CYP1A2 and hepatocellular carcinoma: Among 84 drug resistance related genes, using 2-fold as cutoff point, 4 down-regulated genes (DHFR, SULT1E1, RARB and CYP3A4) and 2 up-regulated genes (CYP1A1 and CYP1A2) were identified in HCC cells after YQ23 treatment (Table 1, Figure 5A).