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Transfer of Sensitivity to Tumor Promoters by Transfection of DNA from Sensitive into Insensitive Mouse JB6 Epidermal Cells

¹ Laboratory of Viral Carcinogenesis, National Cancer Institute, Frederick, Maryland 21701
² Laboratory of Experimental Pathology, National Cancer Institute, Frederick, Maryland 21701
³ Program Resources Inc., Frederick, Maryland 21701

ABSTRACT

Sensitivity to promotion of transformation by tumor promoters in mouse epidermal JB6 cells appears to have a genetic basis since the phenotypes of both promotable and nonpromotable JB6 cells derived from a common parent line are stable. Hybridization of promotable (P⁺) and nonpromotable (P^–) cells previously indicated that promotability appears to behave as a dominant trait. These results suggest that it should be possible to find DNA sequences which specify sensitivity to promotion of anchorage independence by 12-o-tetradecanoyl-phorbol-13-acetate (TPA). Cellular DNA isolated from one of two P⁺ lines, JB6 Cl 41 or JB6 Cl 22, was CaPO₄ precipitated and used to transfect the P^– cell line JB6 Cl 30. At 7 days posttransfection, the cells were suspended in agar with or without TPA at 1.6 x 10^–8 M and assayed 10 days later for TPA-dependent colony formation. Untreated or Cl 30 DNA-treated P^– JB6 Cl 30 cells yielded 40 to 50 colonies per 10⁵ cells. In contrast, transfection of Cl 30 cells with "P⁺ DNA" derived from either Cl 41 or Cl 22 yielded 200 to 500 TPA-induced colonies per 10⁵ cells, or a five- to eightfold enhancement of promotability. The enhanced promotability obtained after transfection with P⁺ DNA was stable, as judged by the retention of promotability for at least eight passages in cell lines derived from TPA-induced agar colonies. Other transfectants showed irreversible transformation by TPA, as observed in the parental P⁺ lines. When NIH 3T3 cells instead of the putative preneoplastic JB6 Cl 30 cells were used as recipients for transfection of P⁺ DNA, no evidence for acquisition of promotability was obtained. P^– JB6 Cl 25, like Cl 30, also permitted expression of transfected P⁺ DNA. These results suggest that sensitivity to phorbol ester promotion of transformation in JB6 cells is determined by DNA sequence(s) present in the P⁺ DNA and requires recipient cells of the appropriate phenotype for expression.