinoid-X-receptor activation, and cAMP-mediated signaling may be related to miR-524-5p-induced pathways in the resistant cells. The miR-524-5p level was higher on average in complete response and long-term partial response patients than in progressive disease and short-term partial response patients treated with BRAF inhibitors. Our results proposed that miR-524-5p could be considered as a target for treatment BRAF inhibitor-resistant melanoma and a prognostic marker in the response of patients to BRAF inhibitors for melanoma.

To describe the treatment patterns of nivolumab and ipilimumab in Japan, a retrospective observational study was conducted in melanoma patients who received nivolumab and ipilimumab sequentially. Patients who received nivolumab and ipilimumab in combination were excluded from this study. Efficacy was evaluated by the Response Evaluation Criteria in Solid Tumors (RECIST) in terms of the overall response rate (ORR), progression‐free survival (PFS), and disease control rate (DCR). Overall survival (OS) was also evaluated. Safety was assessed by the Common Terminology Criteria for Adverse Events (CTCAE). The treatment for all 68 patients enrolled involved switching from nivolumab to ipilimumab in 61 patients and switching from ipilimumab to nivolumab in seven patients. Switching occurred because of progressive disease in 55 patients and adverse events in eight patients. The median number of ipilimumab doses was three. Ipilimumab treatment achieved an ORR and DCR of 4.9% and 21.3%, respectively, and the median OS from start of ipilimumab was 7.0 months. During the study period, no new safety signals were noted. Independent factors which were indicative of poor prognosis for PFS were high neutrophil‐to‐lymphocyte ratio (NLR) and high C‐reactive protein (CRP) levels before ipilimumab treatment. An evaluation over a washout period indicated that no significant relationship existed with efficacy or safety. For the sequential administration of nivolumab and ipilimumab in Japanese melanoma patients, switch from nivolumab to ipilimumab was common, and the major reason for switching was progressive disease. The major prognostic factors for ipilimumab PFS after nivolumab were NLR and CRP before ipilimumab treatment.