Ultrastructural Nuclear Envelope Remodeling Following Lithium Chloride Exposure in 3D Endometrial Carcinoma Spheroids

Selective remodeling of nuclear components under cellular stress remains insufficiently documented at the ultrastructural level in mammalian cancer models. Lithium chloride (LiCl) is widely used as a pharmacological stressor and modulator of autophagy-related processes; however, its impact on nuclear envelope architecture in three-dimensional (3D) tumor systems has not been systematically characterized. In this study, 3D spheroids derived from Ishikawa endometrial carcinoma cells were exposed to LiCl (10 mM or 50 mM) for up to 96 h. Functional analyses including cell cycle profiling, BrdU incorporation, and viability assessment were combined with transmission electron microscopy to evaluate structural alterations. High-dose LiCl treatment resulted in sustained G₀/G₁ accumulation and suppression of DNA synthesis in the absence of classical apoptotic or necrotic cell death. Ultrastructural examination revealed pronounced nuclear envelope elongation, membrane reorganization, and the presence of double-membraned vesicular structures in close proximity to the nuclear periphery. These changes displayed clear time- and dose-dependent characteristics. Although molecular markers of nucleophagy were not assessed, the observed structural features are morphologically consistent with nucleophagy-like nuclear remodeling. Overall, the 3D spheroid model enabled detailed spatial characterization of stress-associated nuclear membrane dynamics and provides a structural framework for further investigation of nuclear-selective autophagy processes in cancer cells.