Expression of Toll-Like Receptors on Breast Tumors: Taking a Toll on Tumor Microenvironment

Breast cancer remains a major cause of death in women in the developed world. As Toll-like receptors (TLRs) are widely expressed on tumor cells and play important roles in the initiation and progression of cancer, they may thus serve as important targets and have an effective perspective on breast cancer treatment. Expression of TLRs on breast cancer cells and mononuclear inflammatory cells can promote inflammation and cell survival in the tumor microenvironment. Inflammation and cancer are related. It is well known that persistent inflammatory conditions can induce cancer formation, due to production of cytokines and chemokines, which play a crucial role in promoting angiogenesis, metastasis, and subversion of adaptive immunity. TLR signaling in tumor cells can mediate tumor cell immune escape and tumor progression, and it is regarded as one of the mechanisms for chronic inflammation in tumorigenesis and progression. This paper delineates the expression of various TLRs in promotion of inflammation and development of mammary tumors. Understanding the mechanisms through which TLRs on breast cancer cells and inflammatory cells regulate growth, survival, and metastatic progression can make them potential targets for breast cancer therapy.