In a study of ERα-66 and ERα-36 mRNA expression in non-tumor, cirrhotic and malignant liver tissues and HCC cell lines, it was found that ERα-66 was highly expressed in non-tumor tissues, cirrhotic tissues showed a lower level, whereas its expression decreased or became undetectable in HCC tissues and cell lines. The gene discussed is ESR1; the disease is hepatocellular carcinoma.