CXCL12 and prostate cancer: Within the tumour microenvironment, prostate cancer cells and infiltrating immune cells release an array of pro-inflammatory cytokines including interleukin-1β (IL-1β), IL-6, and tumour necrosis factor alpha (TNFα), as well as chemokines (C–C motif ligands) such as CXCL1, CXCL8 (IL-8), CXCL12 and CCL2, that have a pivotal role in the initiation, progression and metastasis of prostate cancer [58, 71, 100].