We first tested the transfected cells in athymic nude mice and found that Arf1 knockdown or inhibition did not affect the tumorigenic capability of B16-F10, CT26, or 4T1 cells in the immune-deficient mice (Supplementary Fig. 9f–h), suggesting that the anti-tumor activity of Arf1 knockdown does not occur through a directly cytotoxic effect on tumor cells. Here, ARF1 is linked to neoplasm.