Forkhead box J1 expression is upregulated and correlated with prognosis in patients with clear cell renal cell carcinoma

The forkhead box (FOX) family of transcription factors are considered to have a role in tumorigenesis. FOXJ1 is a member of the FOX family; however, its function in human renal cell carcinoma (RCC) has remained to be elucidated. Therefore, the present study evaluated the expression of FOXJ1 in human clear cell RCC and the effect of FOXJ1 on the proliferative ability of RCC cells. The RCC specimens analyzed in the present study were obtained from 286 patients with RCC who underwent nephrectomy. FOXJ1 mRNA expression levels were determined using reverse transcription-quantitative polymerase chain reaction, and FOXJ1 protein expression levels were determined using immunohistochemistry and western blot analysis. To determine the effect of FOXJ1 on the proliferative ability of RCC cells, the expression of FOXJ1 was decreased using small interfering (si) RNA, and a FOXJ1 vector was stably transfected into RCC cell lines. The proliferative ability of RCC cells was then examined using a WST-1 assay and xenograft experiments with BALB/c nude mice, where the association between FOXJ1 expression and patient survival was determined using Kaplan-Meier analysis. FOXJ1 expression was significantly higher in RCC tissues compared with that of healthy renal tissues. Furthermore, FOXJ1 expression was associated with tumor stage, histologic grade and size. In addition, FOXJ1 significantly enhanced the proliferation of RCC cells in vitro and in vivo. The present study identified that FOXJ1 expression was upregulated in RCC and enhanced the proliferative ability of RCC cells. Therefore, FOXJ1 may serve as an independent prognostic marker and a therapeutic target for the treatment of patients with RCC.