Cyclin K Interacts With β-catenin To Induce Cyclin D1 Expression And Facilitates Tumorigenesis And Radioresistance In Lung Cancer

Objective: Lung cancer is one of the malignant tumors that seriously affect human health.Radiotherapy is an important treatment for patients with early and locally advanced lung cancer who are unable or unwilling to undergo surgery,and can also improve survival in advanced lung cancer.However,the 5-year survival rate after radiotherapy for lung cancer is less than satisfied,and it is still a key problem to improve the effectiveness of radiotherapy for lung cancer.Therefore,it is of great theoretical and clinical significance to study the molecular mechanism of radiotherapy resistance of lung cancer and provide sensitizing targets for radiotherapy.Recent studies have shown that Cyclin K is involved in the regulation of genomic stability,but the biological function of Cyclin K in lung cancer and whether it affects the radiotherapy sensitivity of lung cancer cells have not been reported.The purpose of this study was to investigate the function and mechanism of Cyclin K in lung cancer.Methods: We explored the difference of the expression of Cyclin K mRNA in lung cancer and paracancer.The relationship between Cyclin K expression and prognosis of lung cancer patients was studied by immunohistochemical staining and survival analysis.Cyclin K expression in human normal lung epithelial cells and lung cancer cell lines was analyzed by Western blot.We researched the effects of Cyclin K on the growth and proliferation of lung cancer cells by targeting the silencing of Cyclin K by siRNA and shRNA,as well as the effect of Cyclin K on radiotherapy induced G2/M phase block,the change of proportion in M phase after radiotherapy and the foci of γ-H2 AX.The effect of Cyclin K on radiotherapy sensitivity of lung cancer was investigated by clony formation experiment and verified at the animal level.RNA-seq technology was used to find that Cyclin K was involved in regulating Wnt pathway.Immunoprecipitation experiment was conducted to find that Cyclin K had an interaction with beta-catenin,and promoted the mRNA and protein expression of its downstream substrate Cyclin D1 by stabilizing the expression of beta-catenin.Rescue experiments proved that Cyclin K functions biologically dependent on Cyclin D1.Results: The high expression of Cyclin K in lung cancer was confirmed by the database,cell lines as well as the microarray staining of lung cancer.After silencing of Cyclin K,the growth and proliferation of lung cancer cell lines A549 and H460 were significantly slowed down.After radiotherapy,the proportion of G2/M phase cells decreased,while the proportion of M phase cells sensitive to radiotherapy increased,and radiotherapy resistance reduced.The results of animal experiments also showed that after targeted silencing of Cyclin K,the growth rate of transplanted tumor in nude mice was slowed down and the resistance to radiotherapy was decreased.Transcriptome sequencing confirmed the involvement of Cyclin K in the WNT pathway,and immunoprecipitation experiments confirmed the interaction between Cyclin K and beta-catenin,and that Cyclin K enhanced the stability of beta-catenin,and subsequently upregulated the expression of Cyclin D1.Rescue experiments proved that Cyclin K functions biologically dependent on Cyclin D1.Conclusion: Cyclin K expression was upregulated in lung cancer cell lines,and tissue microarray analysis showed that Cyclin K expression was negatively correlated with prognosis of lung cancer patients.Cyclin K interacts with beta-catenin to improve the stability of beta-catenin and up-regulate Cyclin D1 expression,thus increasing radiotherapy resistance of lung cancer cells.