Long-term survival of adult mouse mammary glands in culture and their response to a retinoid
Telang, N.T.; Sarkar, N.H.
Cancer Research 43(10): 4891-4900
1983
ISSN/ISBN: 0008-5472 PMID: 6224553 Document Number: 203764
Previous studies have shown that the development of mammary alveolar lesions (MAL) precedes the emergence of overt mammary tumors in high-breast-cancer strains of mice, such as RIII, that are infected with exogenous murine mammary tumor virus. MAL-containing whole mammary glands from 7-mo.-old nulliparous RIII mice were cultured for 8 days (days 0-8) in a serum-free medium that contained insulin and a combination of lactogenic hormones, prolactin, aldosterone and hydrocortisone. On the 9th day, the cultures were washed, and the glands were maintained in a medium containing insulin alone for the next 14 days (days 9-23). Lobuloalveolar structures (LA) developed in the cultured glands during the 8-day period, but, during the next 14 days, in the absence of lactogenic hormones, the LA that developed during the first 8 days of culture regressed. The MAL that were present in the mammary glands before culturing remained unaltered. The survival of MAL apparently is not dependent on the lactogenic hormones, but the maintenance of LA requires these hormones. Organ cultures of MAL-free mammary glands from C57BL mice (a low-breast-cancer strain that lacks exogenous murine mammary tumor virus) maintained in the presence of the lactogenic hormones developed LA similar to those observed in the RIII cultures. Subsequent cultivation of C57BL glands in lactogenic hormone-free medium exhibited regression of LA as in the RIII cultures, and these cultured glands contained a few MAL-like structures. To evaluate the effects of retinoids on MAL, RIII mammary gland organ cultures containing MAL that had developed in vivo were incubated for days 0-8 in the presence of lactogenic hormones and were then continuously exposed to 5-10 .mu.M N-(4-hydroxyphenyl)retinamide (HPR) in lactogenic hormone-free medium for days 9-23. There was a 60-70% reduction in the number of MAL in the glands that were exposed to HPR. A 72% reduction in the number of MAL was observed in glands exposed to 5 .mu.M HPR during the entire culture period. The growth and/or maintenance of LA in mammary gland cultures from both RIII and C57BL mice that were exposed to HPR during the developmental phase of LA in lactogenic hormone-containing medium was not impaired, suggesting that HPR may preferentially induce the regression of MAL. The experiments with organ cultures of MAL-bearing adult mouse mammary glands indicate that these cultures could be an appropriate in vitro system for the study of the direct effects of antineoplastic agents and mechanism(s) of their action of mouse mammary preneoplasia.