Oncoprotein that inhibits PP2A and stabilizes MYC in human malignancies. Promotes anchorage-independent cell growth and tumor formation. Homodimer (PubMed:28174209). Interacts with MYC (PubMed:17632056). Interacts with PPP2R5C; this interaction stabilizes CIP2A (PubMed:28174209). Interacts with PPP2R1A; this interaction stabilizes CIP2A (PubMed:28174209). Slightly concentrates in the perinuclear region (PubMed:12118381). Expressed at low levels in most of the tissues. Overexpressed in head-and-neck squamous cell carcinomas (HNSCC). Present in liver cancer cells (at protein level). Antibodies against CIP2A are present in sera from many patients with gastric or prostate cancer, suggesting that it may act as a marker for such cancers.