|Abstract or Summary
- DNA from the human squamous carcinoma cell line, SK-MES-1, and the
plasmids, pUC EJ6.6 containing H-ras oncogene, pSVc-mycl containing
cellular myc gene, pNRSac containing N-ras oncogene, pBR SV containing
SV40 virus DNA, pSV2-neu containing neu oncogene and pSV2-neo
containing neomycin resistant gene were used to transform Balb serum-free
derived mouse embryo (Balb SFME) cells by the calcium phosphate-DNA
precipitation technique. Some of the transformed cell lines were tested for
growth rate under the serum-free condition without the epidermal growth
factor (EGF) and for tumorigenic activity in subcutaneously injected mice.
The concentrated conditioned media obtained from the oncogene-transformed
cell lines were analyzed by the growth stimulation assay and
the EGF-receptor binding competition assay.
The myc/H-ras-, the H-ras- and the neu-transformed Balb SFME cells
grew in the minus EGF serum-free condition and developed tumorigenic
potential; this was not true of the neo/myc-, the neo- and the
nontransformed-Balb SFME cells. Concentrated conditioned media from the
myc/H-ras- and the H-ras-transformed Balb SFME cells noticeably
stimulated the growth of Balb SFME cells and competed for binding to EGFreceptor
of Baib SFME cells. However, the neu-transformed Baib SFME cells
did not produce detectable amounts of type alpha-transforming growth
factor (TGF-alpha), showing no growth stimulation activity and no
competition with labeled EGF in binding to EGF-receptor. Conditioned media
from the N-ras-, the SV40-, and the SK-MES-1-transformed Balb SFME cells
stimulated the growth of Balb SFME cells in the minus EGF serum-free
culture, substituting for the EGF-dependence.
The ras oncogene-transformed cells produced TGF-alpha, which
produces a mitogenic response through binding to the EGF-receptor.
However, the neu oncogene-transformed cells failed to produce TGF-alpha,
but their receptor-like product autonomously produced a mitogenic signal.
The presence of myc oncogene, when cotransformed with ras oncogene,
increased the rapid growth ability of the ras oncogene-transformed cells in
the minus EGF serum-free culture, developing earlier tumor formation in
mice and producing more TGF-alpha into the conditioned media. By itself,
the myc oncogene failed to produce either of these effects.