Abstract: Objective To investigate the effect of up-regulated cell fate determinant Numb on chemotherapy sensitivity of gastric cancer cells and its mechanism. Methods pcDNA3. 1 plasmidvector and PCDNA3. 1-Numb plasmid were transfected into gastric cancer cell line BGC-823 by liposome transfection technique. The transfected BGC-823 cells were treated with different concentrations of doxorubicin ( ADM ), and the cell proliferation inhibition rate was determined by MTT assay. BGC-823 cells were divided into 4 groups: control group, NC group, Numb group, and Numb + Ferrostatin-1 ( Fer-1) group, and the cell proliferation inhibition rate of each group was determined, and the level of reactive oxygen species (ROS) in each group was detected by DCFH-DA fluorescent probe method. The levels of glutathione (GSH), malondialdehyde (MDA) and theactivity of superoxide dismutase (SOD) were measured by kits, and the concentration of iron ionin cells was determined by the iron ion detection kit. The expression levels of Numb, iron death related pathway factor P53, glutathione peroxidase 4 (GPX4) and solute carrier family 7 member 11(SLC7A11) were detected by qRT-PCR and Western blotting. Results The mRNA and protein relative expression levels of Numb in the Numb group were significantly up-regulated (P < 0. 05), and the cell proliferation inhibition rate was significantly increased after ADM treatment (P< 0. 05)when compared with those in the control and NC groups. In comparison of those in the control group and NC group, the cell proliferation inhibition rate in the Numb group was significantly increased( P< 0. 05), the levels of ROS and MDA in cells were significantly increased (P< 0. 05), the level of GSH content and the activity of SOD was significantly decreased (P < 0. 05), the Fe2 + concentration was significantly increased (P< 0. 05), the expression level of P53 was significantly increased (P< 0. 05), and the expression levels of GPX4 and SLC7A11 were significantly decreased (P < 0. 05). After the intervention by Fer-1 treatment, the proliferation inhibition rate of BGC-823 cells in the Numb + Fer-1 group was significantly decreased (P<0. 05), the levels of ROS and MDA were significantly decreased (P<0. 05), the GSH level and SOD activity were significantly increased (P<0. 05), the Fe2 + concentration was significantly decreased (P < 0. 05), the expression level of P53 were significantly decreased (P<0. 05), and the expression levels of GPX4 and SLC7A11 were significantly up-regulated (P< 0. 05) when compared with those in the Numb group. Conclusion Up-regulation of Numb can enhance the sensitivity of gastric cancer cells to ADM, which may be related to the regulation of P53 / SLC7A11 / GPX4 pathway to induce ferroptosis.

Key words: gastric cancer, chemotherapy sensitivity, Numb, ferroptosis