Cultured proliferating rat mammary epithelial cells

Abstract

Normal epithelial cells from the rat mammary gland proliferated in culture when plated with lethally irradiated cells of the LA7 rat mammary tumor line. Proliferation of the normal rat cells occurred as the LA7 cells slowly died from the radiation. By labeling the cultures with 3H-thymidine it was determined that most of the proliferating rat cells were those adjacent to the LA7 feeder cells. The epithelial cells from the primary culture proliferated after subsequent passages if the cells were plated at each subculture with newly irradiated LA7 cells. If the cells were plated at a ratio of approximately 1:8 rat:LA7 a confluent layer of normal rat cells covered the plastic substrate after 6 to 7 wk. The cells have so far been carried up through Passage 7, which amounted to approximately 19 doublings in cell number, and still proliferate vigorously. The growth medium for this culture system was Dulbecco's modified Eagle's medium:Ham's F12 1:1 supplemented with fetal bovine serum, insulin, and antibiotics. The presence in the cells of keratin, desmosomes, and cell junctions attested to their epithelial origin. The cultures were composed of cells with diploid or near diploid chromosome numbers. Samples of the cultured cells were implanted into the cleared fat pads of nude mice. Most of the implants from Passage 2 formed normal mammary ductal structures, but the incidence of outgrowths decreased significantly with later passages until no outgrowths resulted from the implantation of cells from Passage 5. The one unusual, feeder-independent cell line that arose from a primary culture seemed to be immortal in culture, contained a hyperdiploid chromosome complement, and formed abnormal structures when implanted into cleared fat pads.

An in vitro model of epithelial cell growth stimulation in the rodent mammary gland

“…Each of these modes of cell stimulation could contribute to a system that ensures replacement of a wounded cell in an epithelial sheet. That irradiated LA7 cells also support multiplication of normal mammary cells from the rat (Ehmann et al 1991), the same species from which the LA7 cell line was derived, supports this model of cell replacement. Cultured MMEC express markers of the luminal ductal population, which are thought to comprise the main proliferative population of the mammary gland.…”

Identification and Localization of Genes Which Restore Senescence in Breast Cancer Cells.

“…Two human breast adenocarcinoma cell lines, SKBR-3 and MCF.7 (American Type Culture Collections, Rockville, MD), and two rat mammary tumor cell lines NMU (American Type Culture Collections), and LA7 (Ehmann et al, 1991) All cell lines were routinely cultured in DF12 medium supplemented with 10-15% fetal bovine serum at 37° C in a 7.5% C0 2 / air atmosphere. The medium for selection and propagation of chromosome transfer clones and donor mouse/human monochromosomal hybrid cell lines contained 25 U^g/ml mycophenolic acid and 70 fi-g/ml xanthine (MX medium).…”