Histochemical staining of protein-tyrosine phosphatase activity in primary human mammary carcinoma: relationship with established prognostic indicators.

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Abstract
Protein-tyrosine phosphatase (PTPase) activity in frozen human mammary primary carcinoma tissue sections has been quantitated using a modified histochemical assay. The improved method features the assay of PTPase activity in 12-microns sections of air-dried unfixed tissues, and the use of [2-(N-morpholino)-ethanesulfonic acid] (MES) buffer to prepare stable reaction solutions. Tissue samples from 53 primary human mammary carcinomas were assayed for PTPase activity, and immunohistochemically stained for c-erbB-2 protein-tyrosine kinase expression. Elevated levels of PTPase activity were found in 68% of the tumors compared with the level of activity found in normal human mammary tissues. PTPase activity was co-localized with pathology definitive for carcinoma. Excessive activity was demonstrated throughout the cell, with high activity evident in the cell cytoplasmic membrane and the nucleus. Coexistence of elevated expression of c-erbB-2 and increased PTPase activity was present in 53% of the tumors. In contrast, 15% displayed low c-erbB-2 expression and high PTPase activity, and 24% displayed high c-erbB-2 expression and low PTPase activity. No statistically significant association was found between increased PTPase activity and either c-erbB-2 overexpression or grade and stage of disease in primary human mammary tumors.

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