Aberrant Expression of CIP2A Overlapping with EGFR in Oral Cancer

A cancerous inhibitor of the tumor suppressor protein phosphatase 2A (CIP2A) has been identified recently and reported to be overexpressed in human head and neck squamous cell carcinoma and colon cancer. Objective: To determine if CIP2A has aberrant expression in oral squamous cell carcinomas using samples from a cohort of patients with five year survival data. Methods: Paraffin block samples were obtained from 25 patients diagnosed with oropharyngeal cancer. The samples included different areas within the oral cavity such as the tongue and palate, as well as from the larynx, lymph nodes, and tonsils. Four micron sections were cut, processed using antigen retrieval method, and immunostained with a rabbit anti-CIP2A serum. Rabbit pre-immune serum and rabbit anti-giantin antibodies were also used as negative and positive staining controls, respectively. The expression level of the CIP2A antigen was determined by immunofluorescence. Costaining was carried out with murine monoclonal antibody to epidermal growth factor receptor (EGFR). Results: All samples were positive with the anti-giantin antibodies indicating that the antigen retrieval method and staining protocols were successful. CIP2A expression was generally high in differentiated epithelium compared to the undifferentiated basal layer. In contrast EGFR staining was strongest in basal layers. In some tumors, no aberrant CIP2A expression was observed whereas the near-adjacent epithelium displaying dysplastic features and occasional foci of in-situ changes exhibited aberrant expression of CIP2A. Overlap elevated CIP2A expression with EGFR was clearly observed in some but not all samples. CIP2A and EGFR staining were negative in a normal human epithelial control tissue. Conclusion: CIP2A aberrant expression is present in oral squamous cell carcinomas and may be a useful cancer biomarker complementing EGFR. This research was supported by the UFCD Student Summer Research Fellowship and NIDCR grant T32 DE007200.