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Objective To systematically analyze the relevant literatures of problem-based learning (PBL) and to provide reference for further improvement and innovation. Methods Using bibliometric method and the package "tm" in R, we searched web of science database for PBL relevant literatures from inception to March 19 of 2018. Results A total of 5710 articles published in 77 journals had been collected. The results showed that PBL relevant literatures were increasing from 1976 to 2018. Most papers were published as article, with first authors from 84 countries of the world. The total citation of 5710 articles is 54768 and the average referenced times is 9.59. The research in those articles focused on medical education, health care sciences and engineering. Conclusions PBL has been widely used in various disciplines, especially in medical education. The research involves a wide range but the quality and depth of the study is still need to be improved.
ABSTRACT
Objective To investigate the relationship between DNA topoisomerase Ⅱ α (TOP2A) gene expression and clinicopathological characteristics and its significance of prognostic evaluation for patients with bladder cancer.Methods Bladder cancer gene expression profile GSE13507 (n =165) and GSE31189 (n =52) were obtained.The expression profile and clinical information of patients with bladder cancer were retrospectively analyzed,and the survival analysis was made.Gene set enrichment analysis (GSEA) was conducted to explore the related pathways which were regulated by TOP2A.Results Compared with normal bladder tissues,TOP2A was upregnlated in bladder cancer tissues (5.823 ± 1.079 vs.4.820 ± 1.129),with a statistically significant difference (t =4.336,P ＜ 0.001).The TOP2A gene expression in patients with bladder cancer was correlated with the age of patients (x2 =5.926,P =0.015),sex (x2 =6.046,P =0.014),T staging (x2 =19.484,P ＜ 0.001),N staging (x2 =9.178,P =0.002),M staging (x2 =21.142,P ＜ 0.001),tumor grade (x2 =47.005,P ＜ 0.001),and progression (x2 =11.735,P =0.001),but it was not correlated with recurrence (x2 =0.808,P =0.369).Survival analysis showed that the specific survival rate in the 100 months of TOP2A gene high expression group and low expression group had a statistically significant difference (66.59％ vs.87.95％,x2 =15.820,P ＜ 0.001).The median overall survival time of TOP2A gene high expression group and low expression group were 51.77 months and 134.97 months respectively,with a statistically significant difference (x2 =11.280,P =0.008).The results of GSEA indicated that TOP2A could regulate gene sets related with several pathways like MYC-V1 signaling (P =0.035,FDR =0.132),MYC-V2 signaling (P =0.012,FDR =0.058),E2F signaling (P ＜ 0.001,FDR =0.006) and G2M checkpoint (P =0.006,FDR =0.044).Conclusion The TOP2A gene expression is closely related with clinicopathological characteristics of patients with bladder cancer.TOP2A may function as a potential marker of prognosis for patients with bladder cancer.