The mRNA expression levels of sex hormone- related genes (ESR2, ESRRB, ESRRG, PGRMC1, PGRMC2, GPER, SHBG) and ER regulatory gene, TFF1 in HCC tissues were significantly lower than those of adjacent tissues, whereas the expression of estrogen-related receptor gene, ESRRA and ER regulatory genes (MTA1 and FOXA1) were higher in tumor tissues (Fig. 8). The gene discussed is GPER1; the disease is hepatocellular carcinoma.