[Antitumor effect of Cepharanthin in the double grafted tumor system]

The antitumor effect of Cepharanthin (CR) in a new experimental mouse model was studied. Intratumoral administration of CR strongly inhibited the growth of Meth-A solid tumors in male BALB/c mice and led to a complete regression of tumors and resistance to reinoculated tumor. Subsequently, the antimetastatic effect of CR was examined in the double grafted tumor system, in which mice first received simultaneous intradermal inoculations of Meth-A in both right (10(6) cells) and left (2 x 10(5) cells) flanks and were then injected with 0.5 mg of CR in the right tumor on days 3, 4 and 5. CR inhibited the growth of not only the right but also the left, nontreated tumor. Immunized spleen cells were taken from mice which had been cured with the intratumoral administration of CR. Adoptive transfer of CR immunized spleen cells caused the complete regression of Meth-A tumors. The effector cell activity was lost only after treatment with anti-Lyt-1 antibody. These results suggest that intratumoral administration of CR might induce Lyt-1 positive cytotoxic cells in the spleen and the left, non-treated tumor. In BALB/c nude mice, CR inhibited the growth of the right tumor but did not the left tumor. Therefore, the antitumor activity of CR on the left tumor in the double grafted tumor system is associated with a sequential immune mechanism in which T cells may play an important role. The antitumor effect of CR on the right tumor is direct cytotoxic effect. TILs (tumor infiltrating lymphocytes) obtained from left and right sides tumors treated with CR were examined by Winn assay for their antitumor activity against Meth-A sarcoma in BALB/c mice. TILs from both sides clearly inhibited the growth of admixed Meth-A cells and seems to play an important role on antitumor effect in both tumors.