Inhibition of Ehrlich ascites tumor cell growth by Griffonia simplicifolia I lectin in vivo.

Griffonia (Bandeiraea) simplicifolia I (GS I) seeds contain a family of alpha-D-galactopyranosyl-binding isolectins which strongly agglutinate Ehrlich ascites tumor cells due to the presence of this determinant sugar on their cell surface glycoproteins. Administration of GS I lectin (100 micrograms/day or 300 micrograms on alternate days, i.p.) inhibits the growth of Ehrlich tumor cells in vivo. Mice given injections of only Ehrlich cells lived an average of 36 +/- 13 (S.E.) days with no mouse surviving longer than 53 days. Mice given injections of Ehrlich cells and 100 micrograms GS I lectin daily or 300 micrograms GS I lectin on alternate days showed 75 and 62% survival, respectively, after 60 days. Lectin-dependent, macrophage-mediated tumor cell lysis may be the mechanism whereby the GS I lectin exerts its cytotoxic effect.