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The Biological Functions of miR-122 and its Therapeutic Application in Liver Cancer

Hsu, Shu-hao
http://rave.ohiolink.edu/etdc/view?acc_num=osu1338316658

Abstract Details

2012, Doctor of Philosophy, Ohio State University, Molecular, Cellular and Developmental Biology.
miR-122, the most abundant liver-specific microRNA (miRNA), is involved in many different biological functions, including cholesterol metabolism, hepatitis C virus replication, and hepatocarcinogenesis. Previous studies have shown that downregulation of miR-122 in hepatocellular carcinoma (HCC) correlates with metastasis and poor prognosis. Among the deregulated miRNAs in HCC, miR-122 is drastically reduced in HCC. Based on these observations, our hypothesis is that miR-122 is a liver-specific tumor suppressor and its loss may promote hepatocarcinogenesis. To test this hypothesis, we generated germ-line (KO) and liver-specific (LKO) miR-122 knockout mice. Both KO and LKO mice exhibited hepatic microsteatosis and hepatic inflammation at early adult stage. Lipid analysis showed accumulated hepatic triglyceride, which correlated with increased de novo triglyceride synthesis and reduced triglyceride secretion. By 6 month both KO and LKO mice develop hepatic steatosis, inflammation, and fibrosis. After twelve months, these mice produce spontaneous liver tumors resembling HCC. The HCC incidences were ~30% and ~50% in LKO and KO mice, respectively. Microarray and realtime RT-PCR analysis attributed these pathological phenotypes to dysregulated expression of signaling pathways involved in triglyceride synthesis, cytokine expression, and oncogenesis. Among the deregulated genes, Agpat1, Cidec and Mapre1 were identified for the first time as the direct targets of miR-122. Exploration of the mechanism leading to hepatic inflammation in KO and LKO mice led to the identification of CD11bhighGr-1+ subtype of inflammatory cells increased in the liver of KO mice. These cells were determined as the major source of high levels of IL-6 and TNF-α that accumulated in the livers of KO and LKO mice. Ccl2, a reported myeloid chemo-attractant, was induced in hepatocytes of KO and LKO mice and was inversely regulated by miR-122 in vitro. To establish further the tumor suppressor role of miR-122, we tested the feasibility of the therapeutic delivery of miR-122 to the liver and tumor cells by lipid-based nanoparticles, which is recognized as a safe delivery method due to its biocompatibility. We developed a novel LNP, designated LNP-DP1, consisting of a conditionally ionizable cationic lipid, 2-dioleyloxy-N,N-dimethyl-3-aminopropane (DODMA), egg PC, cholesterol (Chol) and Chol-polyethylene glycol (Chol-PEG). Ectopic expression of miR-122 in HCC cell lines by LNP-DP1 reduced expression of miR-122 targets, such as Adam10, by >95%. The biodistribution analysis revealed that hepatocytes and tumor epithelial cells preferentially took up systemic circulated LNP-DP1 conjugated fluorescence labeled siRNA. Serum profile of treated mice showed that LNP-DP1 did not induce significant liver or kidney damage in mice. Several target genes of miR-122 were downregulated after systemic delivery of LNP-DP1 conjugated miR-122. This result suggested that miR-122 was successfully released from LNP-DP1 and was functional in hepatocytes and tumor cells. Furthermore, intratumoral injection of LNP-DP1 conjugated miR-122 into HCC xenograft developed in nude mice resulted in suppression of tumor growth within 30 days of miR-122 delivery. In conclusion, these findings revealed critical functions for miR-122 in liver metabolism, hepatic immune response, and in hepatocarcinogenesis. The application of miR-122 delivery by LNP-DP1 in animal HCC model suggested potential utility of miR-122 therapy for selected HCC patients negative for HCV.
Samson Jacob (Advisor)
Kalpana Ghoshal (Advisor)
Thomas Schmittgen (Committee Member)
Robert Lee (Committee Member)
David Symer (Committee Member)
Biology; Biomedical Engineering; Biomedical Research; Oncology
miR-122; cationic lipid based nanoparticle; liver cancer; knockout mice

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Citations

  • Hsu, S.-H. (2012). The Biological Functions of miR-122 and its Therapeutic Application in Liver Cancer [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1338316658

    APA Style (7th edition)

  • Hsu, Shu-hao. The Biological Functions of miR-122 and its Therapeutic Application in Liver Cancer. 2012. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1338316658.

    MLA Style (8th edition)

  • Hsu, Shu-hao. "The Biological Functions of miR-122 and its Therapeutic Application in Liver Cancer." Doctoral dissertation, Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1338316658

    Chicago Manual of Style (17th edition)

osu1338316658
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© 2012, all rights reserved.
This open access ETD is published by The Ohio State University and OhioLINK.