Survey of int region DNA rearrangements in C3H and BALB/cfC3H mouse mammary tumor system.

Rearrangement of the int-1 and int-2 regions of mouse chromosomes was compared in the C3H and BALB/cfC3H hyperplastic alveolar nodule and its hyperplastic outgrowth (HPO) model systems by examining the DNA of the different stages of the neoplastic progression, with use of the Southern blot technique. Rearrangement of int region DNAs associated with proviral amplification occurred more frequently in spontaneous tumors (19 of 27) than in tumors from HPOs (7 of 37) and rarely occurred in HPOs (1 of 29). However, the int-1 rearrangement maintained in 1 BALB/cfC3H HPO line through 11 transplant generations suggests that the int-1 rearrangement is neither sufficient nor necessary for progression to mouse mammary carcinoma.