CXCR4 and cancer: [7], [22], [34]–[36], [38]. While neither NB8-CXCR4 nor N91-CXCR4 clones showed any increased capacity to invade Matrigel® in response to CXCL12, CXCR4 overexpressing PC3 prostate cancer cells indeed showed increased in vitro invasive capacity [30]. This observation made in another cancer type confirms previous reports [22] and suggests that the pro-invasive effects of CXCR4 may be tumour type specific.