Selective increase in expression of isoform PP1 gamma 1 of type-1 protein phosphatase in chondrosarcoma cells.

The expression of the two catalytic subunits of protein phosphatase (PP) type 1 PP1 gamma 1 and PP1 delta was examined in 4 cases of osteochondroma and 4 cases of enchondroma as a benign cartilaginous tumor, and 4 cases of chondrosarcoma as a malignant cartilaginous tumor using immunohistochemical analysis. The percentage of tumor cells stained positively with antiserum against PP1 catalytic subunit isoform PP1 gamma 1 were significantly higher in chondrosarcoma than in osteochondroma and enchondroma. Furthermore, chondrosarcoma showed markedly high S-phase fraction in the cell cycle of tumor cells, as compared to osteochondroma and enchondroma. These results suggest that PP1 gamma 1 is involved in the accelerated growth of malignant cells in chondrosarcoma.