The derangement of the cell cycle facilitates uncontrolled cell proliferation and acquisition of genetic alterations favorable for malignancy. However, the protein expression profiles of E2 F family cell cycle regulators in clear cell renal cell carcinoma (ccRCC) have not yet been thoroughly investigated. In this study, we aimed to examine the protein expression profiles and prognostic value of E2 F1, E2 F3, and E2 F4 in ccRCC cases. The immunohistochemical expression of E2 F1, E2 F3, and E2 F4 was quantitatively scored in 180 ccRCC tumor tissues and 79 normal kidney tissues. The prognostic implications of these E2 F members were determined. We found that ccRCC tumor cells showed higher nuclear expression of E2 F1, E2 F3 and E2 F4 than normal kidney samples. High E2 F1 and E2 F3 expression in tumor cells was associated with poor prognostic factors of ccRCC, whereas high E2 F4 correlated with beneficial prognostic factors. High expression of E2 F1 and E2 F3 in tumor cells was correlated with a poor overall and recurrence-free survival, while high E2 F4 expression did not. In conclusion, E2 F1, E2 F3 and E2 F4 may function as oncogenes during tumorigenesis of ccRCC, although they contribute to the progression of ccRCC in different ways. Additional studies are required to clarify the conflicting role of E2 F4 in the tumor evolution of ccRCC.
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