Consistently, depletion of CDX2 in lung cancer promoted cell invasion and metastasis by increasing Snail expression.51 Intriguingly, Gross et al. reported that Snail could repress CDX2 transcription in colon cancer cells.52 Our previous study also indicated that Snail is involved in the HIF-α-induced downregulation of CDX2,53 implying that a positive feedback mechanism might exist between CDX2 and Snail; however, the exact mechanism remains to be further elucidated. The gene discussed is SNAI1; the disease is lung carcinoma.