Cancer and heterogeneity of obesity: a potential contribution of brown fat.

Obesity has lately been drawing additional attention as a potential cancer risk and, with some exceptions as a prognostic factor. As obesity is a complex issue characterized by different variants, mechanisms and manifestations, its role in cancer development is also a complex problem exceeding the basic fact of the fat content rising above certain limits. Therefore, in the present paper obesity is viewed as a heterogeneous entity, which has distinct connections with cancer pathogenesis. Among other issues, emphasis is made on the state of white and brown adipose tissue, in particular the association of specific brown fat features and the so-called white fat browning with the functions of normal and mutated tumor suppressor genes, such as PTEN and BRCA1. These connections are considered from the viewpoint implying the existence of two types of hormonal carcinogenesis and of hormonal mediation of the genetic predisposition to tumor development, and should be accounted for in prevention and treatment of both obesity and cancer.