Abstract: Cellular senescence is a permanent cell cycle arrest that may prevent aged or abnormal cells from further expansion and is therefore a safeguard mechanism against unlimited cell proliferation. Recent studies demonstrated that oncogene-induced senescence could prevent neoplastic transformation in vitro and in vivo, and oncogene might cause tumors only in senescence deficient cells. Although the mechanism of the cellular senescence has not been completely illustrated, activation of p16INK4a-RB and ARF-p53 pathways has been implicated in this process. Further investigation of the signaling pathways leading to senescence may offer new avenues for tumor treatment.