Tumor Necrosis Factor Receptor-Associated Factor 4 (TRAF4) is a gene whose expression is altered in cancers. It is overexpressed in a variety of carcinomas of different origins, often as a consequence of amplification. TRAF4 encodes an adaptor protein that belongs to the TRAF protein family. While most TRAF proteins influence immune and inflammation processes, TRAF4 is mainly involved in developmental and morphogenic processes. Interestingly, this protein has been shown to be linked to crucial cellular functions such as cell polarity and the regulation of reactive oxygen species production.