ABSTRACT
Breast tumors develop within a specialized tumor microenvironment that consists of numerous cell types, including cancer cells, stromal cells, adipose tissue, and infi ltrating immune cells. Th ese cells release a wide range of factors that can modulate tumor development by regulating cancer cell proliferation, survival, invasion and motility, as well as local blood vessel formation, or angiogenesis. In particular, cytokines are highly expressed in the breast tumor microenvironment and can play a crucial role in many of these processes during breast tumorigenesis. Cytokines also appear to be important in breast tumor metastasis, particularly to the bone, where cytokines are abundantly expressed. Interestingly, the eff ects of cytokines can be pro-tumorigenic and lead to enhanced tumor development and progression to a more aggressive disease, or anti-tumorigenic with reduced tumor growth and inhibition of tumor angiogenesis. Furthermore, the eff ects of cytokines can result from both modulation of the immune system and direct eff ects of cytokines on the tumor itself, independent of the immune system. Th e direct eff ects, rather than the immuno-modulatory eff ects, of cytokines on breast tumor growth, invasion, and metastasis are the focus of this chapter.
