RECEPTOR PROTEIN-TYROSINE PHOSPHATASE-GAMMA IS A CANDIDATE TUMOR SUPPRESSOR GENE AT HUMAN-CHROMOSOME REGION 3P21

PTPG, the gene for protein-tyrosine phosphatase-gamma (PTP-gamma), maps to a region of human chromosome 3, 3p21, that is frequently deleted in renal cell carcinoma and lung carcinoma. One of the functions of protein-tyrosine phosphatases is to reverse the effect of protein-tyrosine kinases, many of which are oncogenes, suggesting that some protein-tyrosine phosphatase genes may act as tumor suppressor genes. A hallmark of tumor suppressor genes is that they are deleted in tumors in which their inactivation contributes to the malignant phenotype. In this study, one PTP-gamma allele was lost in 3 of 5 renal carcinoma cell lines and 5 of 10 lung carcinoma tumor samples tested. Importantly, one PTP-gamma allele was lost in three lung tumors that had not lost flanking loci. PTP-gamma mRNA was expressed in kidney cell lines and lung cell lines but not expressed in several hematopoietic cell lines tested. Thus, the PTP-gamma gene has characteristics that suggest it as a candidate tumor suppressor gene at 3p21.