Lithium-Induced Modulation of Proliferation and Apoptosis in an In Vitro Model of Colorectal Cancer

Cancer involves uncontrolled cell growth, leading to tumor formation, and remains a major cause of mortality worldwide. Colorectal cancer (CRC) arises from abnormal proliferation of colon glandular epithelial cells. We assessed the cytotoxic and molecular effects of lithium carbonate (Li₂CO₃) and lithium chloride (LiCl) in two CRC cell lines (HCT-116 and SW-620) and a non-tumorigenic line (CRL-1790). Viability assays revealed dose-dependent cytotoxicity, with HCT-116 being the most sensitive cell line (IC₅₀: 8.14 mM for Li₂CO₃). Notably, long-term lithium exposure reduced proliferation, lowering colony-forming efficiency (CFE) and a phenotypic shift from holoclones to meroclones and paraclones, indicating diminished self-renewal capacity. Minimal membrane damage was observed (LDH assay), suggesting non-lytic mechanisms consistent with apoptosis. TUNEL and Annexin-V/IP assays confirmed apoptosis in >40% of cells, without caspase-3 cleavage, suggesting a caspase-independent pathway. PARP-1 cleavage occurred only in SW-620 cells. Western blotting exposed cell-specific modulation of GSK-3β: increased inactive form (p-Ser9) in CRC cells and decreased in CRL-1790 cells, implying differential disruption of Wnt/β-catenin signaling. c-Myc levels remained unchanged, suggesting possible post-translational regulatory effects. Overall, these findings indicate that lithium salts selectively reduce CRC cell viability, impair stem-like characteristics, and induced caspase-independent apoptosis. Therefore, we expand the proof of concept of the potential of lithium-based compounds as low-toxicity adjuvant agents in colorectal cancer therapy.