Transforming Growth Factor-β Superfamily: Evaluation as Breast Cancer Biomarkers and Preventive Agents

The Transforming Growth Factor-β (TGFβ) superfamily of cytokines is comprised of a number of structurally-related, secreted polypeptides that regulate a multitude of cellular processes including proliferation, differentiation and neoplastic transformation. These growth regulatory molecules induce ligandmediated hetero-oligomerization of distinct type II and type I serine / threonine kinase receptors that transmit signals predominantly through receptor-activated Smad proteins but also induce Smad-independent pathways. Ligands, receptors and intracellular mediators of signaling initiated by members of the TGFβ family are expressed in the mammary gland and disruption of these pathways may contribute to the development and progression of human breast cancer. Since many facets of TGFβ and breast cancer have been recently reviewed in several articles, except for discussion of recent developments on some aspects of TGFβ, the major focus of this review will be on the role of activins, inhibins, BMPs, nodal and MIS-signaling in breast cancer with emphasis on their utility as potential diagnostic, prognostic and therapeutic targets.