Origins and Actions of Tumor Necrosis Factor α in Postmenopausal Breast Cancer

Tumor necrosis factor alpha (TNF alpha) has many roles in both physiological and pathological states. Initially thought to cause necrosis of tumors, research has shown that in many tumor types, including breast cancer, TNF alpha contributes to growth and proliferation. The presence of TNF alpha-derived from the tumor and infiltrating immune cells-within a breast tumor microenvironment has been correlated with a more aggressive phenotype, and the postmenopausal ER+ subtype of breast cancers appears to strongly respond to its many pro-growth signaling functions. We discuss how TNF alpha regulates estrogen biosynthesis within the breast, affecting the activity of the key estrogen-synthesizing enzymes aromatase, estrone sulfatase, and 17 beta-HSD type 1. Additionally, we describe the anti-adipogenic actions of TNF alpha that are critical in preventing adjacent estrogen-producing adipose fibroblasts from differentiating, ensuring that the tumor maintains a constant source of estrogen-producing cells. We examine how the increased risk of developing breast cancer in older and obese individuals may be linked to the levels of TNF alpha in the body. Finally, we evaluate the feasibility of targeting TNF alpha and its associated pathways as a novel approach to breast cancer therapeutics.