GADD45𝛽 Determines Chemoresistance and Invasive Growth of Side Population Cells of Human Embryonic Carcinoma

Figure 7

GADD45$\beta$ 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$\beta$ using siRNA. Scale bar = 50 $\mu$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. ${}^{*}P<.005$ versus NSC. NSC means treatment with nonsilencing control siRNA, G means treatment with GADD45$\beta$ siRNA, and A means ABCG2 siRNA. ${}^{*}P<.001$ versus NSC. (c) Upregulation of GADD45$\beta$ by treatment with a low concentration of cisplatin. NEC8 cells were incubated with vehicle (cont) or 0.01 $\mu$M of cisplatin (cis) for 24 hours, and were sorted by FACS. The gene expression of GADD45$\beta$ in SP (black bar) and non-SP (white bar) cells was evaluated using real-time PCR. The values are the mean ± SD ($n=8$). ${}^{*}P<.001$ versus non-SP ($n=8$). (d) SP analysis after the upregulation of GADD45$\beta$. NEC8 cells were incubated with the vehicle (cont) or 0.01 $\mu$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 ($n=8$). NS means not significant.

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