Perinuclear assembly of vimentin intermediate filaments induces cancer cell nuclear dysmorphia.

Nuclear dysmorphia, characterized by crumpled or lobulated polymorphic nuclear shapes, has been used as an index for the malignant grades of certain cancers. The expression of vimentin, a type-III intermediate filament protein, is a hallmark of the epithelial-to-mesenchymal transition. However, it remains unclear whether vimentin is involved in cancer cell nuclear dysmorphia. In this study, we found that vimentin intermediate filaments (VIFs) frequently accumulated at the concave of dysmorphic nucleus in breast cancer MDA-MB-231 cells. Depletion of vimentin apparently restored the nuclear shape of the cells, which was devastated by re-expression of vimentin, but not its assembly-defective Y117D mutant. Depletion of plectin, a cytoskeletal linker, partially prevented the perinuclear accumulation of VIFs and concomitantly restored the nuclear shape of the cells. In addition, depletion of vimentin in lung cancer A549 cells largely prevented nuclear dysmorphia during the epithelial-to-mesenchymal transition induced by TGFβ. Moreover, we found that VIF-mediated nuclear dysmorphia led to defects in DNA repair. Together, our results unveil a novel role of VIFs in cancer cell nuclear dysmorphia, which is associated with genome instability.