Mesenchymal transitions reduce lamin A expression and nuclear stiffness to enhance confined migration in glioblastoma.

The evolution of glioblastoma (GBM) is coupled with a proneural-to-mesenchymal transition (PMT) that exacerbates disease in part through heightened cell invasiveness and spread. PMT follows similar molecular and phenotypic features with epithelial to mesenchymal transitions (EMT) and promotes rapid GBM invasion despite tight physical barriers in the dense brain parenchyma. Recent studies suggest that efficient confined migration is key to navigating these physical constraints; however, the role of PMT in mediating rapid confined migration remain unclear. Using microchannel platforms, AFM, and molecular assays, we explore this question through a biophysical lens to investigate the impact of GBM mesenchymal transformation on cellular mechanics and confined migration. We found that TGF-β1 induced PMT decreased expression and organization of Lamin A, leading to a reduction in nuclear stiffness, especially in U251 cells (1278 Pa → 682.6 Pa). Mesenchymal U251s migrated more quickly through confined microchannels though mesenchymal U87s migrated more slowly. Notably, nuclear stiffening via RO-3306 dramatically reduced confined migration speed in TGF-β1 treated U251 cells. Our study reveals that TGF-β1 induced PMT reduces Lamin A expression and softens the nucleus to support efficient confined migration in a cell-type dependent manner. These findings indicate that PMT alters the biophysical properties of the cell, opening new directions for developing therapeutic strategies for this deadly disease.