Inheritance of Resistance to Polyoma Tumorigenesis in Inbred Mice

Summary

The inheritance of resistance to polyoma-virus-induced tumorisenesis of C57BL/KI mice, crossbred with the tumor-susceptible DBA/2 strain, was investigated. Polyoma tumor incidences in the various animal groups inoculated neonatally with 0.05 ml of polyoma virus (hemagglutination titer 1:512) were as follows: DBA/2, 93 percent; C57BL/KI, 7 percent; (DBA/2 × C57BL/KI)F₁, 27 percent; (DBA/2 × C57BL/KI)F₂, 52 percent; F₁ × DBA/2, 75 percent; F₁ × C57BL/KI, 10 percent. The tumor incidences in F₁ and F₂ hybrids and the backcross mice support the assumption that the tumor resistance of C57BL/KI mice is an incompletely dominant characteristic of relatively simple inheritance. The figures are compatible with an inheritance depending on 2 or 3 independent genes, all of which are required for the expression of the resistance. It seems that double doses of the genes are more efficient in conferring resistance than single doses. The effects of virus dose and route of inoculation, as well as the choice of the susceptible parent strain on tumor incidence in the hybrid mice, are discussed in relation to another study in which different conclusions were reached about the inheritance of the polyoma tumor resistance in C57BL mice.