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Analysis of calcium‐dependent protein kinase C isoforms in the early stages of diethylnitrosamine‐induced rat hepatocarcinogenesis
Author(s) -
Perletti Gian Paolo,
Piccinini Francesco,
La Porta Caterina A. M.,
Comolli Roberto
Publication year - 1993
Publication title -
molecular carcinogenesis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.254
H-Index - 97
eISSN - 1098-2744
pISSN - 0899-1987
DOI - 10.1002/mc.2940080408
Subject(s) - protein kinase c , isozyme , 2 acetylaminofluorene , alpha (finance) , gene isoform , biology , beta (programming language) , medicine , pkc alpha , endocrinology , hepatocyte , microbiology and biotechnology , carcinogenesis , enzyme , biochemistry , in vitro , microsome , gene , construct validity , nursing , computer science , programming language , patient satisfaction
Abstract The profiles of the calcium‐dependent protein kinase C (PKC) isozymes α, β, and γ were examined in subcellular fractions from Fischer 344 rat liver during the early stages (48 h, 96 h, 7 d, and 60 d) of diethylnitrosamine (DEN)‐induced carcinogenesis, using the Solt‐Farber “resistant hepatocyte” model (DEN‐2‐acetylaminofluorenepartial hepatectomy; DEN‐AAF‐PH), and then related to the presence of focal or nodular m̀‐glutamyl transpeptidase (GGT)—positive morphologic changes in the liver. After DEAE and hydroxyapatite column chromatograaphy, two peaks, immunologically identified as PKC‐α and ‐β isoforms, were detected in the liver of normal (α/β ratio=4.0) and treated rats. In DEN‐AAF‐PH hepatocarcinogenesis an increase in PKC‐α expression was found after PH ( + 43 ± 19% at 48 h, α/β ratio=5.1; + 125 ± 25% at 96 h, α/β ratio=4.8), whereas the PKC‐β isoform appeared less significantly modified (+ 11 ± 3% at 48 h and + 89 ± 17% at 96 h). Seven and 60 days after PH, a marked increase in the PKC‐α ( + 96 ± 20% and + 150 ± 48%, respectively) and PKC‐β isoforms (+ 158 ± 41%, α/β ratio=3.1 and + 130 ± 26%, α/β ratio=4.4, respectively), occurred along with the appearance of GGT‐positive altered hepatic foci and nodules in the liver sections. Sham hepatectomy caused PKC‐α and ‐β isoform activities similar to those of normal controls. In contrast, saline‐AAF‐PH‐treated rats had downregulation of PKC‐α after PH (α/β ratio=1.8 at 96 h), possibly due to the mitoinhibitory effect of the carcinogen AAF on normal uninitiated hepatocytes. Immunohistochemical analysis with monoclonal antibodies to PKC‐α and ‐β revealed diffuse positive cytoplasmic signals in GGT‐positive foci and nodules in rat liver. Taken together, these preliminary results, using the Solt‐Farber model of liver carcinogenesis, suggest a role for PKC in tumor promotion. They also suggest that the PKC‐α isoform may play a specific role in clonal expansion of DEN‐initiated hepatocytes after PH.