CXCR4 and neoplasm: A decline in CXCR4 within the tumour parenchyma due to drugs was also observed after staining with immunoperoxidase (Fig. 1d), although quantitative analysis showed statistical significance only with the 50 mg/kg dose of 5-FU (45.7 ± 1.5 compared with 55.9 ± 3.5 for the saline control, P = 0.01).