ESTABLISHMENT AND CHARACTERIZATION OF 3 NEW BREAST-CANCER CELL-LINES

We have established and characterized 3 new breast-cancer cell lines f rom pleural effusions of patients with advanced breast cancer. All 3 c ell lines, designated IBEP-1, IBEP-2 and IBEP-3, showed typical ultras tructural characteristics of epithelial mammary tumor cells. Electron microscopy showed, among other characteristics, the presence of numero us microvilli, desmosomal junctions, intracytoplasmic duct-like vacuol es, well-developed endoplasmic reticulum and large nuclei. Immunohisto chemical and biochemical studies revealed that the 3 cell lines expres sed cytokeratin, epithelial membrane antigen, CEA and CA 15-3, but all showed negative immunoreaction for vimentin. On the other hand, other antigens (LEU-M1, GCDFP 15, c-erbB-2) were expressed by some of the c ell lines, but in a variable manner. Ploidy studies confirmed the neop lastic origin of the cell lines. The doubling times were 68 hr for IBE P-1, 29 hr for IBEP-2 and 39 hr for IBEP-3. Only IBEP-2 cells expresse d estrogen receptors (ER+), which were down-regulated after preincubat ion with E-2, but they did not express progesterone receptors (PgR(-)) . IBEP-1 and IBEP-3 cells were ER- but expressed PgR (PgR(+)). In thes e 2 cell lines, PgR were downregulated after pre-incubation of the cel ls with progesterone (10(-8) M) for 24 hr. Estradiol (E-2) increased t he proliferation rate of IBEP-2 cells and progesterone increased the p roliferation of IBEP-1 and -3 cell lines. S.C. injection of the 3 IBEP cell lines into nude mice resulted in the growth of solid tumors betw een 11 and 16 weeks after inoculation. These cell lines could thus be new models for studying various aspects of the biology and the tumorig enicity of breast-cancer cells. A major interest of these new cell lin es is that 2 of them were ER- and PgR(+), which is an exceptional phen otypic feature. These 2 cell lines could be interesting models for stu dying the regulation of PgR and the effects of progestins and antiprog estins independently of the presence of ER. (C) 1998 Wiley-Liss, Inc.