SOSTDC1 Inhibits Proliferation,Migration And Osteolytic Destruction Of Non-small Cell Lung Cancer

Background and objective:Lung cancer is one of the most common malignant tumors and is the main cause of cancer death.The 5 year survival rate of patients with lung cancer was only 16.6%.About 85% of the lung cancer are non-small cell lung cancer,and the pathological types are usually adenocarcinoma,squamous cell carcinoma and large cell carcinoma.The incidence of bone metastases in non-small cell lung cancer is up to 40%,which seriously affects the patient’s living ability and mortality.Bone metastasis can cause severe pain,pathologic fractures,spinal cord compression,hypercalcemia,which were associated with poor quality of life,low survival rate and heavy medical expenses burden.The study of molecular mechanism of bone metastasis in non-small cell lung cancer can provide us new methods to cure this disease which may improve the quality of life and save medical expenses,Sclerostin domain-containing protein 1(SOSTDC1),also known as WISE,USAG1 and ectodin,has been studied in tooth development,hair follicle formation,limb morphology and trigeminal ganglion formation.As a regulator of cell differentiation and proliferation,SOSTDC1 has been found to be involved in the development of breast,gastric,renal and thyroid cancers.However,the role and mechanism of SOSTDC1 in metastasis of non-small cell lung cancer,especially in bone metastases,is still unclear.Therefore,we hope that by studying the mechanism of bone metastasis in non-small cell lung cancer,we will provide a new direction for prevention,diagnosis and treatment of bone metastases in non-small cell lung cancer.Research contents and methods:First of all,we enrolled patients with non-small cell lung cancer tissues from January 2009 to December 2015,who underwent surgery in the Second Affiliated Hospital of Second Military Medical University 145 cases of non-small cell lung cancer,141 cases of tumor adjacent tissues and 49 cases of metastatic bone of non-small cell lung cancer were collected.The clinical data of patients were collected,including age,sex,tumor size,AJCC staging and pathological results.SOSTDC1 expression in NSCLC primary tumor,tumor adjacent tissues and bone metastatic tissueswere detectedby immunohistochemistry and qRT-PCR,the correlationship between SOSTDC1 expression and prognosis of patients with NSCLCwas studied.Then,we overexpressed or inhibited SOSTDC1 in A549 and PC9 cells.PCR and Western-blot test were used for verifing the transfection efficiency,and through CCK8 assay,Transwell test and osteoclast differentiation experiments,the role of SOSTDC1 in the proliferation,migration and invasion of NSCLC and the differentiation of osteoclast induced by NSCLC were studied.Finally,we used RNA deep sequencing for finding the genes that were responsive to SOSTDC1 overexpression in PC9 cell.We explored possible downstream pathways through GO analysis and pathway analysis,and verified the regulation role of SOSTDC1 on downstream gene expression by qRT-PCR.Results:Our study found that compared with primary tumors,SOSTDC1 expression was downregulated in patients with bone metastases of NSCLC.further study found that SOSTDC1 expression was a poor prognostic factor in NSCLC.Over expression of SOSTDC1 can inhibit the proliferation,migration and invasion of NSCLC cells and the osteoclast induced by cancer cells,vice verse.In addition,through NSCLC RNA deep sequencing and qRT-PCR we identified the related downstream genes of SOSTDC1,including PAK6,CCL3,BTG,WNT10 A,CXCL1,CXCL2,CXCL8 and CXCL10.These genes was regulated by SOSTDC1,thus playing a significant role in NSCLC proliferation,migration,invasion and distant metastasis Conclusion:Accordingly,we suggest that SOSTDC1 may transfer especially in NSCLC play an important role in the process of bone metastasis,SOSTDC1 can inhibit NSCLC proliferation,migration,invasion,and can inhibit the osteoclast differentiation by regulating the related downstream genes including PAK6,CCL3,BTG,WNT10 A,CXCL1,CXCL2,CXCL8 and CXCL10 genes in NSCLC cells.These results suggest that SOSTDC1 may play an important role in the process of bone metastasis of NSCLC,provides a new explanation for bone metastasis of non-small-cell lung cancer pathogenesis,and SOSTDC1 may be a potential prognostic marker and new therapeutic target for bone metastases in NSCLC.