Molecular Analysis of the Protein Tyrosine Phosphatase y Gene in Human Lung Cancer Cell Lines

The protein tyrosine phosphatase 7 (PTPy) gene has recently been suggested as a candidate tumor suppressor gene involved in the oncogenesis of human lung and renal cancers, although no direct evidence for PTPy mutations has been demonstrated thus far. We explored the status of PTPy in 31 human lung cancer cell lines as well as in various other types of human tumor cell lines. Northern blot analysis revealed that two independent cell lines expressed PTPy mRNAs with sizes distinct from those in human fetal and adult normal lung. However, our extensive search for mutations in the PTPy gene failed to identify any abnormalities in the cytoplasmic region, which contains two protein tyrosine phosphatase-like domains. These results warrant further examination of genetic alterations in the extracellular and transmembrane domains of PTPy, which had not been cloned at the rime of the present study.