Mammary Tumors in BALB/cfC3H and BALB/cfRIII Virgin Female Mice Bearing Hypophyseal Isografts

Abstract

The behavior and morphology of mouse mammary tumors in high cancer strain mice are controlled by the causative murine mammary tumor viruses (MuMTV). However, relationships also exist between mammary tumors and other factors such as host genotype, other etiologic agents (chemicals, X-rays), and hormones. Among the latter, prolactin has been particularly studied. The aim of this investigation was to test whether the mammary tumor morphology controlled by C3H and RIII MuMTVs is in any way influenced by continuous prolactin secretion. A total of 28 BALB/cfC3H and 24 BALB/cfRIII virgin female mice was implanted with 2 hypophyseal isografts under the kidney capsule. Mice were of the same BALB/c genotype and carried respectively C3H and RIII MuMTV infection. The biologic and morphologic characterization of the tumors observed showed that several differences previously reported between mammary tumors in breeding female mice of the 2 strains persisted in virgins bearing hypophyseal isografts. These data confirm that the mammary tumor characters in high cancer strain mice are mainly carried out and controlled by the causative MuMTVs but also suggest that different MuMTVs may show different sensitivity to continuous prolactin secretion.