OVEREXPRESSION OF THE TYROSINE PHOSPHATASE PTP1B IS ASSOCIATED WITH HUMAN OVARIAN CARCINOMAS

OBJECTIVE: Our purpose was to determine whether protein tyrosine phosp hatase 1B is overexpressed in ovarian cancers, possibly altering the b alance of intracellular tyrosine phosphorylation. STUDY DESIGN: The ex pression of protein tyrosine phosphatase 1B was assayed in frozen sect ions from 54 human ovarian carcinomas and seven normal ovaries by immu nochemical staining with monoclonal antibody AE4-2J, which is specific for protein tyrosine phosphatase 1B. The expression of protein tyrosi ne phosphatase 1B-specific messenger ribonucleic acid in tumors was de termined by Northern analysis. The results were analyzed statistically by means of Fisher's exact test. RESULTS: Minimal staining was observ ed in normal ovarian epithelium. In contrast, 43 of 54 (79.6%) tumors displayed increased protein tyrosine phosphatase 1B expression, which is statistically associated with malignancy. Overexpression was associ ated with the expression of the p185(c-erbB-2), p170(EGFR), and p165(m CSFR) growth factor receptor protein tyrosine kinases. Protein tyrosin e phosphatase 1B messenger ribonucleic acid expression was inconsisten tly increased in tumor cells. CONCLUSION: Increased expression of prot ein tyrosine phosphatase 1B in ovarian cancers that also express prote in tyrosine kinases suggests that protein tyrosine phosphatase 1B may play a role in the growth regulation of ovarian cancers.