TY - JOUR
T1 - Ornithine decarboxylase over-expression stimulates mitogen-activated protein kinase and anchorage-independent growth of human breast epithelial cells
AU - Manni, Andrea
AU - Wechter, Rita
AU - Gilmour, Susan
AU - Verderame', Michael F.
AU - Mauger, David
AU - Demers, Laurence M.
PY - 1997
Y1 - 1997
N2 - 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-difluoromethylornithine (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 N1-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.
AB - 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-difluoromethylornithine (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 N1-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.
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U2 - 10.1002/(SICI)1097-0215(19970117)70:2<175::AID-IJC7>3.0.CO;2-U
DO - 10.1002/(SICI)1097-0215(19970117)70:2<175::AID-IJC7>3.0.CO;2-U
M3 - Article
C2 - 9009157
AN - SCOPUS:0031019072
SN - 0020-7136
VL - 70
SP - 175
EP - 182
JO - International Journal of Cancer
JF - International Journal of Cancer
IS - 2
ER -