ESTABLISHMENT OF HORMONE-DEPENDENT AND HORMONE-INDEPENDENT CARCINOMA CELL-LINES WITH DIFFERENT METASTATIC POTENTIALS FROM SPONTANEOUS MAMMARY-TUMORS IN AGED WISTAR RATS

Three stable carcinoma cell lines, designated RM22-F5, RM17-5R, and RM 1-4, were established from spontaneously occurring mammary carcinomas in old, outbred, female Wistar rats. The RM22-F5 and RM17-5R cells wer e keratin-positive and formed epithelial monolayers, whereas RM1-4 cel ls exhibited a spindlelike morphology and intense vimentin staining. W hen injected into nude mice, RM22-F5, RM17-5R and RM1-4 cells formed w ell differentiated, poorly differentiated and undifferentiated carcino mas, respectively. The relative growth rates of the tumor cells in vit ro were RM1-4 > RM22-F5 > RM17-5R. The growth of RM22-F5, but not of R M17-5R and RM1-4 cells, was significantly stimulated by insulin, epide rmal growth factor, dexamethasone, 17 beta-estradiol and progesterone in vitro. Ovariectomy reduced the growth of RM22-F5 cells in vivo and these cells (but not RM1-4 or RM17-5R) were estrogen-receptor (ER)-pos itive. None of the lines were positive for the progesterone receptor ( PR), Spontaneous lung and lymph-node metastases were observed in nude mice injected with RM22-F5 or RM17-5R cells, respectively. In contrast , RM1-4 cells were non-metastatic but invasive. Karyotype analysis rev ealed that RM22-F5 cells were hyperdiploid, RM17-5R were hypotetraploi d, and RM1-4 were diploid with a sizeable insertion in chromosome I.A point mutation in codon 12 (G to A transition) and loss of the normal allele of the H-ras-1 gene was detected in the DNA from RM22-F5 cells. No p53 mutations were apparent in any of the cell lines. The results indicate that RM22-F5 cells are hormone-dependent with an ER(+)/PR(-) phenotype, while the RM17-5R and RM1-4 lines are hormone-independent a nd ER(-)/PR(-). These cell lines exhibit the spectrum of biological pr operties and genetic alterations observed in human breast cancers and may, therefore, be novel and useful models for understanding sporadic breast cancer in post-menopausal women. (C) 1994 Wiley-Liss, Inc.