IL-6, cancer and cachexia: metabolic dysfunction creates the perfect storm

Interleukin-6 (IL-6) is a pleiotropic cytokine with a wide range of biological actions including immune function, metabolism, hematopoiesis, and oncogenesis (1,2). IL-6 can have both pro and anti-inflammatory functions depending on the condition. Initially, IL-6 was believed to be pro-inflammatory because several inflammatory-based disorders such as infection, diabetes and obesity commonly show an increase in circulating IL-6 (3-5). In contrast, transient expression of IL-6 after exercise can have anti-inflammatory and insulin sensitizing effects (3,6,7). Despite its enigmatic biology, IL-6 has been heavily investigated for its role in the progression of cancer and cancer-associated cachexia (8). The recent publication from Flint et al. (9) adds supporting evidence that IL-6 regulates these processes through direct and indirect targeting of multiple systems leading to alterations in metabolism and endocrine function.