| 1. |
- Harada, Masako
(author)
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MiRNAs in cancer
- 2012
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Doctoral thesis (other academic/artistic)abstract
- There are many layers of complexity involving the processes through which somatic cells transform into malignant cancers. Historically, cancer was considered to be a disease primarily caused by gene mutations, however it is now well established that the dysregulated expression of the genes leading to the tumorigenic phenotype involves not only mutations but also epigenetic changes. To understand the process of malignant transformation, it is thus important to determine the specific genes targeted by both types of changes. The studies in this thesis have focused on miRNA expression and its dysregulation in various malignancies and the subsequent role of such dysregulation in tumor pathogenesis. The work includes an analysis of the functional consequences of miRNA alterations in three distinct malignancies, (1) chronic lymphocytic leukemia (CLL), (2) Squamous cell carcinoma (SCC) and (3) Basal cell carcinoma (BCC). Furthermore, acute lymphoblastic leukemia (ALL) was used as a model to describe the role of miRNAs in anticancer treatment. Moreover, we analyzed the effect of the anticancer drug dexamethasone on miRNA expressions and the impact of manipulation of miRNA levels on drug efficacy. In the CLL study, we demonstrated that the frequently deleted DLEU2 gene functions as a regulatory host gene for two miRNAs, miR-15a and miR16-1, which negatively regulate the cell cycle by direct targeting G1 cyclins D1 and E1 at the post-transcriptional level, and which, when expressed at high levels in cell line models, lead to the inhibition of colony formation ability. In addition, we demonstrated that the oncoprotein Myc negatively regulates DLEU2 transcription by targeting the DLEU2 promoter. These results suggest that the loss of DLEU2 may be an important pathogenic factor in CLL development. Our studies on two non-melanoma-skin cancers, SCC and BCC, identified the preferential loss of expression of a skin-specific miRNA, miR-203, in these tumors. Our results further indicate a function of miR-203 in cell cycle regulation, migration and invasion, through the post-transcriptional targeting of the oncogenes c-JUN and c-MYC, and ultimately leading to an inappropriate inactivation of Hedgehog pathway. Finally, in the ALL study we demonstrated dexamethasone mediated global down-regulation of miRNAs, in particular the rapid downregulation of MIR17HG which occurred following direct binding of the glucocorticoid receptor protein to the MIR17HG promoter. The subsequent repression of miR-17 expression aids in dexamethasone cytotoxicity of ALL cells, possibly through de-repression of miR-17 mediated targeting of the anti-apoptotic protein Bim. Analysis of primary B-ALL tumor samples also demonstrated that the cytotoxic efficacy of dexamethasone is associated with its ability to regulate miR-17 levels. Collectively, these results provide new evidence, not only on the function and importance of microRNAs in tumor pathogenesis, but also suggest the possibility of miRNA targeting to improve the efficacy of existing therapies.
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| 2. |
- Lohcharoenkal, Warangkana, et al.
(author)
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MicroRNA-203 Inversely Correlates with Differentiation Grade, Targets c-MYC, and Functions as a Tumor Suppressor in cSCC.
- 2016
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In: Journal of Investigative Dermatology. - : Elsevier BV. - 0022-202X .- 1523-1747. ; 136:12, s. 2485-2494
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Journal article (peer-reviewed)abstract
- Cutaneous squamous cell carcinoma (cSCC) is the second most common cancer and a leading cause of cancer mortality among solid organ transplant recipients. MicroRNAs (miR) are short RNAs that regulate gene expression and cellular functions. Here, we show a negative correlation between miR-203 expression and the differentiation grade of cSCC. Functionally, miR-203 suppressed cell proliferation, cell motility, and the angiogenesis-inducing capacity of cSCC cells in vitro and reduced xenograft tumor volume and angiogenesis in vivo. Transcriptomic analysis of cSCC cells with ectopic overexpression of miR-203 showed dramatic changes in gene networks related to cell cycle and proliferation. Transcription factor enrichment analysis identified c-MYC as a hub of miR-203-induced transcriptomic changes in squamous cell carcinoma. We identified c-MYC as a direct target of miR-203. Overexpression of c-MYC in rescue experiments reversed miR-203-induced growth arrest in cSCC, which highlights the importance of c-MYC within the miR-203-regulated gene network. Together, miR-203 acts as a tumor suppressor in cSCC, and its low expression can be a marker for poorly differentiated tumors. Restoration of miR-203 expression may provide a therapeutic benefit, particularly in poorly differentiated cSCC.
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| 3. |
- Xu, Ning, et al.
(author)
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MicroRNA-125b down-regulates matrix metallopeptidase 13 and inhibits cutaneous squamous cell carcinoma cell proliferation, migration, and invasion.
- 2012
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In: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 287:35, s. 29899-908
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Journal article (peer-reviewed)abstract
- Cutaneous squamous cell carcinoma (cSCC) is the second most common human cancer. Although dysregulation of microRNAs (miRNAs) is known to be involved in a variety of cancers, the role of miRNAs in cSCC is unclear. In this study, we aimed to identify tumor suppressive and oncogenic miRNAs involved in the pathogenesis of cSCC. MiRNA expression profiles in healthy skins (n = 4) and cSCCs (n = 4) were analyzed using MicroRNA Low Density Array. MiR-125b expression was analyzed by quantitative real-time PCR and in situ hybridization in skin biopsies from 40 healthy donors, 13 actinic keratosis, and 74 cSCC patients. The effect of miR-125b was analyzed in wound closure, colony formation, migration, and invasion assays in two cSCC cell lines, UT-SCC-7 and A431. The genes regulated by miR-125b in cSCC were identified by microarray analysis and its direct target was validated by luciferase reporter assay. Comparing cSCC with healthy skin, we identified four up-regulated miRNAs (miR-31, miR-135b, miR-21, and miR-223) and 54 down-regulated miRNAs, including miR-125b, whose function was further examined. We found that miR-125b suppressed proliferation, colony formation, migratory, and invasive capacity of cSCC cells. Matrix metallopeptidase 13 (MMP13) was identified as a direct target suppressed by miR-125b, and there was an inverse relationship between the expression of miR-125b and MMP13 in cSCC. Knockdown of MMP13 expression phenocopied the effects of miR-125b overexpression. These findings provide a novel molecular mechanism by which MMP13 is up-regulated in cSCCs and indicate that miR-125b plays a tumor suppressive role in cSCC.
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