Pregnancy dependence of mammary tumours in DDD mice congenic for Mtv-2, DDD/1-Mtv-2/Mtv-2.
Mammary tumours developed in 110 (95.7%) of 115 DDD/1-Mtv-2/Mtv-2 (DDD/1-Mtv-2) and 24 (47.1%) of 51 DDD/1fDDD/1-Mtv-2 (DDD/1fMtv-2) force-bred female mice during a one-year period. The mean tumour age +/- SE was 220 +/- 7 and 269 +/- 7 days, respectively. These tumours were examined for responsiveness to pregnancies by comparing their growth after transplantation between virgin and breeding recipients. Of 73 tumours from DDD/1-Mtv-2 mice, 9 (12%) were completely pregnancy-dependent (CPD), 3 (4%) pregnancy-dependent (PD), 9 (12%) pregnancy-responsive (PR), and 52 (71%) pregnancy-independent (PI), and of 25 tumours from DDD/1fMtv-2 mice, one (4%) was CPD, one (4%) PR, and 23 (92%) PI. Although most tumours were heterogeneous in morphology and there was no clear relation between morphology and PD properties, most CPD tumours were type P and considered to be connected with mammary plaques. When 9 CPD tumours from DDD/1-Mtv-2 mice were serially transplanted in breeders, 6, 2 and one progressed to lose pregnancy dependence within 3, 8 and 18 generations, respectively. DDD/1-Mtv-2 mice will provide a model for studies on progression of mammary tumours from hormone-dependent to autonomous states.
Sayama
K
K
Laboratory of General Biology, Meijigakuin University, Yokohama, Japan.
Kaneko
T
T
Matsuzawa
A
A
D000818:Animals; D005260:Female; D008325:Mammary Neoplasms, Experimental / Q000382:microbiology* / Q000473:pathology; D008324:Mammary Tumor Virus, Mouse / Q000235:genetics*; D051379:Mice; D009368:Neoplasm Transplantation; D011247:Pregnancy; D011270:Pregnancy, Animal