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Ornithine decarboxylase over‐expression stimulates mitogen‐activated protein kinase and anchorage‐independent growth of human breast epithelial cells
Author(s) -
Manni Andrea,
Wechter Rita,
Gilmour Susan,
Verderame Michael F.,
Mauger David,
Demers Laurence M.
Publication year - 1997
Publication title -
international journal of cancer
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.475
H-Index - 234
eISSN - 1097-0215
pISSN - 0020-7136
DOI - 10.1002/(sici)1097-0215(19970117)70:2<175::aid-ijc7>3.0.co;2-u
Subject(s) - ornithine decarboxylase , spermidine , spermine , putrescine , mapk/erk pathway , biology , kinase , polyamine , ornithine decarboxylase antizyme , cell growth , microbiology and biotechnology , medicine , endocrinology , cancer research , biochemistry , enzyme
In these experiments we tested the hypothesis that constitutive activation of polyamine(PA) biosynthesis may contribute to mammary carcinogenesis. Spontaneously immortalized normal human MCF‐10A breast epithelial cells were infected with the retroviral vector pLOSN containing a cDNA which codes for a truncated and more stable ornithine decarboxylase (ODC), the rate‐limiting enzyme in PA synthesis. Upon chronic selective pressure with α‐difluoromethyl‐ornithine (DFMO) (an irreversible inhibitor of ODC), infected MCF‐10A cells exhibited an approximately 250‐fold increase in ODC activity, which persisted despite discontinuation of DFMO. ODC‐over‐expressing MCF‐10A cells showed a modest decrease in S‐adenosylmethionine decarboxylase and an increase in spermidine/spermine N 1 ‐acetyltransferase. Analysis of cellular PA profile revealed a selective accumulation of putrescine without alterations in spermidine and spermine contents. Lesser degrees of increased ODC activity were obtained reproducibly by re‐exposing the cells to incremental small doses of DFMO. We observed a bell‐shaped dose‐related positive effect of ODC activity on clonogenicity in soft agar of MCF‐10A cells. Since anchorage‐dependent growth was actually reduced, such positive influence on this feature of transformation was not a non‐specific consequence of a growth advantage provided by ODC over‐expression. In addition, we observed a close parallelism between the dose‐dependent effects of ODC expression on clonogenicity and activity of the ERK‐2 kinase, a central element of the MAPK cascade. Our data demonstrate an interaction between PA and the MAPK signalling pathway and suggest that the latter may be involved in ODC‐induced transformation of mammary epithelial cells. Int. J. Cancer, 70:175–182, 1997. © 1997 Wiley‐Liss, Inc.