Bacterial proteinaceous products (bacteriocins) as cytotoxic agents of neoplasia.

Several bacteriocins, bacterial proteinaceous antibiotics, are shown to markedly inhibit the division of various established (neoplastic) mammalian cell lines. The bacteriocins tested originated from Escherichia coli, Pseudomonas aeruginosa, Vibrio cholerae, and Vibrio eltor. Using exponentially growing L60T mouse fibroblasts, the inhibitory effect was concentration dependent, and a growth inhibitory unit, equivalent to cytotoxic index 50, was established. Expression of toxicity as a function of duration of exposure to pyocin required 3 to 4 hr. DNA synthesis was inhibited and reflected the effects on growth inhibition. Maximal sensitivity to the bacteriocin was observed prior to mitosis in the G2 phase of the cell cycle.