ACP5 and breast cancer: Overall, the number of TRAP-positive, multinucleated (>3 nuclei) osteoclasts produced from a tri-culture of pre-osteoclasts plus MDA-MB-231 breast cancer cells plus EO-231 cells or a tri-culture of pre-osteoclasts plus MCF-7 breast cancer cells plus EO-MCF-7 breast cancer cells were reduced compared to the number of osteoclasts formed from tri-cultures of pre-osteoclasts plus MDA-MB-231 breast cancer cells plus naïve osteoblasts or tri-culture of pre-osteoclasts plus MCF-7 breast cancer cells plus naïve osteoblasts (Figure 4e,i).