FOXO1 and hepatocellular carcinoma: Indeed, transfection of SKI human HCC cells (expressing low SKP2 levels) with wild-type SKP2 cDNA increased the proliferation rate proportionally to SKP2 expression, concomitantly triggering downregulation of multiple tumor suppressor proteins, including P21WAF1, P27KIP1, P57KIP2, P130, FOXO1, and RASSF1A [38].