R software v 3.6.1

Statistical analysis was done using R software (V.3.6.1) and SPSS software (ver. 25.0). Wilcoxon rank sum test and chi-square test were conducted for continuous and categorical variables, respectively. For all analysis, two-by-two pairs indicate statistically significant differences. *, **, *** and **** indicate, respectively <0.05, <0.01, <0.001, and <0.0001.

Statistical analyses were conducted using R software (v.3.6.1) and SPSS 22. Median value of CDKL2 expression was chosen as the cut-off value. Clinicopathological features associated with high and low CDKL2 expression groups were analyzed using the chi-square and Fisher exact tests. Additionally, correlation between CDKL2 expression and clinicopathological features was analyzed using Wilcoxon signed-rank test. Kruskal–Wallis test was used for multigroup comparison (such as tumor stage, clinical stage, and pathological grade). To estimate the influence of CDKL2 expression on survival and clinicopathological factors, overall survival (OS) in TCGA patients was assessed using Cox regression and the Kaplan–Meier method. p < 0.05 was considered significant.