SPP1 and breast cancer: Gene expression analysis revealed increased expression of SPP1, BGLAP, VEGF, ALPL, RUNX2 and TNFRSF11B candidate genes in G4 (MC3T3-E1 + BC-HA-anti-BMP-2 cells + 200 ng/mL BMP-2 protein), some being earlier and others later than the analyzed period.