Fig. 5

Curcumin inhibits chronic As³⁺-induced malignant transformation via enhancing autophagy in normal BEAS-2B cells. A BEAS-2B cells were treated with 6.25, 12.5 μM curcumin and/or 10 μM As³⁺ for 24 h before cell lysates were collected. Anti-p62 immunoprecipitates were analyzed by immunoblot with anti-p62 and anti-LC-3 antibodies for detection of P62-conjugated LC-3, whole protein lysates were collected and p62, LC-3 and β-actin expression were examined by immunoblotting. B BEAS-2B cells were transfected with control siRNA and Nrf2 siRNA. 24 h after transfection cells were then treated with 6.25, 12.5 μM curcumin and/or 10 μM As³⁺ for 24 h before cell lysates were collected. Nrf2, p62, LAMP1, TFEB and LC-3 expression were examined by immunoblotting. C BEAS-2B cells were co-transfected with the mCherry-EGFP-LC3 construct and Nrf2 siRNA. 24 h after transfection cells were then treated with As³⁺ and/or curcumin for 24 h. Yellow arrows indicate autolysosome (red). D BEAS-2B cells were maintained in a medium containing As³⁺ (0 or 0.5 μM) with or without 6.25 μM curcumin for 6 months. Cells were cultured in 0.35% soft agar for 5 weeks. E Colony numbers in the entire dish were counted. The data are expressed as the mean ± SD of three independent experiments (n = 9)