Autophagy is essential for survival and function of polyploid giant cancer cells under therapeutic stress.

Polyploid giant cancer cells (PGCCs) are enlarged, multinucleated tumor cells that arise in response to stressors such as chemotherapy and are increasingly recognized as key drivers of recurrence and metastasis in aggressive cancers. Found in triple-negative breast cancer (TNBC) and ovarian cancer (OC), PGCCs can survive cytotoxic therapy in a dormant state and later produce chemoresistant progeny through amitotic budding. Here, we investigated the role of autophagy in paclitaxel (PTX)-induced PGCC survival, nuclear maintenance, and migration. PGCCs generated from MDA-MB-231 and HEY cells were significantly larger, more heterogeneous, and more resistant to PTX than parent cells. Transcriptomic profiling revealed enrichment of metabolic and cytoskeletal pathways, with strong upregulation of autophagy-related genes, including SQSTM1 (P62), LC3, and LAMP1. PGCCs exhibited elevated oxidative stress and marked induction of mitochondrial superoxide dismutase 2 (SOD2). p62 was localized near micronuclei, and prolonged autophagy inhibition with Bafilomycin A1 reduced nuclear size, heterogeneity, and micronuclei number. PGCCs also displayed a dispersed vimentin intermediate filament network that scaffolded autophagic structures; autophagy inhibition impaired migration in PGCC-derived daughter cells. These findings identify autophagy as a critical process sustaining PGCC survival, structural integrity, and motility, and suggest that targeting autophagy may disrupt PGCC-driven recurrence in aggressive cancers.