Lectin potentiation of BCG-contact-mediated antitumor action.

Concanavalin A (Con A) potentiated the BCG-contact-mediated antitumor action when both Con A (10 microgram) and BCG (50 micrograms) were injected with fibrosarcoma cells (5 x 10(4)) into inbred Swiss mice. BCG (50 micrograms) alone had no antitumor effect. The Con A-potentiated BCG-contact-mediated phenomenon was shown to be immunologically mediated, inasmuch as tumors developed in immunosuppressed mice inoculated with tumor cells mixed with Con A and BCG. The same dose of 50 micrograms BCG was effective in controlling the growth of 10(6) fibrosarcoma cells in the presence of Con A. The specific inhibitor of Con A, alpha-methyl D-mannoside, abrogated the potentiation of the BCG effect seen with Con A. Con A also increased the antitumor effect of BCG in sarcoma 180 ascites tumor. Another lectin, peanut agglutinin, also induced an antitumor effect in the presence of BCG only when the tumor cells were treated with Vibrio cholerae neuraminidase.