Fig. 4: CDO1 induces oxidative stress in GC cells.

A, B CDO1^WT markedly increased ROS level while CDO1^Y157F did not alter ROS production in MKN45 (A) and NCI-N87 (B) cells. C, D CDO1^WT rather than CDO1^Y157F decreased GSH/GSSG ratio in MKN45 (C) and NCI-N87 (D) cells. E Heatmap of the fold changes in all antioxidants subjected to HTS relative to MKN45 cells treated with DMSO (Vehicle). Intracellular ATP level, measured using CellTiter-Glo, was used as the surrogate of viable cells. Luminescent reads of engeletin-treated MKN45 cells approximately increased by two times. The fold changes were measured as: Fold change = (Reads _{(antioxidant)}-Reads _(Vehicle)) / Reads _(Vehicle). F Engeletin-treated MKN45 (left panel) or NCI-N87 (right panel) cells with CDO1^WT restoration displayed reduced ROS production compared to these cells exposed to vehicle. G Treatment of Engeletin in MKN45 (left panel) or NCI-N87 (right panel) cells with restored CDO1^WT increased ATP generation relative to vehicle-treated cells. H CCK-8 assays demonstrated that engeletin treatment relieved the inhibition of CDO1^WT on the proliferation in MKN45 (upper panel) or NCI-N87 (bottom panel) cells in vitro. *p < 0.05, **p < 0.01, ***p < 0.001.