ABCG2 and cancer: Compared with control xenograft tumors, the mRNA levels of cancer stemness-related genes, including ABCG2, BMI1, NANOG, KLF4, and OCT4 were increased and the protein expression of ABCG2, Oct4, Bmi-1, and CD44 were also increased in HBx-expressing xenograft tumors (Figure 1D,E).