The Role And Mechanism Of Alternative Splicing Factor SF3b1 In Radiation Sensitivity Of Human Cervical Cancer HeLa Cells

Cervical cancer is the most common malignant tumour of female reproductive system,and its morbidity and mortality rank second among malignant tumors of female reproductive system.Radiotherapy is one of the main methods for the treatment of cervical cancer.Radiation resistance of cervical cancer cells to radiation is an important issue in the treatment of cervical cancer.Improving the sensitivity of cervical cancer cells to radiation is the focus of many researchers.Recently,there is increasing evidence that changes in Pre-RNA alternative splicing patterns play a crucial role in cancer and other diseases.In recent years,with the approval and application of a new class of drugs for splicers,the application of alternative splicing in cancer has attracted widespread attention,and splicesome has become an attractive target for cancer therapy.SF3b1,a subunit of splicesome,is mainly involved in intracellular gene transcription,mRNA stabilization,alternative splicing,and other functions.Through literature review,we selected pladienolide B,a small molecule targeting SF3b1,as an inhibitor of down-regulation of SF3b1,to investigate the regulation of different splicing of transcription factor p73 gene,the expression of key proteins related to apoptotic pathway,the induction of apoptosis and cycle arrest after down-regulation of SF3b1,and explored the effect on the radiation sensitivity of HeLa cells after down-regulation of SF3b1 by pladienolide B.Our results showed that:（1）SF3b1 inhibited HeLa cell proliferation in a dose-and time-dependent manner within the concentration range of 0-2 nM pladienolide B,and induced G2/M cycle arrest and cell apoptosis.Down-regulation of SF3b1 by pladienolide B could induce the increase of apoptotic p73 splicer Tap73,thereby up-regulating Bax/Bcl-2 ratio,cytochrome c release and caspase-3 expression.The results showed that SF3b1 played a key role in cell cycle arrest,apoptosis induction and p73 splicing of human cervical cancer cells,suggesting that SF3b1could be used as a potential target for the treatment of cervical cancer.（2）When SF3b1 was down-regulated by pladienolide B combined with X-ray and ¹²C⁶⁺ion beam irradiation,the cell proliferation and clone formation rate of HeLa cells in 2 Gy X-ray and¹²C⁶⁺ion beam irradiation superimposed with 0.025 nM pladienolide B were significantly lower than those in the simple irradiation group,and cell apoptosis and cycle arrest were induced.2 Gy¹²C⁶⁺ion beam had more obvious apoptotic induction effect.It is indicated that pladienolide B can enhance the radiosensitivity of HeLa cells by down-regulating SF3b1,synergistic X-ray and ¹²C⁶⁺ion beam,suggesting that pladienolide B may be used as a drug for synergistic radiotherapy in clinic.