<p>Glutamine plays a vital role in cellular biomass synthesis, serving as a key nutrient. Cancer profoundly impacts cellular size, promoting rapid proliferation and enhanced survival. Understanding the molecular mechanisms that regulate cell size in cancer is essential for designing interventions that can disrupt these processes and inhibit tumor progression. Polyploid giant cancer cells (PGCCs) represent a distinct subpopulation of tumor cells that are implicated in tumor initiation, immortality, invasion, metastasis, and resistance to chemotherapy and radiotherapy. These cells are characterized by their markedly increased size and polyploidy, underscoring the significance of cell size regulation in cancer biology. Although glutamine is known to influence cell growth, its role in regulating cell size remains poorly understood. Wee1, a key cell cycle regulator, controls the timing of mitotic entry, and is known to modulate cell size by preventing premature division. However, the potential link between glutamine, Wee1, and cell size has not been previously explored. In the present study, we investigated the role of glutamine in regulating cellular size. We found that glutamine depletion results in a significant reduction in cell size, along with decreased Wee1 expression at both mRNA and protein levels. Additionally, transient knockdown of Wee1 also led to a reduction in cellular size, reinforcing its role as a regulator of cell size. Moreover, we observed that cytochalasin-B–induced polyploidy was diminished under glutamine-deprived conditions, further affirming the importance of glutamine in maintaining polyploidy and cell size. Overall, our findings clearly indicate that glutamine is a key mediator of cellular size, and that glutamine regulates cell size at least in part through its influence on Wee1. These insights contribute to a better understanding of metabolic control of cell size in cancer and may offer novel therapeutic opportunities.</p>