SIRT2 Inhibition by AGK2 Promotes Perinuclear Cytoskeletal Organisation and Reduces Invasiveness of MDA-MB-231 Triple-Negative Breast Cancer Cells in Confined In Vitro Models

Triple-negative breast cancer (TNBC) is a highly aggressive breast cancer subtype characterised by the absence of targetable hormone receptors and increased metastatic rates. As nuclear softening strongly contributes to TNBC's enhanced metastatic capacity, increasing the nuclear stiffness of TNBC cells may present a promising therapeutic avenue. Previous evidence has demonstrated the ability of Sirtuin 2 (SIRT2) inhibition to induce cytoskeletal reorganisation, a key factor in regulating nuclear mechanics. Thus, our study aimed to investigate the effect of SIRT2 inhibition on the nuclear mechanics and migratory behaviour of TNBC cells. To achieve this, SIRT2 was pharmacologically inhibited in MDA-MB-231 cells using AGK2, a SIRT2-specific inhibitor. Although SIRT2 inhibition had no effect on LINC complex composition, the AGK2-treated MDA-MB-231 cells displayed more prominent perinuclear organisations of acetylated alpha-tubulin, vimentin, and F-actin. Additionally, the nuclei of the AGK2-treated MDA-MB-231 cells exhibited greater resistance to collapse under osmotic shock. Scratch-wound assays also revealed that SIRT2 inhibition led to polarity defects in the MDA-MB-231 cells, while in vitro space-restrictive invasion assays highlighted their reduced migratory capacity upon AGK2 treatment. Taken together, our findings suggest that SIRT2 inhibition promotes a perinuclear cytoskeletal organisation in MDA-MB-231 cells, which enhances their nuclear rigidity and impedes their invasion through confined spaces in vitro.