CXCL12 and cancer: Combined with previous results57 and our present meta-analysis results, we put forward a simple hypothesis that the SDF-1 rs1801157 polymorphism, which has a G > A transition in the 3′-UTR, may have an important regulatory function of up-regulating SDF-1 production and the high serum concentrations of SDF-1 might contribute to cancer susceptibility.