The Role Of RNA Binding Protein QKI-5 In Renal Cell Carcinoma Development

Objective: 1) To analyze the expression pattern and function of QKI-5 in renal cell carcinoma(RCC); 2) To explore the underlying mechanism for the aberrant expression of QKI-5 in RCC development. Methods: 1) the expression of QKI-5 between cc Rcc and matched adjacent normal tissues were tested by using RT-PCR and Western Blot, and the role of QKI-5 in predicting cc RCC patient outcomes were determined by using The Cancer Genome Atlas(TCGA) cc RCC dataset. 2) Overexpressing QKI-5 in kidney cancer cells 786-O and A-498 to observe the function of QKI-5 in the development of RCC and the effect to cell cycle. 3) To reveal the mechanism how QKI-5 regulates cell proliferation and identifying the potential targets of QKI-5 in this process. Results: 1)Downregulation of QKI-5 was commonly observed in primary tumors relative to matched adjacent normal tissues. A downregulation of QKI-5 was also observed in all of the tested cc RCC cell lines compared to HK-2, which derived from human renal proximal epithelial tubular cells. level of QKI-5 in primary tumors was significantly correlated with the T stage, M status, and grade of differentiation; decreased QKI-5 expression significantly correlated with poorer overall survival in cc RCC patients. 2) In vitro assays revealed that the ectopic expression of QKI-5 effectively inhibited cellular proliferation,resulting in significant inhibition of the cellular growth rate and reduction in the colony forming ability of the cells. In vivo experiments also showed tumour growth was significantly suppressed in mice injected with QKI-5-expressing 786-O cells when compared with growth in the controls. Moreover, ectopic expression of QKI-5 in 786-O and A-498 cells significantly increased the proportion of cells in G0/G1 phase and decreased the proportion in S phase and displayed a reduction in cyclin D1 and an accumulation of p21 and p27. 3) The subsequent functional studies showed that QKI-5stabilized RASA1 mRNA via directly binding to the QKI response element region of RASA1, which in turn prevented the activation of the RAS/MAPK/ERK signaling pathway, suppressed cellular proliferation and induced cell cycle arrest. Sequenceanalysis of the 3’-UTR of RASA1 indicated that there was one putative QRE region,RNA-IP assay also confirmed the direct interaction between RASA1 mRNA and QKI-5.Conclusions: We find that the expression of QKI-5 is down regaluted in kidney tumor tissues, and the expression of QKI-5 is negatively correlate with the tumor T stage and grade, and is positively correlate with the survival time of patients; our data establish a suppressive role for QKI in cc RCC tumourigenesis and present a new QKI/RASA1/MAPK/ERK pathway in regulation of cell proliferation.