SPP1 and neoplasm: Through interaction with its receptors, osteopontin and its most-described splicing variants can activate signaling cascades, such as PI3K/AKT and MAPK/ERK, leading to the modulation of EMT-related transcription factor and gene expression, which has been described in several tumor types such as melanoma, breast, ovarian, liver, hepatocellular, colorectal and gastric cancers [5,61].