Factors in the Causation of Spontaneous Hepatomas in Mice

Abstract

In reciprocal F₁ hybrids between high-hepatoma C3HfB strain and low-hepatoma YBR strain, the occurrence of hepatomas was higher in those with C3HfB mothers than in those with YBR mothers, higher in males than in females, and higher in the yellow (A^VA) than in the agouti (Aa) hybrids. The maternal effect, however, was not considered as evidence of a hepatoma virus, for hepatomas did occur in progeny of YBR mothers, the highest incidence being 95% in one group. Instead it appeared that the maternal effect was nutritional. Those groups with the C3HfB mothers and the higher incidences of hepatomas had higher average weights than the comparable groups with YBR mothers. The effect of sex and genotype on occurrence of hepatomas likewise paralleled their effect on normal growth. These three pairs of factors in their various combinations resulted in variation in incidences of hepatomas ranging from 0% in agouti females with YBR mothers to 100% in yellow males with C3HfB mothers. These groups had the lowest and highest average body weights, respectively, but the range of body weights did not extend beyond what might be considered normal weight for healthy mice. It is suggested that the action of each of these three pairs of factors on influencing the occurrence of hepatomas may be related to the effect of each on normal growth.