Downregulation Of MTDH Via SiRNA Inhibites Malignant Biological Behaviors Of Breast Cancer Cells

Breast cancer is the most common malignancy and the leading cause of cancer death in females worldwide. Increasing evidence manifests that breast cancer possesses a high heterogeneity. Breast cancer of varied molecular expression profiles exhibits different response to certain treatment and varies greatly in disease outcome and prognosis. Both HER2overexpressing and triple-negative breast cancer are associated with a relative poor prognosis as exemplified by a higher incidence of recurrence and metastasis. Except for optimizing existing treatments, new molecular targets are in great need of investigation to manage these subtypes of aggressive breast cancer.Metadherin (MTDH) also known as Astrocyte Elevated Gene-1(AEG-1), is emerging as an oncogene that closely correlates with cancer genesis and progression. MTDH activates multiple signal transduction pathways that promote cell transformation and plays an important role in aggressive phenotypes of cancer, including unlimited proliferation, evasion of apoptosis, invasion, metastasis, angiogenesis and chemoresistance, etc. Recent studies indicate that MTDH is overexpressed in breast cancer and is correlated with poor prognosis. It is thus necessary to explore its functional role in aggressive hallmarks of breast cancer and to investigate its possibility of acting as a potential therapeutic target in breast cancer.In the present study, we employed siRNA to reduce MTDH expression in human SK-BR-3and MDA-MB-453cell lines, which typically exemplify HER2overexpressing and triple-negative breast cancer cells respectively, and observed the influence of MTDH downregulation on the malignant biological behaviors in breast cancer. We hope this study can provide some theoretical and experimental basis to establish MTDH as a potential therapeutic target in breast cancer of unfavorable prognosis.Part1Knockdown of MTDH inhibits proliferation and induces apoptosis in human breast cancer SK-BR-3cellsObjective:To investigate the effects of MTDH downregulation on cell proliferation and apoptosis in breast cancer SK-BR-3cells.Methods:siRNA was employed to reduce MTDH expression in human breast cancer SK-BR-3cells. Reverse transcription PCR and immunocytochemistry were applied to identify the downregulation of MTDH. MTT assay was performed to assess SK-BR-3cell proliferation, flowcytometry was employed to detect cell cycle and apoptosis.Results:Knockdown of MTDH could inhibit cell proliferation and induce cell apoptosis. MTDH downregulation resulted in accumulation of the G0/G1phase cell and reduction of S and G2/M phase cell.Conclusion:Reduced MTDH expression in SK-BR-3cells could inhibit cell proliferation and induce apoptosis.Part2Downregulation of MTDH inhibits adhesion, migration and invasion in human breast cancer MDA-MB-453cellsObjective:To investigate the effects of MTDH downregulation on cell adhesion, migration and invasion in human breast cancer MDA-MB-453cells.Methods:siRNA was employed to reduce MTDH expression in human breast cancer MDA-MB-453cells. Reverse transcription PCR and immunocytochemistry were applied to identify the downregulation of MTDH. Adhesion, migration and invasion assays were performed to assess its impact on the abilities of adhesion, migration and invasion in MDA-MB-453cells.Results:Knockdown of MTDH could inhibit cell adhesion, the adhesion rate at30min and60min were decreased by42.0%and49.7%compared with the control group. Cell migration was also inhibited, the migration rate were decreased by33.3%compared with the control group. Moreover, MTDH downregulation resulted in decreased invasiveness by46.3%.Conclusion:Reduced MTDH expression in MDA-MB-453cells could inhibit cell adhesion, migration and invasion.