CIP2A and cancer: However, we found that CIP2A, a protein that is overexpressed in cancers and shown to bind MYC and prevent PP2A from dephosphorylating Ser 6233, was robustly downregulated upon treatment with either YM155 (Fig. 4D, top panels, compare lanes 1 and 2 for each cell line) or siRNAs that target Survivin (Fig. S4C).