Investigating The Association Between Autophagy And Epithelial To Mesenchymal Transition In Breast Cancer Cells Cultured Under The Hypoxic Condition

Abstract

Breast cancer has become one of the most burning issues in the world with very high death rate. Though many therapies and treatments have been developed, devising a method to alleviate the mortality rate of breast invasive cancer patients due to a low response to treatments of cancer cells still remain unanswered. Recently, it is found that the mechanism of epithelial-to-mesenchymal transformation (EMT), considered crucial in the initial stage of metastasis, makes it easier for breast cancer cells to leave the main tumor site and spread throughout the body. Moreover, the autophagy has been proved to induce the tumorigenesis by assisting the cancer-cell proliferation and tumor growth. Therefore, this study aimed to demonstrate the association between autophagy and EMT cultured under hypoxic conditions. The ����2 is used to mimic the hypoxic condition. We examined whether the hypoxic conditions facilitate the migration of breast cancer cells via the wound healing assay or not. Under the normoxia or hypoxia conditions, the expression of hypoxia-related genes (HIF-1, HIF-2), autophagy-related genes (LC3-II, Beclin-1) and EMT-related genes (Ncadherin, E-cadherin, Vimentin) were evaluated by the RT-qPCR. The 3- Methyladenine, an autophagic inhibitor, was used to evaluate the role of the autophagy in promoting the EMT in breast cancer cells. Breast cancer cells also demonstrated high expression level of hypoxia-related genes (HIF-1 and HIF-2), autophagy-related genes (LC3-II and Beclin-1) and EMT-related genes (N-cadherin, E-cadherin, and Vimentin) under hypoxic condition. The hypoxia-related gene (HIF- 1 and HIF-2) expression promoted the elevation of autophagy. Moreover, the migration and EMT gene expression was associated with the autophagy under the hypoxic condition. The result clearly showed a significant decline in migration and gene expression in hypoxic condition compared to normoxic condition. Hence, it was indicated that the autophagy has a specific role in assisting the metastasis ability of breast cancer cells. In addition, the stemness ability was revealed to grow in hypoxic condition, which is parallel to the breast cancer stem cell theory. As a result, the autophagy showed huge advantages of the therapeutic strategies targeted in reducing metastasis.