Comprehensive bioinformatics analysis of the E2F family in human clear cell renal cell carcinoma

Clear cell renal cell carcinoma (ccRCC) originates from renal tubular epithelial cells and is the most common pathological renal cell carcinoma type with the worst prognosis. The relationship between the expression, prognosis and mechanism of ccRCC and the E2F family remains challenging. In the present study, RNA sequencing and clinical data of ccRCC from The Cancer Genome Atlas and two datasets, GSE36895 and GSE53757, from the Gene Expression Omnibus were used to identify the role of the E2F family in ccRCC. A total of 10 groups of tumor tissues and paired-normal tissues from patients with ccRCC were verified by reverse transcription-quantitative PCR. the expression, tumor grade and stage, prognosis and regulatory mechanism of the E2F family in ccRCC were analyzed. It was found that the expression levels of E2F1 to 4 and 6 to 8 were higher in ccRCC tissues than in normal tissues, whereas the expression level of E2F5 was lower in the former than in the latter. The expression levels of E2F1 to 8 were correlated with tumor stage and grade. Low expression of E2F1 to 5 and 7 to 8 was significantly associated with longer overall survival, disease-specific survival and progression-free survival times. The data revealed that the E2F family rarely has genetic mutations. The expression of E2F1, E2F2, E2F5, E2F7 and E2F8 was significantly correlated with DNA methylation, and E2F1 to E2F7 were significantly correlated with copy number and the data showed that the expression of E2Fs was significantly correlated with the cell cycle. The results of the present study suggested that E2F family genes may be potential targets for ccRCC molecular diagnosis and targeted therapy.