Establishment and characterization of new murine breast cancer cell lines

The establishment of two new breast cancer cell lines, MXT+ and MXT-, derived from the murine breast cancer models MXT-M-3,2 MC (hormone-sensitive) and MXT-M-3,2 (ovex) MC (hormone-insensitive), is described. Characterization of the cell lines was performed by investigation of morphology, steroid hormone receptor state, growth kinetics, and drug response as well as by cytogenetic analysis. MXT+ contains estrogen receptors (ER; 6.9 fmol/mg protein) as well as progesterone receptors (PgR; 9.2 fmol/mg protein) and therefore is inhibited by tamoxifen (Tam). MXT- proved to be ER- but PgR+ (23.4 fmol/mg protein) and, as expected, resistant against Tam. The sensitivity of MXT+ and MXT- against a pattern of therapeutically established anti-breast cancer drugs (cDDP, cisplatin; JM-8, carboplatin; DX, adriamycin; 5-FU, 5-fluorouracil; MTX, methotrexate; VLB vinblastine) was studied by use of a computerized, kinetic chemosensitivity assay based on quantification of biomass by staining cells with crystal violet. For each compound the inhibition profile reflecting cytostatic, transient cytotoxic, or cytocidal drug effects as well as development of resistance was evaluated. The following order of activity was found: MTX > VLB > or = DX > cDDP > or = 5-FU > JM-8. The test data of 5-FU, VLB, cDDP, and Tam on MXT+ as well as on MXT- were compared with those from studies on ER+ and ER- human breast cancer cell lines (MCF-7, ZR-75-1, T-47-D, and MDA-MB-231, respectively). They revealed comparable inhibition profiles and sensitivities of human and murine breast cancer cell lines, an indication that the results achieved in combined in vitro-/in vivo tests by use of the murine test models MXT+, MXT-, MXT-M-3,2 MC, and MXT-M-3,2(ovex) MC are relevant for therapy in humans.