Vanillic Acid Improves Comorbidity of Cancer and Obesity through STAT3 Regulation in High-Fat-Diet-Induced Obese and B16BL6 Melanoma-Injected Mice

Obesity is known to be associated with risk and aggressiveness of cancer. Melanoma, the most lethal type of skin cancer, is also closely related to the prevalence of obesity. In this study, we established a cancer-obesity comorbidity (COC) model to investigate the effects of vanillic acid (VA). After a five-week administration with a high-fat diet (HFD) to induce obesity, subcutaneous allograft of B16BL6 cells were followed, and VA was orally administrated for an additional two weeks. VA-fed mice showed significantly decreased body weight and white adipose tissue (WAT) weight, which were due to increased thermogenesis and AMPK activation in WATs. Growth of cancer was also suppressed. Mechanistic studies revealed increased apoptosis and autophagy markers by VA; however, caspase 3 was not involved. Since signal transducer and activator of transcription 3 (STAT3) is suggested as an important pathway linking obesity and cancer, we further investigated to find out if STAT3 phosphorylation was repressed by VA treatment, and this was again confirmed in a COC cell model of adipocyte conditioned medium-treated B16BL6 melanoma cells. Overall, our results show VA induces STAT3-mediated autophagy to inhibit cancer growth and thermogenesis to ameliorate obesity in COC. Based on these findings, we suggest VA as a candidate therapeutic agent for COC treatment.