This tissue-specific, alternative promoter usage pattern is conserved in mouse, suggesting a dynamic but epigenetically conserved evolutionary history of CHRNA4. We also found that the expression level of CHRNA4 was highly correlated with nicotine metabolism genes, and CHRNA4 was down-regulated in both hepatocellular carcinoma and tumor-adjacent normal liver tissues. The gene discussed is CHRNA4; the disease is neoplasm.