Cellular senescence is a tumor suppression mechanism. We previously reported that CKII downregulation induces senescence in human lung fibroblast IMR-90 and colon cancer HCT116 cells. In this study, potential longevity drugs, including rapamycin, vitamin C, and vitamin E, blocked CKII downregulation-mediated senescence through reduction of reactive oxygen species (ROS) production in HCT116 cells. Since rapamycin is a mammalian target of rapamycin (mTOR) inhibitor, we examined the roles of mTOR and its upstream regulators phosphatidylinositol 3-kinase (PI3K) and AKT in CKII inhibition-mediated senescence. CKII alpha knock-down or CKII inhibitor treatment strikingly increased phosphorylation of mTOR, p70S6K, an mTOR substrate, and AKT, whereas CKII alpha overexpression reduced this phosphorylation event. This result indicated that CKII inhibition activated the PI3K-AKT-mTOR pathway. Further, pharmacological inhibition of PI3K and ART attenuated ROS production and senescence in CKII-downregulated cells. Taken together, these results demonstrate, for the first time, that the PI3K-AKT-mTOR-ROS pathway is necessary for CKII inhibition-mediated cellular senescence. (C) 2013 Elsevier Inc. All rights reserved.