Clinical And Translational Study Of Delayed EGFR-TKI Acquired Resistance By Radiotherapy In Non-small-cell Lung Cancer

Objective:Epidermal growth factor receptor tyrosine kinase inhibitor(EGFR-TKI)has shown significant efficacy in the treatment of advanced non-small-cell lung cancer(NSCLC).However,the median progression-free survival(PFS)of patients is only 8-18 months.The emergence of acquired resistance to EGFR-TKI is the biggest bottleneck in the clinical application of EGFR-TKI.Therefore,it is very important to find drugs or treatments with less toxic and well tolerated side effects to delay or even change the process of acquired resistance.Radiotherapy is an important means to control the progression of lung cancer,but there is still no consensus on the optimal timing of EGFR-TKI combined radiotherapy in clinical practice.The purpose of this study was to explore the optimal timing of radiotherapy in EGFR-TKI treated non-small cell lung cancer and the potential mechanism of changing the progression of drug resistance based on the clinical phenomena and the results of clinical trials.Methods:Through the collection,collation and analysis of clinical trial data,the effect of radiotherapy on postponing acquired resistance of EGFR-TKI was studied.Animal models were established,and in vivo experiments were conducted to simulate acquired drug resistance and the involvement of radiotherapy in the treatment process of EGFRTKI at different times,and to analyze and explore the influence of different timing of radiotherapy on acquired drug resistance and the influence on tumor growth.To explore the changes of intracellular signaling pathways induced by radiotherapy combined with EGFR-TKI,a drug-resistant strain of EGFR-TKI sensitive cells was constructed in cell model.In addition,RNA-seq sequencing was performed on tumor samples obtained from animal experiments to screen genes that differed between groups before and after acquired drug resistance combined with radiotherapy,and functional verification was performed at animal and cellular levels.Result:The existing results of clinical trials at the present stage indicate that when EGFR-TKI has the best efficacy.About 3 months after treatment,combined radiotherapy can effectively prolong patients’ PFS and delay the onset of acquired resistance.Animal experiments have proved that the combination of radiotherapy and EGFR-TKI at the early stage of administration can significantly inhibit tumor transplantation in mice.The differential genes screened by RNA-seq for morning and evening radiotherapy were mainly in the pro-apoptotic protein BIM and the proto-oncogene Fos family,among which the expression difference of transcription factor c-Fos was the most significant.Through the detection of c-Fos expression in cell and animal tumor samples,it was verified that combined radiotherapy could down-regulate the expression level of c-Fos in tumors,while the expression of BIM was significantly increased.The acquired resistance of EGFR-TKI sensitive strains was constructed,and the c-Fos was silenced in the resistant cell lines.It was verified that the change of c-Fos expression level affected the resistance status of EGFR-TKI.Conclusion:Combined radiotherapy can effectively delay acquired drug resistance,while EGFRTKI has the best efficacy in non-small cell lung cancer.In EGFR-TKI treatment,combined radiotherapy can reduce the expression level of transcription factor c-FOS in cancer cells.The regulation of c-FOS expression level on BIM may be the potential molecular mechanism of radiotherapy to delay acquired drug resistance in NSCLC cells.