PERP and Merkel cell skin cancer: We first assessed the relative expression of mRNA coding for PERP, the 2 TP63 isoforms (TAP63 and ΔNP63) and TP53 in six MCC cell lines (WaGa, MKL-1, MKL-2, UM-MCC002, UM-MCC005, UM-MCC034) by qPCR.