Novel signaling pathways in breast cancer

Aberrant signaling is a key characteristic of cancerous cells that frequently leads to continuous proliferation and suppressed apoptosis. To correct deregulated signaling pathways and thereby eliminate cancer cells, many biological and chemical agents have been developed and used for breast cancer therapy that specifically target oncogenic signaling molecules. In the past two decades, significant advances have been made in the prevention, diagnosis, and treatment of breast cancer that can be attributed largely to the identification and understanding of the aberrant signaling network critical in the development and progression of breast tumors. These pathways include those of the ErbB family of receptor tyrosine kinases (RTKs), estrogen receptors (ERs), BRCA1/2, c-myc, TGF-a, and Wnt [1, 2]. However, to further accelerate the development of more efficient therapy for breast cancer, there is a continuous and urgent need for a better understanding of the malignant, chemoresistant, and metastatic biology of breast tumors. Specifically, to best fulfill this need, we will require to: (1) gain knowledge about the biological activities of the aberrant signaling network, (2) identify and characterize novel signaling modules important for mammary glands, and (3) fully address the complexity (i.e., pathway crosstalk), of the oncogenic signaling pathways. The goal of this chapter, therefore, aims to describe recent research findings in all three of these aspects of signaling pathways, focusing on their involvement in breast cancer development, progression, and metastasis.