Metastatic Potential of SK-Br-3 Cells Treated with L-Cysteine or Ascorbic Acid

L-cysteine and ascorbic acid, which had previously been shown to inhibit the carcinogenic effects of tobacco and marihuana smoke on hamster and human lung cultures by interfering with the SH-reactive components of the gas vapor phase of the smoke (Leuchtenberger and Leuchtenberger, 1977), were found to modify the morphology and to enhance the growth rate of a human mammary carcinoma cell line (SK-Br-3 (Leuchtenberger and Ozzello, submitted for publication). When these cells were grc in media enriched with L-cysteine they underwent a progressive fibroblast-like transformation indicative of cellular dedifferentiation. This transformation persisted after the modified cells were returned to the original (cysteine-free) medi um. On the other hand, ascorbic acid favored the in vitro differentiation of SK-Br-3 cells which became uniformly smaller and tended to arrange themselves in rosette-like patterns. When ascorbic acid was withdrawn from the medium, the cells gradually became dedifferentiated and resembled those modified by L-cysteine.