Production of peptide growth factors by oncogene-transformed balb serum-free mouse embryo cells

Graduation date: 1989DNA from the human squamous carcinoma cell line, SK-MES-1, and the\ud plasmids, pUC EJ6.6 containing H-ras oncogene, pSVc-mycl containing\ud cellular myc gene, pNRSac containing N-ras oncogene, pBR SV containing\ud SV40 virus DNA, pSV2-neu containing neu oncogene and pSV2-neo\ud containing neomycin resistant gene were used to transform Balb serum-free\ud derived mouse embryo (Balb SFME) cells by the calcium phosphate-DNA\ud precipitation technique. Some of the transformed cell lines were tested for\ud growth rate under the serum-free condition without the epidermal growth\ud factor (EGF) and for tumorigenic activity in subcutaneously injected mice.\ud The concentrated conditioned media obtained from the oncogene-transformed\ud cell lines were analyzed by the growth stimulation assay and\ud the EGF-receptor binding competition assay.\ud The myc/H-ras-, the H-ras- and the neu-transformed Balb SFME cells\ud grew in the minus EGF serum-free condition and developed tumorigenic\ud potential; this was not true of the neo/myc-, the neo- and the\ud nontransformed-Balb SFME cells. Concentrated conditioned media from the\ud myc/H-ras- and the H-ras-transformed Balb SFME cells noticeably\ud stimulated the growth of Balb SFME cells and competed for binding to EGFreceptor\ud of Baib SFME cells. However, the neu-transformed Baib SFME cells\ud did not produce detectable amounts of type alpha-transforming growth\ud factor (TGF-alpha), showing no growth stimulation activity and no\ud competition with labeled EGF in binding to EGF-receptor. Conditioned media\ud from the N-ras-, the SV40-, and the SK-MES-1-transformed Balb SFME cells\ud stimulated the growth of Balb SFME cells in the minus EGF serum-free\ud culture, substituting for the EGF-dependence.\ud The ras oncogene-transformed cells produced TGF-alpha, which\ud produces a mitogenic response through binding to the EGF-receptor.\ud However, the neu oncogene-transformed cells failed to produce TGF-alpha,\ud but their receptor-like product autonomously produced a mitogenic signal.\ud The presence of myc oncogene, when cotransformed with ras oncogene,\ud increased the rapid growth ability of the ras oncogene-transformed cells in\ud the minus EGF serum-free culture, developing earlier tumor formation in\ud mice and producing more TGF-alpha into the conditioned media. By itself,\ud the myc oncogene failed to produce either of these effects