Carcinogenesis, Vol 19, 1559-1563, Copyright © 1998 by Oxford University Press
B Lindeman, E Skarpen and HS Huitfeldt
Exposure of cells to a variety of stresses such as heat, radiation and
xenobiotics leads to increased expression of heat-shock proteins (HSPs).
HSPs protect cells against irreversible protein damage and are involved in
adaptive responses to stress stimuli. Some HSPs are overexpressed in
neoplasias, possibly contributing to the increased drug tolerance often
observed in such lesions. We have studied HSP expression in two
experimental rat hepatocarcinogenesis models. Our aim was to clarify
whether they are involved in stress adaptation in hepatocytes during
carcinogen exposure, and whether HSPs may contribute to xenobiotic
resistance in preneoplastic lesions. The complete carcinogen
2-acetylaminofluorene (AAF) was used in a continuous feeding protocol, and
in the resistant hepatocyte model where the growth of diethylnitrosamine
initiated lesions is efficiently promoted. Of the HSPs tested, only
heat-shock protein 27 (hsp27) was induced during continuous AAF exposure.
After 4 weeks of feeding AAF, increased hsp27 expression was noted in
hepatocytes in perivenous areas of the liver lobule, possibly mediating an
adaptive response to stress caused by reactive AAF metabolites. Enzyme
altered preneoplastic foci were not found to overexpress HSPs. Thus, HSP
induction does not seem to be a general mechanism underlying the increased
stress tolerance observed in such lesions.
ARTICLES
Stress protein expression in rat liver during tumour promotion: induction of heat-shock protein 27 in hepatocytes exposed to 2- acetylaminofluorene
Institute of Pathology, The National Hospital, University of Oslo, Norway. birgitte.lindeman@labmed.uio.no
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