The Influence Of Compound GA13315 On Chemotherapy Sensitivity Of Tumor Cells And The Related Mechanism Exploring

[Objective]Compound GA13315 is a gibberellin derivative,a novel tetracyclic diterpenoids.Previous studies have shown that GA13315 can significantly increase the sensitivityof tumor cells with multidrug resistance(MDR)to a variety of previously chemotherapeutic drugs,and dose-dependently increase the chemosensitivity of MDRcells that high-expression of drug transporters.For human breast cancer MCF-7/Adrmultidrug resistant cells,the activity of GA13315 alone was stronger than that ofMCF-7 sensitive cells.GA13315 also significantly increased the effect ofTopo ?(topoisomerase ?)inhibitor irinotecan(Irinotecan,CPT-11)and Topo ?(topoisomerase ?)inhibitor etoposide(Etoposide,VP16)on HCT116(Human colon cancer cell line),especially for CPT-11.In order to explore the mechanism of chemosensitization of compound GA13315,this study was carried out in the aspects of DNA damage repair,Topo expression level and apoptosis regulation on the previous basis,to find out the mechanism or mode of chemosensitization of GA13315,evaluate the potential of GA13315 as an adjuvant chemotherapeutic drug.[Methods]Human colon cancer cell HCT116,human breast cancer cell MCF-7 and multidrug resistant human breast cancer cell MCF-7/adr were used as models to continuously induce the above three cells for 12 weeks by low dose of GA13315.To explore the changes in cellular chemosensitivity and related mechanisms by follow methods and technology.1.CCK-8 assay was used to detect the sensitivity of cells to chemotherapeutic drugs at different time points of GA13315 induction;2.qRT-PCR and Western blot to detect GA13315 induced at different time points,intracellular Topo,DNA damage repair related genes,expression of apoptosis-related genes;3.Single cell gel electrophoresis(SCGE)was used to detect whether GA13315 could damage DNA;4.Using the kit to identify the mode of action of the drug targeting specially DNA Topo.[Results]1.After treated with low concentration GA13315,the sensitivity of HCT116,MCF-7 and MCF-7/adr to different chemotherapeutic drugs was different,and the sensitivityto Topo inhibitors was significantly different.It is suggested that the change of chemosensitivity of GA13315 to tumor cells is related to the effect of Topo on tumor cells;2.After treated with low concentration of GA13315 for a long time,the sensitivity of HCT116,MCF-7 and MCF-7/adr cells to different chemotherapeutic drugs,especially Topo inhibitory chemotherapeutic drugs,changed significantly.It also had significant or different effects on the expression of topo,DNA damage repair gene Chkl and Tdp1,the expression of apoptosis-regulating genes Bax and Bcl-2 also have significant or different degrees of influence,but the correlation with cell sensitivity was difficult to analyze;3.Compound GA13315 had no significant effect on the ratio of apoptosis regulator gene Bax to Bcl-2,and its chemosensitization effect did not seem to be significantly related to apoptosis pathway;4.The identification of Topo action mode of compounds and drug targeting cells suggested that CPT-? and VP-16 mainly stabilized Topo-DNA complex and were Topo agents,while GA13315 mainly inhibited the enzyme activity of Topo.It is suggested that the influence mechanism of the two on the function of DNA Topo isdifferent;5.After treatment with GA13315,DDP,CPT-11 and VP16,comet-like trailingphenomenon was observed in HCT116,MCF-7 and MCF-7/adr cells,indicating that DNA was significantly damaged and DNA fragmentation was caused.Although the mechanisms of DNA damage are different,the final result is DNA fragmentation,which leads to cell death.[Conclusion]The effects of compound GA13315 on the sensitivity of different cells andchemotherapeutic drugs were different,and the effects on the sensitivity of Topo inhibitors were obvious,it is suggested that the change of chemosensitivity of GA13315 to tumor cells is related to the effect on cell Topo;GA13315 is the enzyme activity inhibitor of cell Topo,while CPT-11 and VP16 are Topo agents;GA13315 can lead to DNA fragmentation and then induce cell death.Topo inhibitors CPT-?,VP-1 and GA13315 interfere with Topo function of tumor cells in different ways and in different ways,resulting in DNA fragmentation and cell death.However,under what conditions the two play a synergistic role and under whatconditions there is antagonism,there is a complex interaction,this study can not be answered.