TRANSFORMATION OF HUMAN-CELLS BY RECOMBINANT-DNA MOLECULES CONTAINING BK VIRUS EARLY REGION AND THE HUMAN ACTIVATED C-H-RAS OR C-MYC ONCOGENES

Normal diploid human embryonic fibroblasts (HEF), human embryo kidney (HEK) cells and HEK cells from a fetus with Turner's syndrome (HEK-T) were transformed by recombinant DNA molecules containing BK virus (BKV) early region gene and either c-ras or c-myc human oncogenes: activated c-H-ras (pBK/c-rasA), normal c-H-ras (pBK/c-rasN), normal c-myc (pBK/c-myc4), rearranged c-myc from the Burkitt lymphoma cell live CA46 (pBK/c-myc5), truncated c-myc (pBK/c-myc17) obtained by removing the first non-coding exon from normal c-myc and truncated c-myc from the rearranged c-myc gene in CA46 cells (pBK/c-myc14). Transfected DNA sequences were found mostly free, in an episomal state. Specific c-H-ras, c-myc and BKV transcripts as well as c-H-ras p21 and BKV T antigen were detected in transformed cells. The recombinant DNAs had a greater transforming ability and converted cells to a more definite transformed phenotype than the single genes transfected separately, suggesting a cooperation of different functions in transformation of human cells. pBK/c-rasA was significantly more powerful than pBK/c-rasN in conferring on cells all the characteristics of transformation. After transfection with all the recombinants, normal HEF and HEK were not immortalized and did not produce tumors in nude mice. In contrast, HEK-T cells acquired an indefinite lifespan and were oncogenic in nude mice. Among pBK/c-myc recombinants, pBK/c-myc14 produced the most malignant phenotype, likely due to mutations favoring tumor progression in a conserved region of the CA46 c-myc gene. Karyotypic analysis showed several chromosomal alterations that may be related to the appearance of the transformed phenotype. The different response to transformation of normal diploid human fibroblasts and HEK-T cells from Turner's syndrome is discussed in terms of a possible loss of tumor suppressor genes in human cells with the X0 genotype.