CXCL8 interaction with the chemokine receptor CXCR2 induces gelatinase B/MMP-9 release from neutrophils [239], and activation of the chemokine receptor CXCR4 up-regulates gelatinase B/MMP-9 expression in prostate tumour cells, promoting invasion and metastasis [240]. This evidence concerns the gene MMP9 and prostate neoplasm.