Remodeling of cholesterol metabolism in melanoma progression regulates nuclear membrane mechanics.

Metastatic cancer cells migrate through physically restrictive environments where nuclear deformation ruptures the nuclear envelope (NE) resulting in genomic instability. Although structural proteins of the NE are established regulators of nuclear mechanics, how nuclear membrane (NM) lipid composition contributes to its biophysical response to mechanical stress remains poorly understood. Here, we show that melanoma progression is associated with broad transcriptional remodeling of cholesterol homeostasis that is established early in disease progression, with altered expression of cholesterol biosynthesis genes associated with reduced patient survival. Building on our previous identification of the inner NM sterol reductase lamin B receptor (LBR) as a regulator of NE fragility, we find that LBR-dependent cholesterol biosynthesis promotes cholesterol enrichment within the NM and alters its spatial organization during cellular confinement. Quantitative fluorescence and lifetime imaging of biosensors of cholesterol distribution, lipid order, and tension reveals that cholesterol remodeling alters NM lipid organization and results in high NM tension in melanoma cells that is selectively reduced by cholesterol depletion. Cellular confinement generates nuclear blebs where cholesterol becomes preferentially enriched at highly curved, rupture-prone regions of the NM. Together, our results establish cholesterol-dependent NM remodeling as a regulator of nuclear mechanics and link metabolic changes acquired during cancer progression to the biophysical response of the NM to mechanical stress.