Research progress of SPP1 in cancer regulation: Tumorigenesis, metastasis, tumor microenvironment, immunity and therapeutic targets (Review).
Secreted phosphoprotein 1 (SPP1, also known as osteopontin, OPN) is a multifunctional matricellular glycoprotein that is aberrantly overexpressed in nearly all major human malignancies. It functions as a central signaling hub that drives tumor initiation, sustains cancer stemness, accelerates invasion and metastasis, r...