MALIGNANT CONVERSION OF CHEMICALLY TRANSFORMED NORMAL HUMAN-CELLS

Two structurally unrelated chemicals, aflatoxin B-1 and propane sulton e, transformed human foreskin cells to a stage of anchorage-independen t growth. Isolation from agar and repopulation in monolayer culture of these transformed cells was followed by transfection with a cDNA libr ary, which resulted in cells that exhibited an altered epithelioid mor phology. Chemically transformed/nontransfected cells and transfected n ormal cells did not undergo a significant morphological change. These epithelioid-appearing, transfected cells, when inoculated into nude mi ce, form progressively growing tumors. The tumors are histopathologica lly interpreted as carcinomas. All of the first generation tumors in t he surrogate hosts exhibited characteristic rates of growth similar to those of transplants of spontaneous human tumors. In the second gener ation of tumor xenografts, the progressively growing tumors derived fr om the transfected cells exhibited a more rapid rate of growth. Southe rn analysis and reverse transcription PCR confirmed that a 1.3-kb gene tic element was integrated into the genome and was actively being tran scribed. Examination of the metaphase chromosomes in normal human cell s revealed that the genetic element responsible for this conversion wa s located at site 31-32 of the q arm of chromosome 7. The DNA sequence of this 1.3-kb genetic element contains a coding region for 79 amino acids and a long 3'-untranslated region and appears to be identical to CATR1.3 isolated from tumors produced by methyl methanesulfonate-conv erted, nontransplantable human tumor cells.