Immune-Endocrine Perspectives of Breast Cancer

Abstract

Cancer is the consequence of the recalcitrant multiplication of the transformed cells. Cancer cells grow and proliferate at a fast pace and do not follow normal regulation of cell division. Breast cancer is a heterogeneous group of diseases, which is the second leading cause of death among women. Although androgen is primarily considered a male steroid hormone, it also has an important role in the female reproductive system. The literature evidence suggests the role of androgen receptors (AR) in the normal development of the breast. At puberty, the expression of AR is even more than ER, suggesting its importance during the process of sexual development; its activity maintains the ER-induced cell proliferation and normal development of the breast. Epidemiological studies have suggested a positive correlation between high endogenous androgens and the risk of breast cancer in both pre- and postmenopausal women. In both ER and PR-positive breast cancers, AR is expressed in 60-70% of the cases. AR is also reported to be co-expressed with ER in around 80-90% of breast cancer cases and is considered an independent prognostic factor of ER-positive breast cancers. Tumor-microenvironment has a complex role in tumor initiation, progression, and metastasis. Tumor-infiltrating and resident cells secretes a variety of inflammatory and anti-inflammatory cytokines, which in turn either inhibit or promote tumor growth. Immunosuppressive and immuno-inductive effects of androgen have been reported in various studies. Androgens have been reported to influence the adaptive immune system more than the innate immune system in many ways. Crosstalk of androgen and cytokine signaling has many effects in breast cancer epidemiology. So, in this chapter, we will discuss the various immune-endocrine perspectives of breast cancers.