CXCL12 and neoplasm: Moreover, C-X-C-type chemokines including CXCL8 (IL-8), CXCL2, and CXCL12 secreted by CAFs are also involved in tumor proliferation by promoting angiogenesis and metastasis (CXCL8 & CXCL12) and increasing PD-L1 expression (CXCL2) [9,12,13,14].