Browsing by Subject "Liver Neoplasms, Experimental"
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Item Elucidating the Anti-Cancer Mechanism of Low Density Lipoprotein-Mediated Delivery of Docosahexaenoic Acid to Hepatocellular Carcinoma Cells(2015-07-17) Moss, Lacy Reynolds; Brown, Kathlynn C.; Corbin, Ian R.; Minna, John D.; Repa, Joyce J.Hepatocellular carcinoma is a lethal malignancy with few effective therapy options. New selective treatments are urgently needed to destroy hepatocellular carcinoma cells without harming the surrounding normal hepatocytes. Recently, docosahexaenoic acid has been shown to possess promising anticancer properties. The Corbin laboratory has incorporated docosahexaenoic acid into low density lipoprotein nanoparticles (LDL-DHA) as a means to transport these fatty acids to cancer cells. To test LDL-DHA's efficacy, immortalized mouse normal liver (TIB-73) and isogeneic malignant liver (TIB-75) cell lines were compared. Cell viability and co-culture experiments demonstrated that TIB-75 cells were more sensitive to LDL-DHA than TIB-73 cells. LDL-DHA enters into cells through LDL receptor-mediated endocytosis to the lysosomes. LDL-DHA treatment increased dichlorofluorescein fluorescence in TIB-75 cells over TIB-73 cells, and generation of reactive oxygen species by menadione sensitized TIB-73 cells to LDL-DHA. Importantly, TIB-75 cells were rescued from LDL-DHA cytotoxicity when antioxidants specific for removing lipid peroxide species were added indicating that lipid peroxidation was critical for LDL-DHA cytotoxicity. LDL-DHA also caused lysosomal membrane permeability of only the TIB-75 cells. Subsequent studies showed that only the LDL-DHA treated TIB-75 cells lose their mitochondrial membrane potential. Mitochondrial reactive oxygen species were elevated in TIB-75 cells following LDL-DHA treatment, and TIB-73 cells were sensitized to LDL-DHA after decoupling of mitochondrial respiration. LDL-DHA treatment also caused DNA damage selectively in the TIB-75 cells. When the Fenton reaction, an iron-catalyzed reaction that generates hydroxyl radicals and lipid peroxide species, was blocked by iron chelation, TIB-75 showed less LDL-DHA cytotoxicity, lipid peroxidation, and lysosome leaking. Studies conducted in human hepatocellular carcinoma cells (FOCUS, Hep3B, and Huh7) on LDL-DHA cytotoxicity, lysosome permeability, and mitochondrial reactive oxygen species production confirmed the findings seen in TIB-75 cells following LDL-DHA treatment. Furthermore, primary human hepatocytes were not sensitive to LDL-DHA treatment. In conclusion, these studies have shown that LDL-DHA is selectively cytotoxic to hepatocellular carcinoma cells and that iron-catalyzed lipid peroxidation sets off a subcellular chain of events resulting in increased reactive oxygen species, lysosome permeability, mitochondrial dysfunction, DNA damage, and, ultimately, cell death in hepatocellular carcinoma cells.Item The Role of Polyploidy in the Liver and Its Implications for Cancer Therapy(2018-04-13) Zhang, Shuyuan; O'Donnell, Kathryn A.; Zhu, Hao; Brugarolas, James B.; Yu, HongtaoThe description of liver polyploidy dates back to the 1940s, but its functional roles are still largely unknown. Numerous observations and studies have suggested that liver polyploidy may participate in multiple biological processes, including regeneration, stress response, and cancer. However, little evidence has established direct causal links between polyploidy and the observed phenotypes, mainly due to the lack of appropriate tools to specifically manipulate ploidy levels without causing other permanent changes. Specifically, whether polyploidy promotes or inhibits cancer is still under debate. Inspired by a phenomenon we observed in somatically mutated mouse livers, where homozygous Apc deletions were more difficult to obtain due to hepatic polyploidy, we aimed to build inducible tools to manipulate liver ploidy levels in vivo and systematically study the role of polyploidy in liver cancer. By toggling the weaning time and levels of Anln or E2f8 genes to change liver ploidy levels, we found that liver tumorigenesis was inversely correlated with initial polyploidy levels, suggesting a tumor suppressive role for polyploidy. Moreover, the additional alleles in polyploid cells led to a reduced likelihood of loss of heterozygosity (LOH), which largely contributed to the tumor suppressive effect. These results revealed an important function of polyploidy in mammalian livers and also led us to seek related therapeutic strategies for treating liver cancer. Since hepatocyte polyploidization mainly occurs through cytokinesis failure, we hypothesized that inhibiting cytokinesis could be an effective strategy to suppress liver tumorigenesis while preserving normal liver function. Therefore, we inhibited cytokinesis via Anln knockdown in multiple models and found that liver tumor development was significantly suppressed but normal liver function and regeneration capacity were not impaired. These results suggest that cytokinesis inhibition via Anln knockdown is potentially a safe and efficacious strategy for suppressing liver cancer. Overall, we uncovered an important role of polyploidy in the liver and explored its potential applications in liver cancer therapy.