Effect of core lipopolysaccharides from Salmonella minnesota R mutants on the survival times of mice bearing Ehrlich tumor.

Injection of a homologous series of bacterial core lipopolysaccharides obtained from Salmonella minnesota R mutants to Ehrlich solid tumor-beating mice results in an increase of survival times of treated animals. Lower chain length favors greater antitumor activity. Oligosaccharides and polysaccharides derived from lipopolysaccharides were found to be ineffective in increasing survial time of tumore-bearing mice. Smaller-sugar-chain-length core lipopolysaccharides were found to be better adjuvant than were those with longer sugar chains. Implication of adjuvant action of lipopolysaccharides in the elicitation of antitumor activity is suggested.