CXCL12 and neoplasm: Recent studies aimed at discriminating those factors indicate high expression in recurrent tumours of p53 tumour suppressor gene [13, 24, 25], the stem cell marker CD166 [38], chemokine receptor CXCR4 and its ligand CXCL12 [35] and also β-catenin accumulation [38, 40, 41].