SPP1 and cancer: Abbreviations: CAF, Cancer associated fibroblast; DC, Dendritic cell; FSP, Fibroblast specific protein; IGF, Insulin-like growth factor; MDSC, Myeloid-derived suppressive cell; MMP, Matrix metalloproteinaseo; NO, Nitric Oxide; OPN, Osteopontin; ROS, Reactive oxygen species; TGF, Transforming growth factor; TNF, Tumor Necrosis Factor; Treg, Regulatory T cell; TWIST, Twist family bHLH transcription factor; VEGF, Vascular endothelial growth factor; SMA, Smooth muscle actin.