Mechanical crowding induces HDAC6 nuclear export with functional involvement of XPO1 in HeLa cells

During tumor progression, cells within the solid tumor core experience substantial mechanical crowding (solid stress). Although HDAC6 is a key regulator of cell survival and motility, its spatial regulation under physical crowding remains poorly understood. Here, using HeLa cell monolayers as a model, we show that mechanical crowding promotes the redistribution of HDAC6 from the nucleus to the cytoplasm, whereas fluid shear stress induces the opposite response and favors nuclear accumulation. Expanded immunofluorescence analyses across multiple fields, together with nuclear/cytoplasmic fractionation, support this crowding-associated shift in HDAC6 localization. Transcriptomic profiling further revealed broad remodeling under crowded conditions, including suppression of translation- and cytoskeleton-related programs and enrichment of a candidate export-related signature involving XPO1. Biochemical validation confirmed XPO1 protein expression under crowded conditions, and pharmacological inhibition of XPO1 attenuated the crowding-associated redistribution of HDAC6, supporting a functional role for XPO1 activity in this process. In addition, crowding was accompanied by the upregulation of invasion-associated markers, including MMP9 and Vimentin, suggesting the emergence of a pro-invasive transcriptional state. Together, these findings identify HDAC6 nucleo-cytoplasmic redistribution as a mechanically responsive event under crowding and support the involvement of XPO1 in this adaptation.