[Antitumor Effector mechanism of plant alkaloid preparation, cepharanthin, by intratumoral administration]

The antitumor effect of biscoclaurine alkaloids, at a distant site was examined in the double grafted tumor system, in which mice 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, non-treated tumor. In order to examine the role of lymph nodes in the antitumor activity of CR, regional (axillary and inguinal) lymph nodes were resected. Since in resected mice the antitumor activity of CR against the left tumor was weakened, the regional lymph nodes have a very important role in the antitumor effect of intratumoral administration of CR at a distant site. Spleen cells prepared from CR treated mice were examined for Lyt-1, Lyt-2 and L3T4 phenotypes. The number of Lyt-1 positive lymphocytes increased in the spleen after intratumoral administration of CR. Isolated tumor cells obtained from the right tumor treated with CR and the left side tumor on day 6 were cultured for 24 h. The culture supernatants were harvested and tested for the presence of chemotactic activity for neutrophil or macrophage. Significant neutrophil chemotactic factor (NCF) activity was detected in the culture media from CR-treated right tumor tissue, and macrophage chemotactic factor (MCF) activity was detected in the culture media from left tumor tissue. CR-induced NCF was partially neutralized by treatment with anti-human IL-8 IgG, and might be murine IL-8 factor. These results suggest that intratumoral administration of CR first induces neutrophils in the right tumor, then Lyt-1 positive cells in the spleen, and subsequently induces cytotoxic macrophages in the left, non-treated tumor, thus bringing about the regression of distant tumors.