Downregulation of SAFB Sustains the NF-κB Pathway by Targeting TAK1 during the Progression of Colorectal Cancer

Purpose: To investigate the role and the underlying mechanism of scaffold attachment factor B ( SAFB ) in the progression of colorectal cancer (CRC). Experimental Design: SAFB expression was analyzed in the Cancer Outlier Profile Analysis of Oncomine and in 175 paraffin-embedded archived CRC tissues. Gene Ontology analyses were performed to explore the mechanism of SAFB in CRC progression. Western blot, RT-PCR, luciferase assay, and chromatin immunoprecipitation (ChIP) were used to detect the regulation of transforming growth factor-β–activated kinase 1 ( TAK1 ) and NF-κB signaling by SAFB . The role of SAFB in invasion, metastasis, and angiogenesis was investigated using in vitro and in vivo assays. The relationship between SAFB and TAK1 was analyzed in CRC tissues. Results: SAFB was downregulated in CRC tissues, and low expression of SAFB was significantly associated with an aggressive phenotype and poorer survival of CRC patients. The downregulation of SAFB activated NF-κB signaling by targeting the TAK1 promoter. Ectopic expression of SAFB inhibited the development of aggressive features and metastasis of CRC cells both in vitro and in vivo . The overexpression of TAK1 could rescue the aggressive features in SAFB-overexpressed cells. Furthermore, the expression of SAFB in CRC tissues was negatively correlated with the expression of TAK1- and NF-κB–related genes. Conclusions: Our results show that SAFB regulated the activity of NF-κB signaling in CRC by targeting TAK1 . This novel mechanism provides a comprehensive understanding of both SAFB and the NF-κB signaling pathway in the progression of CRC and indicates that the SAFB–TAK1–NF-κB axis is a potential target for early therapeutic intervention in CRC progression. Clin Cancer Res; 23(22); 7108–18. ©2017 AACR .