Immunological studies on the antitumor effect of sporamycin.

The role of immunological effects in the antitumor activity of sporamycin activity of sporamycin was studied mainly using the mouse syngeneic tumor, Meth-A. Sporamycin inhibited the growth of the Meth-A tumor and Balb/c mice, and 12 out of 19 mice were cured. The 12 survivors did not show any growth of reinoculated Meth-A cells. Enzymes-histochemical observations revealed marked activities of both acid phosphatase and alpha-naphthyl acetate esterase in lymphoid cells and macrophages which heavily infiltrated the tumor tissue. Pretreatment of mice with sporamycin produced a remarkable inhibition of tumor growth. A marked neutralization activity against tumor cells was observed by Winn's method using spleen cell of tumor-bearing mice which had been pre- or post-treated with sporamycin. However, this neutralization activity was depressed by anti-Thy 1.2 serum plus complement. The response of spleen cells to concanavalin A was increased by treatment with sporamycin in mice. All of these findings suggest that sporamycin may, at least partially, act by modulating the cellular immune response.