The Inhibition Of Notch1 Activation In Oxaliplatin-induced DNA Damage In Colorectal Cancer Cells

Colorectal cancer is one of the most common gastrointestinal tumors.The incidence of colorectal cancer in China accounts for 24.3% of the world.Currently,surgery is the treatment of choice.For patients who cannot receive hand treatment,chemotherapy is mainly used.However,as the course of disease progresses,the resistance caused by chemotherapy greatly reduces the therapeutic effect.Therefore,we need to further explore the mechanism of chemotherapy resistance in colorectal cancer and provide new strategies for clinical treatment of colorectal cancer.Notch signaling pathway,which is highly conserved in evolution,is involved in the apoptosis,proliferation and differentiation of various tissues and organs.Notch is closely related to various signal transduction pathways such as Ras,m TOR and NF-?B.Overexpression of Notch receptor or ligand was found in solid tumors such as breast cancer,gastric cancer,and lung cancer.Notch1 is one of the main receptors of the Notch signaling pathway,and regulates downstream targets by specifically binding to the ligand.In the occurrence and development of many malignant tumors,abnormal expression of Notch1 exists.And it has been proved to be related to tumor radiotherapy and chemotherapy resistance.Oxaliplatin is a first-line drug for colorectal cancer.The main molecular mechanism for its therapeutic effect is to cause DNA damage.In the process of DNA damage response,the key molecular protein ATM protein can initiate damage repair procedures.When the damage is beyond the tolerance range and cannot be repaired,the apoptotic program is started.Activated Notch1 can promote cell apoptosis in response to radiation-induced DNA damage by acting on ATM proteins.Based on the above research background,we hope to further explore the role of activated Notch1 in the process of oxaliplatin-induced colorectal cancer cell DNA damage.We selected two colorectal cells,DLD1 and SW620,and used two modes of administration: that is,oxaliplatin alone,oxaliplatin combined with DAPT.Apoptosis of DLD1 and SW620 cells,and DNA damage in both cells were then detected.To investigate the regulatory mechanism of Notch1 activation on oxaliplatin-induced DNA damage and apoptosis in colorectal cancer cells.Method:1.CCK-8 was used to detect the effects of oxaliplatin on the viability and proliferation of DLD1 and SW620 cells.2.Western Blot and flow cytometry were used to detect the effects of oxaliplatin on DNA damage in DLD1 and SW620 cells.Effects of DAPT combined with oxaliplatin on DNA damage and apoptosis in DLD1 and SW620 cells3.Western Blot was used to detect the effects of oxaliplatin on DNA damage in DLD1 and SW620 cells under different time effects.Effect of DAPT on the expression of NICD protein in DLD1 and SW620 cells.4.CCK-8 was used to detect the effect of DAPT on the viability of DLD1 and SW620 cells.Effects of DAPT combined with oxaliplatin on the viability and proliferation of DLD1 and SW620 cells.Results:1.With the doubling of oxaliplatin concentration,the cell viability and proliferation ability of DLD1 and SW620 cells were significantly inhibited.The expression of NICD protein increased,and the number of apoptosis increased.The expression of ?-H2 AX,p-CHK2 and p-ATM protein gradually increased.At relatively low concentrations,the expression of p-BRCA1 protein increased,and as the concentration of oxaliplatin doubled,the expression decreased.The expression of p-P53 and cleaved-caspase3 protein gradually increased.2.DAPT can inhibit the expression of NICD protein in DLD1 and SW620 cells,and has a certain inhibitory effect on the viability of the two cells.3.Compared with the control group,DAPT alone,and oxaliplatin group,the combined group had more obvious inhibition on the viability and proliferation abilityof DLD1 and SW62 O cells.?-H2 AX,p-CHK2,p-ATM,p-P53,and cleaved-caspase3 protein expression gradually increased.4.Oxaliplatin continuously acts with time(0.5h,1h,2h,8h,16 h,24h),the expression of ?-H2 AX and p-P53 protein in two types of cells gradually increased,and the expression of p-ATM protein increased first with time Post-decrease.Conclusion:1.In colorectal cancer,oxaliplatin induced DNA damage response and p53-mediated apoptosis,while Notch1 activity increased.2.In the presence of oxaliplatin,inhibition of Notch1 activation can enhance p53-mediated apoptosis associated with DNA damage response in colorectal cancer cells.