Cellular and Molecular Mechanisms of Breast Cancer Progression

Breast cancer is a common death-related cancer in women globally. Early and non-metastatic stage breast cancers are curable in 70-80% of the patients, while advanced-stage distant organ metastatic breast cancers are incurable with present treatment options. Although multiple risk factors are associated with breast cancer, among them, genetic predispositions in BRCA1 and BRCA2 genes are the most causative factor for breast cancer malignancy. The initiation and progression of breast cancer is a multi-step process, which can initiate either in ducts or lobules of the breast tissues. As time progresses pre-invasive lesions form of breast neoplasm transforms into atypical ductal hyperplasia (ADH), ductal carcinoma in situ (DCIS)/lobular carcinoma in situ (LCIS), and eventually become invasive carcinoma. The molecular mechanisms behind the initiation and progression of breast cancer are not completely understood. However, epithelial-mesenchymal transition (EMT) is the assurance of malignancy which disrupts endothelial integrity and therefore, it increases the spreading of cancer cells and facilitates metastasis. After the epithelial-mesenchymal transition of tumor cells, tumor cells invade and migrate the neighboring as well as distant tissues, cross the endothelial barrier and enter the blood, and attach to a secondary site, forming metastases. In this chapter, we have reviewed an overview of the molecular mechanisms of breast cancer progression.