Functional classification of DEGs by the DAVID gene functional classification tool (https://david.ncifcrf.gov/). The tool utilizes the comprehensive DAVID Knowledgebase which pulls together multiple sources of functional annotations. Representative classifications were selected base on P values (P ≤ 0.05) by kappa statistics. Classification analysis of the upregulated and downregulated DEGs was performed based on the following: biological process, molecular function and cellular component.