ACP5 and breast cancer: When normalized to bone perimeter, we found a 62% reduction in the surface size of TRAP-positive osteoclasts produced in the presence of MDA-MB-231 breast cancer cells plus EO-231 cells when compared to the surface size of TRAP-positive osteoclasts produced in the presence of MDA-MB-231 breast cancer cells plus naïve osteoblasts (Figure 5e).