THE CHARACTERISTIC GENE EXPRESSIONS OF MAPK PHOSPHATASE-1 AND PHOSPHATASE-2 IN HEPATOCARCINOGENESIS, RAT ASCITES HEPATOMA-CELLS, AND REGENERATING RAT-LIVER

mRNA levels of mitogen-activated protein kinase phosphatases, MKP-1 an d MKP-2, mere determined during chemical hepatocarcinogenesis and duri ng regeneration of rat liver, In chemical hepatocarcinogenesis, the mR NA levels of MKP-1 were increased in primary hepatomas but decreased i n rat ascites hepatomas. as compared with normal liver. MKP-2 was unde tectable in normal liver but strongly expressed ill hepatomas, The MKP -2 mRNA level was increased with expression of malignant phenotypes in hepatomas. In regenerating liver, the mRNA level of MKP-1 increased i mmediately but transiently after partial hepatectomy, and peaked again on day 10, the time when hepatocytes cease proliferation, The elevate d expression of MKP-1 on day 10 suggests some roles of MKP-1 as a nega tive regulator in hepatocyte proliferation. (C) 1997 Academic Press.