Downregulation of <scp>SUN2</scp> promotes metastasis of colon cancer by activating <scp>BDNF</scp> / <scp>TrkB</scp> signalling by interacting with <scp>SIRT1</scp>
Lijuan Liu, Si‐Wei Li, Wenxin Yuan, Jianjun Tang, Yi Sang
Abstract
Distant metastasis is the major cause of colon cancer (CC) treatment failure. SAD1/UNC84 domain protein-2 (SUN2) is a key component of linker of the nucleoskeleton and cytoskeleton (LINC) complexes that may be relevant for metastasis in several cancers. Here, we first confirmed that SUN2 levels were significantly lower in primary CC tissues and distant metastasis than in normal colon tissues, and high SUN2 expression predicted good overall survival. Overexpression of SUN2 or knockdown of SUN2 inhibited or promoted cell migration and invasion in vitro, respectively. Moreover, silencing of SUN2 promoted metastasis in vivo. Mechanistically, we showed that SUN2 exerts its tumour suppressor functions by decreasing the expression of brain derived neurotrophic factor (BDNF) to inhibit BDNF/tropomyosin-related kinase B (TrkB) signalling. Additionally, SUN2 associated with SIRT1 and increased the acetylation of methyl-CpG binding protein 2 (MeCP2) to increase its occupancy at the BDNF promoter. Taken together, our findings indicate that SUN2 is a key component in CC progression that acts by inhibiting metastasis and that novel SUN2-SIRT1-MeCP2-BDNF signalling may prove to be useful for the development of new strategies for treating patients with CC. © 2021 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.