Cytotoxic effects of methionine alkyl esters and amides in normal and neoplastic cell lines.

Homologous series of L-methionine alkyl ester hydrochlorides and tosylates were synthesized and evaluated for in vitro growth inhibitory activity in Meth A sarcoma. Cytotoxicity, as determined by [3H]thymidine incorporation, was found to be directly proportional to alkyl chain length and surface tension lowering activity. L-Methionine decyl and dodecyl ester hydrochlorides possessed optimum cytotoxic activity (IC50 = 29, 28 microM) which was not reversible by the addition of L-methionine. Surface tension of a 50 microM solution of the decyl and dodecyl ester hydrochlorides were 35.4 and 32.7 dyn/cm, respectively. The corresponding decyl and dodecyl ester tosylates and amide hydrochlorides were less active. The N-t-butoxycarbonyl analogues were essentially inactive, demonstrating the necessity of an unsubstituted and/or potentially cationic amino group. Methionine dependence characteristics and cytotoxicity were also determined for three human (IMR-90, LX-1, MCF7) and four additional murine (L1210, L5178Y, 3T3, SV-T2) cell lines. The human cell lines Meth A, LX-1, and SV-T2 were found to be methionine independent. The LX-1 tumor cell line and the SV-T2 transformed line exhibited two to four times more sensitivity to the cytotoxic and cytolytic properties of the decyl and dodecyl ester hydrochlorides than their normal counterparts. The dodecyl amide hydrochloride derivative demonstrated enhanced cytotoxic activity in vivo relative to the corresponding ester, possibly due to decreased metabolic hydrolysis.