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Pre-crisis Syrian golden hamster (SGH) pancreatic duct cells were transfected with the plasmid pW2-t/B1, which encodes for a truncated SV40 large T antigen consisting of the first 119 amino acids. Transfected cells (SV) formed tumors upon s.c. injection into nu/nu mice, although with low efficiency and unusually long latency. A tumor cell line (SVT1A) was developed from the tumors and its characteristics compared to those of SV. Both cell lines were negative for mutations at codons 12 or 13 of the K-ras oncogene. No alterations in the tumor suppressor gene p53 could be detected by SSCP or immonoperoxidase techniques. The requirements for growth factors supplementation of the growth medium was investigated in the two cell lines. Both cell lines were equally dependent on the presence of insulin, transferrin, and dexamethasone, however, in contrast to SV, the tumor cell line SVT1A appeared not to require EGF for optimal growth. Sublines of SV cells could be adapted to grow in the absence of EGF. To investigate whether the acquisition of EGF independence was contributing to the tumorigenicity of SVT1A cells, sublines of SV, SV(-), adapted for various lengths of time to grow in EGF-free conditions, were tested for their ability to form tumors in nude mice. Tumorigenicity was found to correlate to the extent of adaptation of the sublines to the EGF-free medium. The SV(-) sublines, as well as SVT1A, but not SV cells, were found to produce TGF-usd\alpha .usd We speculated that the capacity to grow in the absence of exogenous EGF, as well as the increased tumorigenicity of SV(-) and SVT1A could be a consequence of the endogenous TGF-usd\alphausd production. To test this hypothesis we transfected a subclone of SV(-) obtained by soft agar cloning, with a plasmid that carries a cDNA fragment of the human TGF-usd\alphausd in the antisense orientation. Five stably transfected clones were isolated. The extent of endogenous TGF-usd\alphausd message inhibition measured in northern blots varied among the clones between 17 and 78%. The in vitro growth in medium lacking exogenous EGF was inversely related to the extent of TGF-usd\alphausd inhibition. In addition, the antisense construct appeared to suppress at least in part, the in vivo growth of transfected clones, since tumors developed later and grew slower respect to controls, after subcutaneous injection of the cells into nude mice.
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