Enhanced expression of catalytic subunit isoform PP1 gamma 1 of protein phosphatase type 1 in malignant fibrous histiocytoma.

The expression of the three catalytic subunits of protein phosphatase (PP) type 1 and 2A, PP1 alpha, PP1 gamma 1, and PP2AC, was examined in malignant fibrous histiocytoma using immunohistochemical analysis. The percentage of cells stained positively with antiserum against PP1 catalytic subunit isoform PP1 gamma 1 was significantly higher in tumorous region than in non-tumorous region of malignant fibrous histiocytoma. Furthermore, tumorous region showed markedly high S-phase fraction in the cell cycle, as compared to non-tumorous region. These results suggest that PP1 gamma 1 is involved in the accelerated growth of tumor cells in malignant fibrous histiocytoma.