F-box protein FBXO21 overexpression inhibits the proliferation and metastasis of clear cell renal cell carcinoma and is closely related to the CREB pathway and tumor immune cell infiltration.

BACKGROUND: Many studies have shown that F-box proteins regulate epithelial-mesenchymal transition, which is closely related to tumor metastasis. However, there is still limited research on the role of F-box proteins in renal cell carcinoma (RCC). METHODS: Public databases were used to screen differentially expressed genes among 37 F-box proteins in clear cell RCC (ccRCC). The expression of the differential gene FBXO21 and its prognostic value were verified by RT-qPCR and immunohistochemistry. Pyrosequencing was used to detect the regulatory effect of DNA methylation on FBXO21 expression. The effects of FBXO21 expression on cell proliferation and metastasis were clarified through cell phenotype experiments and animal models. The relationship between FBXO21 expression and the infiltration levels of tumor immune cells was also analyzed. GSEA and Western blot were used to identify the downstream molecular pathways associated with FBXO21 expression. RESULTS: Our results revealed that FBXO21 was significantly underexpressed in ccRCC and that increased FBXO21 expression predicted a better patient prognosis. The promoter region of FBXO21 exhibited DNA hypermethylation, and FBXO21 expression was significantly restored after demethylation. In addition, FBXO21 overexpression significantly inhibited the proliferation and metastasis of ccRCC cells both in vitro and in vivo. Mechanistically, FBXO21 expression was related to the stroma score and the infiltration levels of immune infiltrating cells associated with prognosis. Moreover, FBXO21 overexpression increased the expression of key molecules in the CREB pathway. CONCLUSIONS: These results suggest that FBXO21 is a novel prognostic biomarker for ccRCC patients and functions as a tumor suppressor gene. Moreover, FBXO21 may regulate the CREB pathway and is closely related to tumor immune cell infiltration in ccRCC.