We compared the changes of NTCP expression in two cell lines (HLCZ01 and HepG2-NTCP) under HBV infection and found that HLCZ01 cells infected with HBV for a short or long time had comparable levels of intracellular NTCP protein compared with the original HLCZ01 cells, whereas NTCP expression in HepG2-NTCP cells gradually declined with the duration of infection (Fig. 4F). The gene discussed is SLC10A1; the disease is infection.