CIP2A is a human oncoprotein that inhibits PP2A and stabilizes c-myc in human malignancies. Autoantibodies to CIP2A protein have been reported to be present in higher levels in sera from patients with hepatocellular carcinoma (HCC) than in sera of healthy individuals. The CIP2A gene has been demonstrated as a potential cancer susceptibility gene. To elucidate whether common CIP2A variants are associated with HCC susceptibility, we conducted a case-control study comprising 233 cases of HCC and 280 controls matched on age, gender and ethnicity in the Chinese Han population. Two haplotype-tagging single nucleotide polymorphisms (htSNPs) (rs2278911 and rs4855656) from the HapMap database were analyzed, which provide an almost complete coverage of the genetic variations in the CIP2A gene. We found that neither of these htSNPs and haplotypes were associated with the risk of HCC. However, an interaction was observed between hepatitis virus B and C infection (HBV and HCV) and the C carriers (TC or CC) of rs2278911 on HCC risk (OR=12.35; 95% CI, 4.93-19.87). No such association was found for rs4855656. Our study also demonstrated that two htSNPs (rs2278911 and rs4855656) in the CIP2A gene are not associated with the risk of HCC. HBV and HCV infection was found to exert a synergistic effect on the risk of HCC in individuals with the C carriers (TC or CC) of rs2278911 in the Chinese Han population.
"The wild-type has a positively charged area around Arg229 with a small inward protruding cavity next to Arg229 (Fig. 7A) whereas the corresponding area is considerably less charged in the Arg229Gln mutant and the inward protruding cavity is bigger (Fig. 7B). Coupling these results to the conclusions drawn by Li et al., 2012 suggests that the positive charge and shape of this surface area are important for the expression and function of CIP2A, and this area is possibly involved in the protein–protein complexes formed between CIP2A and other proteins, for example other oncoproteins. "
[Show abstract][Hide abstract] ABSTRACT: Cancerous Inhibitor of Protein Phosphatase 2A (CIP2A) is a human oncoprotein, which exerts its cancer-promoting function through interaction with other proteins, for example Protein Phosphatase 2A (PP2A) and MYC. The lack of structural information for CIP2A significantly prevents the design of anti-cancer therapeutics targeting this protein. In an attempt to counteract this fact, we modeled the three-dimensional structure of the N-terminal domain (CIP2A-ArmRP), analyzed key areas and amino acids, and coupled the results to the existing literature. The model reliably shows a stable armadillo repeat fold with a positively charged groove. The fact that this conserved groove highly likely binds peptides is corroborated by the presence of a conserved polar ladder, which is essential for the proper peptide-binding mode of armadillo repeat proteins and, according to our results, several known CIP2A interaction partners appropriately possess an ArmRP-binding consensus motif. Moreover, we show that Arg229Gln, which has been linked to the development of cancer, causes a significant change in charge and surface properties of CIP2A-ArmRP. In conclusion, our results reveal that CIP2A-ArmRP shares the typical fold, protein-protein interaction site and interaction patterns with other natural armadillo proteins and that, presumably, several interaction partners bind into the central groove of the modeled CIP2A-ArmRP. By providing essential structural characteristics of CIP2A, the present study significantly increases our knowledge on how CIP2A interacts with other proteins in cancer progression and how to develop new therapeutics targeting CIP2A.
[Show abstract][Hide abstract] ABSTRACT: Oncoprotein CIP2A a Cancerous Inhibitor of PP2A forms an "oncogenic nexus" by virtue of its control on PP2A and MYC stabilization in cancer cells. The expression and prognostic function of CIP2A in different solid tumors including colorectal carcinoma, head and neck cancers, gastric cancers, lung carcinoma, cholangiocarcinoma, esophageal cancers, pancreatic carcinoma, brain cancers, breast carcinoma, bladder cancers, ovarian carcinoma, renal cell carcinomas, tongue cancers, cervical carcinoma, prostate cancers, and oral carcinoma as well as a number of hematological malignancies are just beginning to emerge. Herein, we reviewed the recent progress in our understanding of (1) how an "oncogenic nexus" of CIP2A participates in the tumorigenic transformation of cells and (2) how we can prospect/view the clinical relevance of CIP2A in the context of cancer therapy. The review will try to understand the role of CIP2A (a) as a biomarker in cancers and evaluate the prognostic value of CIP2A in different cancers (b) as a therapeutic target in cancers and (c) in drug response and developing chemo-resistance in cancers.
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