| It has been well established that chromatin remodeling is critical for essentially all aspects of nuclear activities including transcription, DNA replication, and DNA damage repair,chromatin remodeling mainly refers to two kinds complexes, one is ATP-dependent chromatin remodeling complexes, the other is protein covalent modification associated complexes,such as histone acetylation and methylation enzyme and so on. ATP-dependent chromatin remodeling complexes contain certain subunits, which are thought to regulate transcription of certain genes By altering the chromatin structure around those genes, dysfunction of the subunits may cause aberrant chromatin remodeling activity which results in various diseases such as cancers,taken together with the previous study,we confirm several subunits are tumor suppressors.ARIDIA (AT-rich interactive domain-containing protein1A) is a large subunit of SWI/SNF complexes, and recent studies reveal that ARID1Ais frequently mutated incarcinomas arising from ovarian, liver, gastric and breast,ARID1A can repress cell proliferation by up regulating p21and SMAD3transcription,as well as inhabit repress cell proliferation mediated by PI3K/AKT pathway in glioma.ARID1A has a suppressive role in tumor metastasis in liver cancers with undefined mechanism.Though,ARID1A can suppress gastric cancer cells proliferation, the mechanism need to be further elucidated, and limited study has been carried out with breast cancer. Hence, the mechanism and function of ARID1A in gastric and breast cancers are left to be further elaborated.To evaluate the function of ARID1A during breast and gastric cancer progress, the ARID1A shRNA based lentivirus vector and the control vector are respectively transfected into breast and gastric cancer cells, series of assay reveal that sh-ARID1A transfected cells have stronger growth, invasion and metastasis ability than control vector transfected gastric cells, on the contrary, overexpression of ARID1A in breast and gastric cancer cells is sufficient to suppress cell proliferation, invasion and metastasis. Meanwhile,with ARID1A knockdown,the phosphorylation level of AKT is enhanced and p21protein expression is downregulated. Meanwhile, cell cycle is disturbed which the percentage of cells in the S-phase of cell cycle are reduced and the percentage of cells in the G2-phase of cell cycle are increased, at the same time, more cells undergo apoptosis. In gastric cancer, we observe cell size become larger as well as the increase of glucose consumption with ARID1A knockdown. All these results indicate ARID1A regulate cell proliferation by influencing Akt phosphorylation level and cell cycle. Together with breast cancer, microarray is carried out in HEMC cells (controland ARID1A knockdown),results reveal that associated genes which suppress metastasis such as LIFR,ZEB1are down-regulated as well as Wnt singal repressor WIF-1and Wnt associated genes are in the condition of abnormal activation.The analysis of Western Blotting reveals that the expression of β-catenin increases,mainly in nucleus, as we know, β-catenin is a critical molecular in Wnt pathway, which can interact with TCF/LEF TCF DNA binding element after localizing in nucleus to regulated target genes transcription. Focusing on the activity of TOP-Flash, Wnt transcription regulation enhance when ARID1A is downregulated. Western Blotting and qPCR analysis show that ARID1A knockdown results in Wnt downstream gene C-MYC and CYCLIND1up regulation in mRNA and protein level. In agreement with previous reports, the activation of β-catenin/Wnt can promote breast cancer metastasis, consequently,ARID1A may repress metastasis by P-catenin/Wnt pathway.To extrapolate the aforementioned in vitro findings to an in vivo setting, we establish tumor xenografts in athymic nu/nu mice, we investigate Bcap-37Sh-ARIDIA cell have stronger tumorigenesis accompanied with enhanced proximal metastasis ability as compared to control cell. In Stably ARID1A knockdown gastric cancer cell lines,E-cadherin is downregulated, the capability of migration and infiltration are strengthened. Solely knocking out E-cadherin,cell migration and infiltration are still enhanced, qPCR analysis reveals E-cadherin mRNA decrease with ARID1A knockdown,we speculate ARID1A associated SWI/SNF complex collaborate transcription factors to regulate E-cadherin, Dual luciferase reporter gene assay shows, E-cadherin promoter activity decreased with ARID1A knockdown. Taken together with all our study, ARID1A modulate E-cadherin transcription to regulate tumor migration and infiltration in gastric cancer. To further clarify the relationship between ARID1A expressions in gastric clinical samples, we performed immunohistochemical analyses of189paired cancerous and noncancerous tissues. Results revealed decreased ARID1Aexpression in most tumor-bearing tissues compared with the matched adjacent non-tumor tissues,ARID1A loss is a malignant predictor which can cause gastric carcinogenesis, local lymph node metastasis and tumor infiltration. We verify that the ARID1A expression was significantly correlated with the expression of E-cadherin. In conclusion, in breast and gastric cancer,ARID1A mediate cell proliferation by regulating Akt phosphorylation and cell cycle.In breast cancer,ARID1A may collaborate Wnt/β-catenin pathway to suppress tumor migration and infiltration.When it refers to gastric cancer cell lines,ARID1A modulate migration and infiltration dependent on E-cadherin. |
