Patients with RCC recurrence or metastasis show poor prognosis. There are already several potential new biomarkers of RCC progression and treatment (16–18). VEGF pathway inhibitor and mTOR inhibitor are the main targeted therapies against RCC. However, the prognosis of advanced RCC patients are still limited if the tumours become resistant to these therapies. Cell mitosis is, to some extent, dependent on the centromere-kinetochore complex, especially cancer cells. Therefore, kinetochore activity may be one of the promising drug targets for cancer treatment. It has been shown that CENPF plays important roles in cell cycle and division. During mitosis, ataxia telangiectasia mutated and Rad3-related (ATR) kinase localizes to centromeres through Aurora A-regulated association with CENPF, allowing ATR to engage replication protein A (RPA)-coated centromeric R loops. After activation, ATR then stimulates Aurora B, preventing lagging chromosomes (19). In our study, we reported the pro-tumour activity of CENPF in RCC cell lines for the first time.
Our results may provide new insights into the RCC proliferation and malignancy. In this study, we revealed that CENPF is highly expressed in RCC tissue and downregulation of CENPF can significantly inhibit RCC cell proliferation and change cell cycle distribution. These results are consistent with the previous studies (13, 14). Interestingly, many studies reported that several genes and non-coding RNAs (ncRNAs) can promote cancer cell proliferation or metastasis via modulating CENPF. For instance, LncRNA MCM3AP-AS1 contributes to breast cancer cell progression through miR-28-5p/CENPF axis (20). Er-Bao Chen et al. report that the HnRNPR-CCNB1/CENPF axis promotes gastric cancer proliferation and metastasis (21). These evidence may further confirm the pro-tumour activity of CENPF. However, how CENPF is overexpressed in RCC cells is still unclear.
Cell cycle progression is one of the determinants of cancer cell malignancy. Cancer cells need to pass from the G1 phase into S phase through a tightly regulated checkpoint. Specifically, the G1/S transition begins in early G1, triggering an increase of D-type cyclins (D1, D2, and D3), which bind to CDK4 or CDK6. This cyclin-CDK complexes translocate to the nucleus where they are phosphorylated. In turn, activated CDK4/6 complexes phosphorylate the retinoblastoma (RB) tumour suppressor protein. RB reduces the expression of S phase genes by directly inhibiting E2F transactivation (22). Therefore, the G1/S transition largely depends on the activity of CDK4/6 and D-type cyclins. In our study, we found out that CENPF inhibition significantly reduced CDK4/6 and Cyclin D1 expression, which may partially explain the phenotype. Our results provide evidence that CENPF downregulation or mutation may sensitizes RCC tumors to cell cycle inhibitors.
In summary, this project found that the expression of CENPF is up-regulated in RCC, and down-regulation of CENPF can inhibit the proliferation of RCC cells. It also clarified the mechanism by which CENPF regulates the cell cycle of RCC by inhibiting the expression of cyclins such as CDK4, CDK6 and CyclinD1. This project has discovered new pathogenic genes and pathogenesis in RCC, which provides a scientific basis for exploring new therapeutic targets.