Fig. 6

Letrozole inhibits estrogen receptor-positive (ER+) breast cancer cell proliferation indirectly by acting on bone tissues. a Experimental design for comparing relative breast cancer cell numbers during culture with bone tissue supernatants generated in the presence of letrozole vs. control medium containing letrozole. b Bioluminescence imaging (BLI) signal displayed by ER+ MCF-7, and ER- SK-BR-3 and MDA-MB-231 breast cancer cells growing in the presence of conditioned media generated by total hip replacement (THR) specimen THR 116 tissue fragments cultured in DMEM-10%FBS +/− 100 μM letrozole vs. control media (DMEM-10%FBS) +/− 100 μM letrozole. c Averaged triplicate BLI signal detected on plate shown in (b). BLI signal was specifically reduced in MCF-7, but not SK-BR-3 or MDA-MB-231 cells cultured with bone tissue culture supernatants generated in the presence of 100 μM vs. 0 μM letrozole μM (***p = 0.00003), as determined by t test (n = 3, error bars represent standard deviation). No difference was observed for any of the cell lines when 100 μM letrozole was added directly to the control medium