CXCR4 and gastric cancer: Overall, we found that 8 CpGs in GPC3, 15 CpGs in LOX, 14 CpGs in CAV1, 13 CpGs in SERPINE1, 12 CpGs in CXCR4 and 23 CpGs in SDC2 were significantly associated with prognosis of GC (Additional file 2: Table S1).