Objective To investigate the effect of ubiquitin specific peptidase 22 (USP22) on the occurrence and development of esophageal squamous cell carcinoma (ESCC) under hypoxic conditions, and its regulatory relationship with hypoxia-inducible factor-1α (HIF-1α). Methods Western blotting and quantitative polymerase chain reaction were used to detect the differences in USP22 protein and mRNA expression between normal esophageal epithelial cells HEEC and ESCC cell lines KYSE30, KYSE150, EC9706, and TE-1 under normoxic (5% CO2, 20% O2, 75% N2) and hypoxic (5% CO2, 1% O2, 94% N2) conditions. By transfecting USP22 plasmid or siUSP22, ESCC cells were divided into a normoxia control group, a normoxia+USP22 group, a normoxia+siUSP22 group, a hypoxia control group, a hypoxia+USP22 group, and a hypoxia+siUSP22 group. The proliferation and migration abilities of cells in each group were detected. The expression of USP22 and HIF-1α under hypoxic conditions after up-regulating or down-regulating USP22 was detected, and their regulatory relationship was verified. The interaction between USP22 and HIF-1α was verified by co-immunoprecipitation (Co-IP) technique. Results Compared with HEEC cells, the expression of USP22 in ESCC cells was significantly increased (P<0.05). Up-regulation of USP22 expression promoted the proliferation and migration of ESCC cells, while silencing USP22 inhibited the proliferation and migration of ESCC cells (P<0.05). Under hypoxic conditions, the expression of USP22 and HIF-1α increased, and with the up-regulation of USP22 expression, the expression of HIF-1α also significantly increased (P<0.05). Co-IP experiment confirmed the binding between USP22 and HIF-1α. Conclusion Up-regulation of USP22 expression promotes the proliferation and migration of ESCC cells. Hypoxia microenvironment can induce the increase of USP22 expression in ESCC. USP22 may participate in the regulation of the occurrence and development of ESCC by directly binding to HIF-1α.

Taking case discussion of clinical treatment options of primary liver cancer during clinical internship as an example, the course design of basic elements of case-based learning (CBL) was discussed. The purpose of clinical practice is to cultivate the clinical thinking ability of "selecting the best one from multiple treatment options", which is suitable for taking CBL teaching method. The design of CBL course includes 8 elements: teaching object, purpose, objectives, course content, implementation plan, key points for assessment, course evaluation and reference materials. The core points of the design of CBL course are that: ①The teaching objectives include knowledge, ability and professionalism; ②The course content should includes the training of decision-making organizations and clinical thinking ability of selecting the best one from multiple treatment options; ③The general CBL teaching procedure can be adopted in the implementation of the scheme that focuses on the decision-making issues defined in each decision-making step. The teaching practice of CBL on primary liver cancer cases discussion shows the basic design of CBL course is universal, which is helpful for teachers to design and implement CBL course on clinical treatment options.