PATERNAL TRANSMISSION OF MAMMARY TUMOR VIRUS FROM DD/Tbr STRAIN OF MICE BY CROSSING WITH BALB/c OR C57BL/6J STRAINS

Abstract

Paternal transmission of mammary tumor virus (MTV) was revealed by the crosses between high mammary-cancer DD/Tbr and low mammary-cancer BALB/c or C57BL/6J strains of mice. The DD/Tbr strain of mice developed mammary tumors with 77.7% incidence at an average tumor age of 9.3 months in F₄₄ to F₅₆ generations. The hybrid mice between DD/Tbr (D) and BALB/c (C) developed mammary tumors with identical incidence in both reciprocal crosses; 66.7% incidence at an average age of 16.4 months in DCF₁ and CDF₁. In the hybrids between DD/Tbr (D) and C57BL/6J (B), an incidence of mammary tumor was 90.8% in DBF₁ and 84.2% in BDF₁ at an average tumor age of 8.7 months and 8.9 months, respectively. The DD/Tbr-MTV was more susceptible to the hybrid mice between D and B than to those between D and C. Mammary tumors from these hybrid mice demonstrated type B particles, suggesting that the DD/Tbr-MTV was transmitted by either maternal or paternal route. Plaque-inducing ability and paternal transmission are specific for DD/Tbr and GR strains, but the mammary tumor age in DD/Tbr strain is not so young as in the GR strain which carries MTV-P. RIII strain has a plaque-inducing ability, but fails to transmit its MTV (MTV-PS) by paternal route. Therefore, DD/Tbr-MTV has intermediate characteristics between MTV-P and MTV-PS.