A new tumor promoter, dihydroteleocidin b, enhances cell growth and the production of murine leukemia virus by fibroblasts

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Abstract
The effects of tumor promoters on the expression of murine leukemia virus (MuLV) were studied in tissue culture. Dihydroteleocidin B, an indole alkaloid, recently found to be a tumor promoter, enhanced not only the production of Moloney MuLV (M‐MuLV) by a mouse fibroblast cell line, C3H2K, persistently infected with M‐MuLV, but also growth of the C3H2K cells. The production of infectious M‐MuLV by M‐MuLV‐infected C3H2K cells that had been treated with dihydroteleocidin B for 1‐7 days was four or five times higher than that of control cells. C3H2K cells grew faster and became stationary at higher cell densities in the presence of dihydroteleocidin B than in its absence. The tumor‐promoting phorbol esters phorbol‐12, 13‐didecanoate and 12‐O‐tetradecanoylphorbol‐13‐acetate also enhanced the production of M‐MuLY, but their effects were not so strong as that of dihydroteleocidin B. These tumor promoters, however, did not induce production of endogenous MuLV in C3H2K or K‐BALB cells.