| Backgroud: Lung cancer is the leading cause of cancer-related deaths in the world.Despite significant advances in the early detection and treatment of the disease,the prognosis remains poor,with an overall 5-year survival rate ranging from 15% to 20%.The main causes of poor prognosis of lung cancer are postoperative recurrence and tumor metastasis,in addition to the inoperable diagnosis.Although some progress has been made in molecular targeted therapy,the current tumor targeted drugs are mainly aimed at the active mutations of oncogenes,and there is still a lack of targeted treatment strategies for the inactive mutations of oncogenes or the mutations of tumor suppressor genes.In tumors,PARP inhibitors are used to treat BRCA1/2 mutant cells as a perfect model of "synergistic lethal" therapy,which is limited to BRCA1/2 mutation.However,BRCA1/2 mutations are rare in most tumors.The vast majority of tumors have both genetic and epigenetic abnormalities which can interact with each other to promote the occurrence and development of tumors.Similar to the inactivation mutations of tumor suppressor genes,epigenetic silencing of tumor suppressor genes can lead to functional loss of the signaling pathways in which they are involved.The successful application of the "synergistic lethal" strategy based on BRCA1/2 mutation provides a new opportunity and a wider application prospect for synergistic lethal therapy based on epigenetic abnormalities.Some tumor-related signaling pathways,such as ERK,PI3K/Akt,Wnt and other signaling pathways,are involved in DNA damage repair by directly participating in or affecting cell cycle.Studies have reported that TMEM176 A is frequently methylated in liver cancer,and epigenetic silencing TMEM176 A can activate ERK signaling pathway.ERK signaling pathway is a positive regulator of ATM-dependent homologous recombination repair.Therefore,the application of the‘BRCAness principle’ and the abnormal epigenetic changes in tumors is expected to obtain more novel strategies of "synergistic death".Methods ＆ Materals: In order to study the mechanism of action of TMEM176 A in lung cancer,nine lung cancer cell lines and 123 lung cancer tissue samples were used in the experiment.Methylation and expression of TMEM176 A in lung cancer cells and lung cancer were analyzed by methylation specific PCR and immunohistochemistry.MTT assay,clonal formation,invasion and migration,flow cytometry and xenograft mouse models were used to analyze the role and mechanism of TMEM176 A in lung cancer cells.Results: The Cancer Genome Atlas（TCGA）database was employed to explore expression of TMEM176 A is regulated by promoter region methylation.The expression of TMEM176 A was found to be regulated by promoter region methylation in lung cancer cells.TMEM176 A was methylated in 53.66%（66/123）of primary lung cancer.No association was found between TMEM176 A methylation and age,gender,alcohol abuse,smoking,tumor size,lymph node metastasis,differentiation and TNM stage（all P>0.05）.Reduced expression of TMEM176 A was associated with promoter region methylation in 40 cases of matched lung cancer and adjacent tissue samples（P<0.05）.Lower level expression of TMEM176 A was found in 30 cases of cancer tissue samples.Among the 30 cases that had reduced expression of TMEM176 A,20 cases were methylated.The reduced expression of TMEM176 A was significantly associated with promoter region methylation.In vitro experiments showed that TMEM176 A could inhibit the proliferation,clone formation,migration and invasion of lung cancer cells,induce cell arrest in G2/M phase,and induce cell apoptosis.TMEM176 a can inhibit the growth of lung cancer cells by inhibiting the ERK signaling pathway.In vivo experiments further confirmed that TMEM176 A could inhibit tumor formation in xenograft mice.In vivo and in vitro,TMEM176 A was found to inhibit the growth of lung cancer cells by inhibiting ERK signaling pathway.H1299 and H23 cells were sensitive to ATM inhibitor AZD0156.After TMEM176 A was knocked down in H727 cells expressing TMEM176 A with si RNA,the cells were sensitive to ATM inhibitor AZD0156.Conclusion: TMEM176 A is frequently methylated in human lung cancer,and the expression of TMEM176 A is regulated by promoter region methylation.TMEM176 A suppresses lung cancer growth by inhibiting ERK signaling.Methylation of TMEM176 A is a potential lung cancer diagnostic marker and a novel synthetic lethal therapeutic marker for AZD0156,an ATM inhibitor. |
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