Type I Interferons as Joint Regulators of Tumor Growth and Obesity.

Type I interferons (IFN-I) are antiviral cytokines endowed with multiple biological actions, including antitumor activity. Studies in mouse models and cancer patients support the concept that endogenous IFN-I play important roles in the control of tumor development and growth as well as in response to several chemotherapy/radiotherapy treatments. While IFN-I signatures in the tumor microenvironment are often considered as biomarkers for a good prognostic response to antitumor therapies, prolonged IFN-I signaling can lead to immune dysfunction, thereby promoting pathogen or tumor persistence, thus revealing the "Janus face" of these cytokines in cancer control, likely depending on timing, tissue microenvironment and cumulative levels of IFN-I signals. Likewise, IFN-I exhibit different and even opposite effects on obesity, a pathologic condition linked to cancer development and growth. As an example, evidence obtained in mouse models shows that localized expression of IFN-I in the adipose tissue results in inhibition of diet-induced obesity, while hyper-production of these cytokines by specialized cells such as plasmacytoid dendritic cells in the same tissue, can induce systemic inflammatory responses leading to obesity. Further studies in mouse models and humans should reveal the mechanisms by which IFN-I can regulate both tumor growth and obesity and to understand the role of factors such as genetic background, diet and microbioma in shaping the production and action of these cytokines under physiological and pathological conditions.