CXCL12 and neoplasm: It has been previously demonstrated in a ALTS1C1 tumor model [18] that the invading tumor front has a distinct microenvironment from that of the primary tumor core, such as a different ratio of the TAM subtypes and a higher MVD associated with higher levels of vascular endothelial growth factor receptor-1 (VEGFR-1) and SDF-1 expression.