Altered distribution and expression of protein tyrosine phosphatases in normal human skin as compared to squamous cell carcinomas.

Amounts and subcellular localizations of 4 protein tyrosine phosphatases (PTPs) were compared in cultured normal human keratinocytes, an immortalized keratinocyte cell line, and 2 squamous cell carcinoma (SCC) lines. Cellular localizations for PTPs were determined in biopsies of normal human skin and SCCs. Compared to normal keratinocytes, SCC cell lines had higher levels of PTP-1B and T-cell PTP and comparable levels of PTP-1C or PTP-1D. The subcellular localization of each PTP was similar in the 3 types of keratinocytes with PTP-1B localizing to the endoplasmic reticulum, T-cell PTP exclusively found in the nucleus, PTP-1C localized to the plasma membrane, cytosol and nucleus, and PTP-1D present in both cytosol and nucleus. Compared to normal skin, immunoreactive PTP-1B was markedly increased in the invasive margins of SCCs while T-cell PTP was generally increased in tumors. PTP-1C immunostaining varied between cells with no obvious difference between normal and neoplastic tissues. The intensity and distribution of immunoreactive PTP-1D varied greatly between cells within tumors. These differences in amounts and in cellular and subcellular localization of these PTPs, especially those differences in invasive margins of SCCs, may reflect the diverse roles these PTPs play in the proliferation and invasive potential of neoplastic keratinocytes.