The tumor suppressive activity of SIP1 has been appreciated by several studies, in which SIP1 has been shown to induce G1 phase cell cycle arrest by inhibiting cyclin D1 expression in squamous carcinoma cells, or to repress hTERT expression, resulting in replicative senescence in HCC cells [25, 34]. The gene discussed is CCND1; the disease is hepatocellular carcinoma.