GADD45 Determines Chemoresistance and Invasive Growth of Side Population Cells of Human Embryonic Carcinoma
GADD45 determines invasion of SP cells but not SP phenotype. (a) Representative photographs of invasion of NEC8 SP cells after the inhibition of ABCG2 and GADD45 using siRNA. Scale bar = 50 m. (b) Comparison of invasiveness of NEC8 SP cells treated with siRNA. Values are the means of the normalized cell counts to NSC from triplicate invasion assays of three independent experiments. versus NSC. NSC means treatment with nonsilencing control siRNA, G means treatment with GADD45 siRNA, and A means ABCG2 siRNA. versus NSC. (c) Upregulation of GADD45 by treatment with a low concentration of cisplatin. NEC8 cells were incubated with vehicle (cont) or 0.01 M of cisplatin (cis) for 24 hours, and were sorted by FACS. The gene expression of GADD45 in SP (black bar) and non-SP (white bar) cells was evaluated using real-time PCR. The values are the mean ± SD (). versus non-SP (). (d) SP analysis after the upregulation of GADD45. NEC8 cells were incubated with the vehicle (cont) or 0.01 M of cisplatin (cis) for 24 hours, and an SP analysis was performed in the presence (white bar) or absence (black bar) of reserpine. Values are the mean ± SD (). NS means not significant.