Hypoxia-inducible factor-1 modulates upregulation of mutT homolog-1 in colorectal cancer

Figure 3 Hypoxia-inducible factor-1α is involved in hypoxia-enhanced expression of mutT homolog-1. SW480 and HT-29 cells transfected with either siRNA targeting HIF-1α or mock siRNA were exposed to hypoxia for 72 h or normoxia. qRT-PCR showed that siRNA targeting HIF-1α significantly inhibited expression of HIF-1α mRNA in colon cancer cells as compared to cells treated with mock siRNA(P = 0.0003, P = 0.0007) (A and C). Western blotting showed that siRNA targeting HIF-1α significantly suppressed expression of HIF-1α protein under hypoxia, but the mock siRNA group was unaffected (B and D). MTH-1 mRNA expression and MTH-1 protein were decreased by silencing of HIF-1α at 72 h (P = 0.002, P = 0.003) (E and F). The residual 8-oxo-dGTP base lesions were markedly higher in the HIF-1α siRNA groups compared to the mock siRNA groups of SW480 and HT-29 cells (G) (48 h: P = 0.011, P = 0.016; 72 h: P = 0.003, P = 0.000). ^aP < 0.05, ^bP < 0.01 vs control. NS: Non-significant; siRNA: Small interfering RNA; HIF-1α: Hypoxia-inducible factor-1α; MTH-1: MutT homolog-1; qRT-PCR: Quantitative real-time polymerase chain reaction.