Metabolic starvation-induced cell swelling drives solid stress in tumors.

Solid stress shapes tumor growth, invasion, and therapeutic response, yet its physical origin and clinical relevance remain unclear. Here, we develop a mechano-electro-osmotic model integrating metabolic gradients, ion transport, and cellular mechanics to explain residual solid stress emergence in tumor spheroids, common models of solid tumors. We show that solid stress arises predominantly from osmotic cell swelling driven by metabolic deprivation and ion accumulation, rather than proliferation. This mechanism generates a characteristic stress architecture: isotropic compression in the hypoxic core balanced by peripheral tangential tension, causing pronounced cell and nuclear deformation. The resulting nuclear strain provides a mechanical basis for DNA damage and genomic instability implicated in disease progression and treatment resistance. We validate these predictions in breast cancer using MDA-MB-231 spheroids and patient-derived ductal carcinoma in situ lesions, and corroborate them across published spheroid models and in vivo and ex vivo tumors spanning additional cancer types. Our findings link tumor metabolism to clinically relevant mechanical stresses, suggesting opportunities to target osmotic and metabolic pathways to mitigate solid stress and improve therapeutic outcomes.