Hypoxia Induces Growth Differentiation Factor 15 to Promote the Metastasis of Colorectal Cancer via PERK-eIF2α Signaling

Figure 2

CHOP drives GDF15 expression in CRC cells upon hypoxia exposure. (a, b) HT29 cells exposed to normal air or hypoxia (1% O₂) or hypoxia combined with TUDCA (100 μM) for 12 hours. qRT-PCR analysis of GDF15 mRNA levels (a) and ELISA analysis of GDF15 protein in cell culture (b). (c) Luciferase activity was determined in HT29 cells exposed to normal air or hypoxia or hypoxia combined with TUDCA for 24 hours. (d) qRT-PCR analysis of CHOP and GDF15 in HT29 cells with the transfection of control vector or CHOP-expressing plasmid (CHOP). (e) qRT-PCR analysis of CHOP and GDF15 in HT29 cells with the transfection of shRNA targeted at CHOP or negative control (NC). (f) Luciferase activity was determined in HT29 cells which were transfected with NC or shCHOP, and then exposed to normal air or hypoxia for 24 hours. (g) ChIP assays were conducted byusing IgG as control or anti-Flag antibody in cell lysis from HT29 cells transfected with plasmids of Flag-tagged CHOP or control vector. Representative image of PCR results which were performed to amplify the indicated region of the GDF15 promoter. For c and f, Luc values were presented as fold change after normalized to Renilla activity (RLU). The values of the normal group were set as “1”. All data are shown as mean ± s.e.m. or by unpaired two-tailed Student’s t-test or one-way ANOVA.

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