Action of Compounds Related to Cysteine on the Regression of Jensen's Rat Sarcoma

Abstract

Since the report 1 of the effect of cysteine hydrochloride on Jensen's sarcoma in rats, attempts have been made to determine the active portion of the cysteine structure responsible for the tumor regressing action. This has been studied by injecting into the tissue of the Jensen rat sarcoma several acids with the same pH as the cysteine hydrochloride solutions, fractions of the cysteine molecule, and compounds built up from the cysteine molecule.

In the first group, hydrochloric acid, sulphuric acid, and acetic acid were tried, and also because of its sulphur content rather than acid properties, sodium thiosulphate. The acids were adjusted to the same pH as the solutions of cysteine hydrochloride and were injected in equivalent volumes. All the acids were rapidly absorbed from the tumor tissue. Except for a little central hyperemia in the tumor and occasionally a small focus of necrosis in the center of the tumor mass, no cytological changes were noted. There was no influence apparent upon the tumor growth. In the case of sodium thiosulphate no effect whatever was noted.

Because of the similarity between cysteine and alanine, the latter was injected directly into tumor tissue in dosages equivalent to the effective cysteine dose. Since the alanine formula is identical with cysteine, excepting for the removal of the S-H radical, it was felt that any differences in effect might be ascribed to the sulfhydryl group. Whereas 50 mg. of cysteine hydrochloride in 1 cc. of water causes early necrosis and often complete regression of a sarcoma nodule 2.0 cm. in diameter, a similar dose or double the dose of alanine has no effect. In fact, 200 mg. of alanine were tried daily for 5 days in the same tumor and no appreciable effect was noted either upon the tumor or upon the host.