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Mol. Cell. Biol., 03 1996, 884-891, Vol 16, No. 3
GM D'Abaco, RH Whitehead and AW Burgess
Colon carcinomas appear to arise from the cumulative effect of mutations to
several genes (APC, DCC, p53, ras, hMLH1, and hMSH2). By using novel
colonic epithelial cell lines derived from the Immorto mouse, named the
YAMC (young adult mouse colon) cell line, and an Immorto-Min mouse hybrid,
named the IMCE (Immorto-Min colonic epithelial) cell line, carrying the Apc
min mutation, we investigated the effect of an activated v-Ha-ras gene on
tumor progression. The YAMC and IMCE cell lines are normal colonic
epithelial cell lines which are conditionally immortalized by virtue of
expression of a temperature- sensitive simian virus 40 (SV40) large T
antigen. Under conditions which permit expression of a functional SV40
large T antigen (33 degrees C plus gamma interferon), neither the YAMC nor
the IMCE cell line grows in soft agar or is tumorigenic in nude mice. In
vitro, when the SV40 large T antigen is inactivated (39 degrees C without
gamma interferon), the cells stop proliferating and die. By infecting the
YAMC and IMCE cell lines with a replication-defective psi2-v-Ha-ras virus,
we derived cell lines which overexpress the v-Ha-ras gene (YAMC- Ras and
IMCE-Ras). In contrast to the parental cell lines, under conditions in
which the SV40 large T antigen is inactive, both the YAMC- Ras and IMCE-Ras
cell lines continue to proliferate. Initally YAMC-Ras cells do not form
tumors; however, tumors are visible after 90 days of incubation. IMCE-Ras
cells form colonies in soft agar under both permissive and nonpermissive
culture conditions. Furthermore, IMCE-Ras cells form tumors in nude mice
within 3 weeks. The phenotype of the IMCE-Ras cell line thus clearly
demonstrates that a defective Apc allele and an activated ras gene are
sufficient to transform normal colonic epithelial cells and render them
tumorigenic.
Copyright © 1996, American Society for Microbiology
Synergy between Apc min and an activated ras mutation is sufficient to induce colon carcinomas
Melbourne Tumour Biology Branch, Ludwig Institute for Cancer Research, Victoria, Australia.
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