Figure 1.

As₂O₃ down-regulated CD133 expression in vitro and did not inhibit cell proliferation at lower dosages. (A–C) Treatment of CD133⁺ HCC cells, with 2 μM As₂O₃ reduced CD133 mRNA expression after 24 hours and treatment with 1 μM As₂O₃ did so after 48 hours (A, *P < 0.05) ; treatment with As₂O₃ also reduced CD133 protein expression (B,C; red, CD133; blue, 4′,6-diamidino-2-phenylindole; magnification, ×200). (D) After treatment with 4 μM As₂O₃ for 5 days, the percentage of CD133⁺ Huh7-wt cells decreased from 82.1% to 55.7% (upper panels) and the percentage of CD133⁺ Hep3B-wt cells decreased from 76.1% to 43.8% (lower panels). (E) In a 48-hour assay, 6 μM As₂O₃ inhibited proliferation of HCC CSCs, whereas As₂O₃ at 1–4 μM had little effect on proliferation over the course of 24 or 48 hours (*P < 0.05).