Polyploid Giant Cancer Cells as a Senescence-Linked State in the Tumor Microenvironment.

Cellular senescence and polyploidy are fundamental stress responses that shape cancer progression and therapeutic outcomes. While senescence initially suppresses tumor growth, senescent cells accumulate in aging and therapy-exposed tissues and actively remodel the tumor microenvironment through the senescence-associated secretory phenotype (SASP) and extracellular matrix (ECM) reorganization. Senescent stromal cells increase collagen deposition and generate disordered matrix architectures, as evidenced by enhanced second harmonic generation (SHG) signal and increased anisotropic variation across in vitro systems, 3D co-culture models, and fibrotic lung tissues. These biochemical and mechanical alterations promote cancer cell plasticity and create conditions permissive for disease progression. Polyploid giant cancer cells (PGCCs) are a rare but highly resilient cancer cell population enriched under genotoxic stress. PGCCs arise through mitotic failure, including mitotic slippage and cytokinesis defects, and can survive chemotherapy and radiation due to their altered cell-cycle regulation. Emerging evidence indicates that senescence-driven microenvironments promote the formation of PGCCs and multinucleated cells, linking ECM remodeling and mechanical stress to polyploidization. Functionally, PGCCs exhibit abnormal cytoskeletal and nuclear mechanics that support migratory persistence and enable survival within hostile tumor environments. In addition, PGCCs can promote the survival of neighboring cancer cells during treatment, suggesting a stromal-like role in establishing therapy-resistant niches. These cells can persist in a dormant state and later generate proliferative progeny, contributing to tumor recurrence and metastasis. Together, these findings support a model in which senescent niches may promote PGCC formation, persistence, and tumor repopulation. Targeting both senescence-associated microenvironments and PGCC-specific survival mechanisms may improve long-term therapeutic outcomes.