CTLA4 and melanoma: Additionally, the PKHD1L1 expression was found to be predominantly high in B cells and plasma cells in GSE120575, in which samples were collected from melanoma patients treated with checkpoint inhibitors, anti-programmed death receptor 1 (PD-1), and anti-cytotoxic T-lymphocyte-associated protein-4 (CTLA-4) [35], as shown in Figure 4.