Antineoplastic activity of poly(L-lysine) with some ascites tumor cells.

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Abstract
Poly(L-lysine) can be a very effective agent in preventing the growth of Ehrlich ascites tumors in mice. When given optimal doses of poly(L-lysine) (MW 60 .times. 103) i.p. for 5 consecutive days, beginning on day 1 after inoculation with Ehrlich ascites cells, White Swiss mice show nearly a 100% remission from subsequent tumor growth. Rechallenge of cured animals with tumor cells, however, shows no long-term immunological protection. In tissue culture, poly(L-Lysine) shows a related potent cytotoxicity with [human cervical carcinoma] HeLa cells; the D isomer has properties strikingly different from those of the L-isomer. In addition, there is a strong MW dependence in that the small polylysines (MW 3 .times. 103) possess less than 1/20th the cytotoxicity of large polymers (MW 70 .times. 103) on a weight basis in both cell culture and animal studies. At the same time, none of these lysine polymers gives any significant increase in life span to BDF1 mice infected with L1210 murine leukemia cells. The mechanism was explored by which the polylysines express their cytotoxicity. Lysine polymers apparently show cell specificity in their action and in some cases they may be beneficial as potent antineoplastic agents, particularly when MW is taken into consideration.