As excellent demonstration courses with distinctive teaching characteristics and the first-class teaching level, quality courses can improve the quality and effects of standardized training. Based on years of experience in teaching and training and focusing on the problems in standardized training, we have established a series of quality courses, including targeted short video lessons for systematic and comprehensive learning and module-based training, flipped classroom teaching based on case analysis, and real-time remote teaching and online teaching under the background of "Internet Plus". These courses aim at strengthening students' theoretical basis and practical ability and building their clinical thinking, so as to improve teaching effects and training quality.

[Abstract] Objective: To investigate the effect of metformin on the senescence-associated secretory phenotype (SASP) of doxorubicin-induced gastric cancer BGC823 cells. Methods: Human gastric cancer BGC823 cells were cultured in vitro and treated with doxorubicin at gradient concentrations (50, 100, 150 and 200 nmol/L). Cell senescence was detected by SA-β-gal staining, and SASP factor expression was detected by ELISA. The effects of metformin on cell senescence and SASP factor secretion induced by doxorubicin (100 nmol/L) were observed by adding gradient concentrations of metformin (0, 5, 10 and 20 mmol/L). Results: With the increase of doxorubicin concentration and treatment time, the senescence rate of gastric cancer BGC823 cells increased first and then decreased. At 96 h after 100 nmol/L doxorubicin treatment, the peak aging rate reached 68.7%, accompanied with significantly increased expressions of SASP factors IL-1a, IL-6, IL-8 and CXCL1. The proportion of senescent cells was (55.2±1.9)%, (48.7±2.2)% and (40.8±2.3)% respectively under the effects of 5, 10 and 20 mmol/L metformin, which was significantly lower than that in the non-metformin treatment group (P< 0.01). At the same time, with the increase of metformin concentration, the production of SASP factors IL-1α, IL-6, IL-8 and CXCL1 showed a gradient decline. Compared with the non-metformin treatment group, IL-6 and IL-8 decreased significantly under the effect of metformin above 10 mmol/L (P<0.05 or P<0.01), while IL-1α and CXCL1 decreased significantly under the effect of 20 mmol/L metformin (all P<0.05). Conclusion: Metformin can inhibit the senescence and SASP production of gastric cancer cells induced by doxorubicin.