Breast cancer continues to be the most commonly diagnosed cancer and one of the leading causes of cancer death in women in Canada, as well as worldwide. Breast cancer is not a single disease; it is made up of several subtypes that have distinct molecular characteristics and clinical outcomes. In our project we study one of these subtypes, triple-negative breast cancer that is more commonly diagnosed in younger women. It is the most aggressive form of breast cancer with extremely poor prognosis. For triple-negative breast cancer, chemotherapy remains the main therapeutic option. However, tumors that initially respond to chemotherapy often eventually develop resistance. Previous studies have shown that in response to stress (such as chemotherapy or radiation therapy) cancer cells activate a process called autophagy ("self-eating"). Autophagy helps cancer cells survive stressing conditions, and therefore is considered to be one of the mechanisms of drug resistance. In our study we are using cell lines and mice models to find out whether by blocking autophagy in triple-negative breast cancer cells we can enhance therapeutic response and overcome treatment resistance. We are aiming to propose a new strategy in the treatment of triple-negative breast cancer.