ROLE OF PROTEIN PHOSPHATASE IN MALIGNANT OSTEOGENIC AND SOFT-TISSUE TUMORS

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 osteogenic tumors and soft tissue tumors by immunohistochemical analy sis. The percentage of cells stained positively with antiserum against PP1 catalytic subunit isoform PP1 gamma 1,was significantly higher in malignant osteogenic tumors (chondrosarcoma, osteosarcoma, and Ewing' s sarcoma) and in malignant soft tissue tumors (liposarcoma and malign ant fibrous histiocytoma [M.F.H.]) than in benign tumors (osteochondro ma, osteoblastoma, ossifying fibroma, enchondroma and lipoma). Further more, the malignant tumor lesions showed a markedly high number of cel ls in the S-phase fraction of the cell cycle, as compared to benign tu mors. These results suggest that PP1 gamma 1 is involved in the accele rated growth of malignant tumor cells.