Lithium Modulates Autophagy in Esophageal and Colorectal Cancer Cells and Enhances the Efficacy of Therapeutic Agents In Vitro and In Vivo

Abstract

Many epithelial cancers, particularly gastrointestinal tract cancers, remain poor prognosis diseases, due to resistance to cytotoxic therapy and local or metastatic recurrence. We have previously shown that apoptosis incompetent esophageal cancer cells induce autophagy in response to chemotherapeutic agents and this can facilitate their recovery. However, known pharmacological inhibitors of autophagy could not enhance cytotoxicity. In this study, we have examined two well known, clinically approved autophagy inducers, rapamycin and lithium, for their effects on chemosensitivity in apoptosis incompetent cancer cells. Both lithium and rapamycin were shown to induce autophagosomes in esophageal and colorectal cancer cells by western blot analysis of LC3 isoforms, morphology and FACS quantitation of Cyto-ID or mCherry-GFP-LC3. Analysis of autophagic flux indicates inefficient autophagosome processing in lithium treated cells, whereas rapamycin treated cells showed efficient flux. Viability and recovery was assessed by clonogenic assays. When combined with the chemotherapeutic agent 5-fluorouracil, rapamycin was protective. In contrast, lithium showed strong enhancement of non-apoptotic cell death. The combination of lithium with 5-fluorouracil or oxaliplatin was then tested in the syngenic mouse (balb/c) colorectal cancer model—CT26. When either chemotherapeutic agent was combined with lithium a significant reduction in tumor volume was achieved. In addition, survival was dramatically increased in the combination group (p < 0.0001), with > 50% of animals achieving long term cure without re-occurrence (> 1 year tumor free). Thus, combination treatment with lithium can substantially improve the efficacy of chemotherapeutic agents in apoptosis deficient cancer cells. Induction of compromised autophagy may contribute to this cytotoxicity.

GSK-3 Inhibitors: A Double-Edged Sword? – An Update on Tideglusib

“…Similar studies with lithium on colorectal cancer exhibited reduction in cell viability mediated by ROS [56]. Lithium has also been reported to modulate the efficacy of therapeutic agents through autophagy in oesophageal and colorectal cancer [57]. Investigations by Duffy et al demonstrated the therapeutic potential of Lithium which was further substantiated by our study on neuroblastoma IMR32 cells.…”

Prognostic relevance of autophagy markers LC3B and p62 in esophageal adenocarcinomas

“…O'Donovan et al [16] reported that chemoresistant esophageal cancer cell lines induce cytoprotective autophagy upon treatment. A recent follow up study [17] added that pharmacological autophagy inducers rapamycin and lithium had diverging effects when combined with chemotherapeutic agents in esophageal cancer cell lines. Given the different research settings it is difficult to situate our current work in relation to the aforementioned studies.…”

Ultrastructural and Immunofluorescent Analysis of Lithium Effects on Autophagy in Hepatocellular Carcinoma Cells

“…It has been shown that lithium is effective in inhibiting glioma [31], esophageal cancer [32], pancreatic cancer [33], colorectal cancer [34], leukemia and other cancer cells; and several studies suggested the beneficial effects of lithium on cancer cell death and autophagy. O'Donovan et al [36] have demonstrated that lithium-treated colorectal cells showed autophagosomes formation and vesicle accumulation. In addition, other study reported that treatment with 30 mM LiCl increased autophagic flux in colon cancer cells [37].…”