CYP2C9 and hepatocellular carcinoma: In order to further obtain the optimal gene combinations of low dimensions, we selected the combinations of one, two or three genes from the 6 important variables (cyp1a2, cyp2c19, cyp2c9, rac1, diablo, and il6) to establish prediction models for HCC, that is, we ran the random forests algorithm 41 times.