White Adipose Tissue Browning and Cancer Cachexia

Cachexia or wasting syndrome is often seen in cancer patients. Over half of the patients suffer from this condition although the incidence varies from tumor types. Symptoms of cancer cachexia include progressive weight loss, anorexia, depletion of adipose tissues and loss of skeletal muscle mass. Treatment with nutrient supplements or appetite stimulants often fails to reverse these metabolic abnormalities. Thus far, the exact mechanism in which how cancer causes cachexia is poorly understood. One hypothesis is that tumors secrete factors to induce protein degradation in skeletal muscles and enhance lipolysis in adipocyte tissues. Concordantly, early studies have shown that animal models with tumor removal reverse these metabolic symptoms. Thus, there is a mounting interest of identifying these tumor-derived factors, which may aid the development of new therapeutic interventions. Recently, new findings have shed new light into this strenuous area in which parathyroid hormone related protein (PTHrP) [1] and Interlukin-6 (IL-6) [2] have been found to be inducer for cancer cachexia. Both factors have important biological functions for many well-known processes.For instance, PTHrP plays critical roles during fetal development and postnatal epithelial differentiation [3]. In Particular, PTHrP is an important factor to regulate cartilage and bone homeostasis [4].