Tob negatively regulates NF-κB activation in breast cancer through its association with the TNF receptor complex

NF-κB mediates transcriptional regulation crucial to many biological functions, and elevated NF-κB activity leads to autoimmune and inflammatory diseases, as well as cancer. Since highly aggressive breast cancers have few therapeutic molecular targets, clarification of key molecular mechanisms of NF-κB signaling would facilitate development of more effective therapy. In this report, we show that Tob, a member of the Tob/BTG family of antiproliferative proteins, acts as a negative regulator of the NF-κB signal in breast cancer. Studies with 35 human breast cancer cell lines reveal that Tob expression is negatively correlated with NF-κB activity. Analysis of The Cancer Genome Atlas (TCGA) database of clinical samples reveals an inverse correlation between Tob expression and NF-κB activity. Tob2, another member of the Tob/BTG family, shows no such negative correlations. Furthermore, in TNF-α treated cells, Tob associates with TNF receptor complex I to suppress polyubiquitylation of RIPK1, which results in repression of NF-kB activity. Therefore, Tob functions as a negative regulator of the NF-κB pathway and may serve as a therapeutic target for aggressive breast cancer.