Interleukin-12 inhibits the survival of human colon cancer stem cells in vitro and their tumor initiating capacity in mice

Interleukin-12 (IL-12) is a potent immunomodulatory cytokine with unknown direct effect on the property of cancer stem cells (CSCs). In this study, we investigated the capacity of IL-12 to regulate the self-renewal and differentiation of human colon CSCs in vitro, as well as the effect of IL-12 on the growth of tumors initiated by CSCs in mice. After over-expression of IL-12 with lentiviral transfection, CSCs exhibited reduced invasiveness and tumorsphere formation in association with increased apoptosis in vitro. After injection into NOD/SCID mice, tumors initiated by CSCs transfected with IL-12 showed markedly reduced rate of growth. Mechanistic studies revealed that over-expression of IL-12 reduced the expression of IL-4 and STAT6 in CSCs. Thus, our study demonstrates a potentially beneficial role of IL-12 in directly limiting the malignant phenotype of CSCs.