Selective Nucleophagy Activation by Lithium Chloride in a 3D In Vitro Model of Endometrial Carcinoma

Nucleophagy, the selective autophagic degradation of nuclear components, remains poorly characterized in mammalian systems, particularly in cancer. While lithium chloride (LiCl) is known to modulate mitophagy and cellular stress responses, its impact on nuclear architecture has not been ultrastructurally defined. In this study, three-dimensional spheroids of Ishikawa endometrial cancer cells were treated with 10 mM or 50 mM LiCl for up to 96 hours. Cell cycle distribution, BrdU incorporation, and viability were assessed via flow cytometry and immunohistochemistry, while ultrastructural changes were analyzed using transmission electron microscopy (TEM). High-dose LiCl (50 mM) induced marked G1/G0 arrest and reduced S-phase entry, accompanied by a sustained decrease in BrdU-positive cells. Annexin V-FITC/PI staining revealed reduced viability without a corresponding increase in apoptotic or necrotic fractions. TEM analysis showed nuclear envelope elongation, double-membraned vesicles, and cytoplasmic lysis—features consistent with nucleophagy. Preliminary data with 10 mM LiCl demonstrated early nuclear remodeling and autophagic vacuole formation, supporting a time- and dose-dependent induction of nucleophagy in response to lithium exposure. Collectively, these findings provide the first ultrastructural evidence of LiCl-induced nucleophagy in a 3D in vitro endometrial cancer model. Our results indicate that lithium triggers non-apoptotic nuclear degradation alongside mitophagy, expanding its role in autophagy-related stress responses. Nucleophagy may represent a novel mechanism of lithium-mediated modulation in cancer biology.