Autophagy Promotes The Malignant Biological Behaviour Of Breast Cancer Cells By Influencing PTPMT1

【Backgrounds】 Breast cancer is one of the most common malignancies with the highest incidence and mortality in women among the world.Thanks to the great development of modern medical techniques,a therapy of surgery with chemotherapy and chemotherapy has been established,which greatly contributes to increase the five-year survival rate,but recurrence and metastasis of breast cancer still greatly threat the patient’s life.Recent studies have shown that the occurrence and development of breast cancer is associated with certain genes,our laboratory concerned about is PTPMT1.PTPMT1 is a PTEN-like tyrosine phosphatase encoded by nuclear DNA and widely distributed in mitochondria of various tissues.Previous studies in the laboratory suggest that PTPMT1 may play a role as a tumor suppressor in breast cancer.So we detected the expression of PTPMT1 at the level of m RNA and protein respectively in normal breast epithelial cells and breast cancer cells,but there was a big difference between the two results.We speculate on whether protein degradation occurred during this process and whether protein degradation is due to autophagy.Autophagy is a very common pathophysiological process in the body,which can satisfy cell’s own metabolic needs and the renewal of organelles.In recent years,autophagy has become an important issue in cancer research,but the relationship between autophagy and cancer is still in dispute.In order to explore the role of PTPMT1 in breast cancer and its possible mechanism of the difference in the expression of PTPMT1 between RNA and protein,we have transfected plasmid to change the expression of PTPMT1 in both normal breast epithelial cells and breast cancer cells and conducted a series of cell behavior experiments,which provides new ideas and clues for the clinical treatment of breast cancer.【Research Methods】 1.Detection of PTPMT1 in normal breast epithelial cells and breast cancer cell lines by RT-PCR and Western-Blot.2.Detection of marker of autophagy in normal breast epithelial cells and breast cancer cell lines by Western-Blot.3.Transfection with WT-PTPMT1 plasmid to up-regulate the expression of PTPTM1 in T47 D,then cell behavior experiments detected the effect of PTPMT1 on the cell malignant biological behavior.4.Transfection with Sh RNA plasmid to knock down the expression of PTPMT1 in both MCF-10 A and MCF-7,then cell behavior experiments detected the effect of PTPMT1 on the cell malignant biological behavior.5.Transfection with WT-PTPMT1 plasmid increased the expression of PTPTM1 in T47 D,then added chloroquine.The cell behavior experiments detected the effect of chloroquine on the malignant biological behavior,and the change of PTPMT1 expression was detected by Western-Blot.6.Transfection with Sh RNA plasmid knocked down the expression of PTPTM1 in MCF-10 A,then added chloroquine.The cell behavior experiments detected the effect of chloroquine on the malignant biological behavior,and the change of PTPMT1 expression was detected by Western-Blot.7.Bcl-2 expression was detected by Western-Blot after changing the expression of PTPMT1.【Experiment Results】 1.The results of RT-PCR showed that there was no significant difference in the expression of PTPMT1 between normal breast epithelial cells and breast cancer cells at the m RNA level.At the protein level,PTPMT1 expression in normal breast epithelial cells was significantly higher than that in breast cancer cells.2.The autophagy level of breast cancer cells was significantly higher than that of normal breast epithelial cells,and T47 D cells which had low expression of PTPMT1 showed stronger autophagy.3.Upregulation of PTPMT1 expression in T47 D reduced the malignant behavior such as migration,invasion and colony formation.4.Knockdown of PTPMT1 expression in MCF-10 A and MCF-7 increased the malignant behavior such as migration,invasion and colony formation.5.Chloroquine,an autophagy inhibitor,can increase the expression of PTPMT1 in T47 D cells,and can reduce the malignant behavior.6.Chloroquine,an autophagy inhibitor,can increase the expression of PTPMT1 in MCF-10 A cells which transfected with Sh RNA plasmid,and can also reduce the malignant behavior.7.Bcl-2 expression increased after PTPMT1 expression was up-regulated in T47 D cells and Bcl-2 expression decreased after knockdown of PTPMT1 expression in MCF-10 A cells.【Conclusion】 Low expression of PTPMT1 can promote the malignant behavior of breast cancer.Chloroquine,an autophagy inhibitor,can reverse malignant behavior of breast cancer and increase PTPMT1 expression.