As the immune cells kill tumor cells by releasing small cytotoxic proteins that cause apoptosis in target cells (24), we analyzed the expression profiles of 9 major genes encoding cytotoxic proteins, including FASLG, GNLY, GZMA, GZMB, GZMH, GZMM, IFNG, PRF1, TNF (25). Here, PRF1 is linked to neoplasm.