Antitumor effect of a baker's yeast mannan-mitomycin C conjugate against mouse hepatoma, MH134, in vivo and in vitro.

A conjugate of mitomycin C and the mannan of bakers' yeast (Saccharomyces cerevisiae wild type strain) was synthesized. Assay of its growth inhibitory effect on MH134 hepatoma solid tumor implanted in C3H/He slc mice showed that this conjugate exhibited a higher growth-inhibition ratio than those of free mitomycin C and the same bakers' yeast mannan in the corresponding effective doses. This conjugate was also found to kill the same hepatoma cells in vitro. Because a dextran-mitomycin C conjugate did not manifest any antitumor effect against this tumor, it was postulated that interaction of the mannan moiety in the mannan-mitomycin C conjugate with the mannose receptor located on the cell surface of immunocytes and/or with hepatoma cells participated in the common initiating reaction of in vitro and in vivo antitumor effects.