Effects of two pyridinalalkyliminerhodium(I) complexes in mice bearing MCa mammary carcinoma.

The examination of the differential effects of two square-planar rhodium(I) complexes on primary tumor growth and on the formation of spontaneous and artificially (i.v. tumor injection) induced lung metastases of MCa mammary carcinoma suggests different mechanisms of action, depending on the chemical characteristics of the compound used. Of the two complexes used, cyclooctadiene(2-pyridinalmethylimine)Rh(I) chloride and cyclooctadiene(2-pyridinalisopropylimine)Rh(I) chloride, the former compound confirmed the antineoplastic action previously shown in the Lewis lung carcinoma model. The activity of this derivative on lung metastasis formation seems to be unrelated to a cytotoxic action for tumor cells localized in the lungs. More likely, it appears that modifications occurring at the primary tumor level, probably different from a tumor-cell-directed lethality, are responsible for the reduction of spontaneous lung metastasis formation observed in treated animals. The hyperplasia of the spleen induced in treated animals seems to suggest that this compound is endowed with properties typical for biological response modifiers.