CXCR4 and gastric cancer: Additionally, as shown in glioblastoma multiforme [39], tumour samples revealing both, CXCL12 positive tumour cells and CXCR4 positive microvessels were highly significantly associated with high local tumour extent and high UICC stages, further supporting the significance of a functional CXCL12-CXCR4 axis in gastric cancer biology.