Merkel cell polyomavirus and human papilloma virus in proliferative skin lesions arising in patients treated with BRAF inhibitors

The potential role of oncogenic viruses mediating development of proliferative skin lesions in patients treated with RAF inhibitors is poorly understood. The objective of this study was to investigate human papilloma virus (HPV) and Merkel cell polyomavirus (MCPyV) in skin lesions among patients treated with RAF inhibitors with the help of a case series describing prevalence of HPV, MCPyV, and RAS mutations in skin biopsies obtained from patients receiving RAF inhibitors and developing cutaneous lesions. HPV-DNA was amplified by PCR utilizing multiple nested primer systems designed for detection of a broad range of HPV types. MCPyV copy number determination with real time PCR technology was performed by a “Quantification of MCPyV, small t region” kit. Thirty-six patients were tested (squamous cell carcinoma (SCC) = 14; verruca vulgaris = 15; other = 11). Nine of 12 SCCs (75 %) and eight of 13 verruca vulgaris lesions (62 %) tested positive for MCPyV whereas none of the normal skin biopsies obtained from nine of these patients tested positive for MCPyV (p = 0.0007). HPV incidence in cutaneous SCCs was not different compared to normal skin (50 vs. 56 %, p = 0.86). The association between MCPyV and proliferative skin lesions after RAF inhibitor therapy merits further investigation.