XIAP and cancer: However, a significant reorganization of the signaling network observed, including down regulation of tumor suppressors (p-p53 and CHK1 when XIAP silenced or p-RB when CDK6 silenced) and upregulation of tumor promoting proteins (ETS1 when XIAP silenced or p-CREB when CDK6 silenced), which may confer the growth benefit for cancer cells.