As an immunotherapeutic option, cytotoxic T lymphocytes (CTLs) can selectively induce apoptosis in target cells via perforin/granzyme and Fas/tumor necrosis factor-mediated mechanisms, further serving as potential candidates for the treatment of cancers (10, 11); in fact, several previous studies have revealed the potential of CTLs to target specific types of cancer stem cells (CSCs), such as colon lung CSCs (12, 13). This evidence concerns the gene PRF1 and cancer.