RNA Interfering ARID1A Expression Enhances The Antitumor Effect Of ATR Inhibitor AZD6738 Combined With Radiotherapy On Colorectal Cancer

Objective: ARID1 A is the core subunit in the SWI/SNF chromatin remodeling complex and participates in epigenetic regulation,DNA damage response,DNA damage repair,and maintenance of genome stability.In colorectal cancer,ARID1 A mutations and low expression are widespread,which is significantly associated with poor differentiation of colorectal cancer,lymphatic vessel infiltration and metastasis,and distant metastasis.The mutation and low expression are significantly related to the progression and prognosis of colorectal cancer.The combination of small molecule targeted inhibitors and new cancer markers has the potential to significantly improve the efficacy of radiation therapy.At present,the strategy of ATR inhibitor AZD6738,as a radiosensitizer,in combination with radiotherapy is in clinical trials.Under such circumstances,our study will clarify the effect of the absence or low expression of ARID1 A on the antitumor effect of the combination of ATR inhibitor AZD6738 and radiotherapy.Method: Firstly,we used RNA interference technology to simulate ARID1 A deletion and low expression colorectal cancer cells.Then,the proliferation curve,cell viability curve,cell fusion rate and clonal formation were conducted to assess the proliferation ability.And the flow cytometry and immunofluorescence were used to evaluate apoptosis.Finally,the comet experiment and Western blotting were used to quantify DNA damage and repair status.Result: Under the simultaneous treatment of AZD6738 and radiotherapy,the proliferation curve of colorectal cancer cells in the sh RNA-ARID1 A interference group was inhibited,the cell viability and cell fusion rate were reduced,and the cloning formation ability was also weakened.It inhibited proliferation in a radiation dosedependent manner.After the treatment of AZD6738 and radiotherapy,compared with the sh RNA negative control,the expression of apoptosis marker Active-caspase 3 and the ratio of apoptosis were increased in the sh RNA-ARID1 A interference group;the result of the comet experiment and Western blot experiments showed that the colorectal cancer cell in the sh RNA-ARID1 A interference group accumulated the more DNA damage and it had the lower expression of γ-H2 AX,reviewing previous studies found that the increased accumulation of DNA damage might be related to the low expression of γ-H2 AX.Conclusion: In summary,we found that RNA interfering ARID1 A expression enhances the antitumor effect of AZD6738 combined with radiotherapy on colorectal cancer compared with the sh RNA negative control.This may help patients with ARID1 A mutations and low expression colorectal cancer,using ATR inhibitors as radiotherapy sensitizers,to benefit more from radiotherapy.It will also contribute to the beneficiary population selection and a more reasonable patient stratification for the clinical trial of ATR inhibitors and radiotherapy,which can accelerate clinical transformation.