Therapeutic Potential of microRNA
10:25-10:30 Chairperson's Opening Remarks
10:30-11:00 Therapeutic Gene Silencing Using RNA Interference
Bulent Ozpolat, M.D., Ph.D., Assistant Professor, Experimental Therapeutics, University of Texas MD Anderson Cancer Center
11:00-11:30 Manipulating the microRNA Loading Process to Design Better Small RNA Therapeutics
Mark A. Kay, M.D., Ph.D., Dennis Farrey Family Professor, Pediatrics and Genetics; Vice Chair for Basic Research, Pediatrics, Stanford University
11:30-12:00 pm Combinatorial miRNA Therapeutics for the Prevention and Treatment of Lung Cancer
Andrea L. Kasinski, Ph.D., Postdoctoral Fellow, Frank Slack's Lab, Molecular, Cellular and Developmental Biology, Yale University
Using a KrasG12D/+;p53R172H/+ mouse model of aggressive lung cancer, we show that miR-34 can prevent tumors from forming. Untreated animals have high-grade adenocarcinomas leading to macrophage infiltration and death, while miR-34 treated mice have limited-to-no tumorigenesis. We also show a synergistic effect between let-7 and miR-34 for the treatment of lung cancer in the same model. miRNAs in these models are delivered intratracheally via viral particles or more clinically using a lipid-based systemic agent.
12:00-12:30 Activation of miR-31 Function in Already-Established Metastases Elicits Metastatic Regression
Scott J. Valastyan, Ph.D., Research Fellow, Cell Biology, Harvard Medical School
Distant metastases, rather than the primary tumors from which these lesions arise, are responsible for >90% of carcinoma-associated mortality. Many patients already harbor disseminated tumor cells in their bloodstream, bone marrow and distant organs when they initially present with cancer. Hence, truly effective anti-metastatic therapeutics must impair the proliferation and survival of already-established metastases. Here, we assess the therapeutic potential of acutely expressing the microRNA miR-31 in already-formed breast cancer metastases. Activation of miR-31 in established metastases elicits metastatic regression and prolongs survival. Remarkably, even brief induction of miR-31 in macroscopic pulmonary metastases diminishes metastatic burden. In contrast, acute miR-31 expression fails to affect primary mammary tumor growth. miR-31 triggers metastatic regression in the lungs by eliciting cell-cycle arrest and apoptosis; these responses occur specifically in metastases and can be explained by miR-31-mediated suppression of integrina5, radixin, and RhoA. Indeed, concomitant re-expression of these three proteins renders already-seeded pulmonary metastases refractory to miR-31-conferred regression. Upon miR-31 activation, Akt-dependent signaling is attenuated and the pro-apoptotic molecule Bim is induced; these effects occur in a metastasis-specific manner in pulmonary lesions and are abrogated by concurrent re-expression of integrina5, radixin, and RhoA. Collectively, these findings raise the possibility that intervention strategies centered upon restoring miR-31 function may prove clinically useful for combating metastatic disease.
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Role of microRNA in Cancer Mechanism
10:25-10:30 Chairperson's Opening Remarks
10:30-11:00 Talk Title to be Announced
Philip N. Tsichlis, M.D., Jane F. Desforges Professor of Hematology and Oncology; Executive Director, Medical Oncology Research Institute, Tufts Medical Center
11:00-11:30 Impact of Non-Coding miRNAs in Chemoresistance, EMT and Cancer Stem Cells
Jingfang Ju, Ph.D., Professor and Co-Director, Translational Research Laboratory, Pathology, State University of New York at Stony Brook
Our laboratory first discovered that a number of miRNAs were regulated by tumor suppressor p53. Such regulatory mechanism was important in regulating cell proliferation and cell cycle control. To investigate the impact of miRNA in chemoresistance to fluoropyrimidines and antifolates, we discovered that miR-215 suppresses the expression of both thymidylate synthase and dihydrofolate reductase. In addition, the expression of miR-215 was directly regulated by p53. The expression of miR-215 was significantly associated with colorectal cancer patient survival. miR-140 modulates chemosensitivity by suppressing HDAC4 expression, and the levels of miR-140 and miR-215 were elevated in colon cancer stem cells. Our recent studies have shown that miR-194 was directly involved in epithelial-to-mesenchymal (EMT) transition, a critical event for tumor progression and metastasis. The expression of Bmi-1 protein was suppressed by miR-194 directly at the 3'-UTR region of Bmi-1 mRNA. Given the significant role of miRNAs in many aspects of tumor development such as proliferation, cell cycle control, invasion, EMT and maintained tumor stem cell phenotype, we remain hopeful that miRNA based therapeutics, diagnosis and prognosis may emerge in the near future to benefit patients.
11:30-12:00 pm microRNAs and Tumor Angiogenesis
Andrei Thomas-Tikhonenko, Ph.D., Chief, Division of Cancer Pathobiology, The Children's Hospital of Philadelphia
Thrombospondin-1 is an inhibitor of angiogenesis encoded by the THBS1 gene. THBS1 promoter is activated by p53, and its RNA is downregulated by Myc via the miR-17-92 cluster. Additionally, it responds to TGFbeta signaling, which is also inhibited by miR-17-92. Yet in advanced colorectal cancers, THBS1 expression is sustained despite frequent loss of p53, overexpression of miR-17-92, and loss of TGFbeta signaling. We discovered that this is because the loss of p53 also brings down miR-194 levels, which is the key microRNA limiting THBS1 expression. Moreover, stable overexpression of miR-194 in murine colon carcinomas yields increased microvascular densities and vessel sizes, attesting to its pro-angiogenic properties.
12:00-12:30 miRNAs in the Oncogene and Tumor Suppressor Network
Lin He, Ph.D., Assistant Professor, Cell and Developmental Biology, University of California Berkeley
Malignant transformation represents the endpoint of successive genetic lesions that confer uncontrolled proliferation and survival, unlimited replicative potential, and invasive growth. Emerging evidence has suggested that ncRNAs, particularly microRNAs (miRNAs), are essential regulators for gene expression in diverse developmental and physiological processes. We have identified several novel miRNA components in the oncogene and the tumor suppressor pathways. These findings are among the first to include miRNAs into the complex molecular network that impact tumorigenesis. Currently, our major effort is to elucidate the functions of miRNAs in the oncogene and tumor suppressor network, which impact diverse biological processes including tumorigenesis and stem cell biology. In particular, we would like to understand how the unique gene structures and functions of miRNAs contribute to their gene regulatory roles in the context of tumorigenesis and stem cell biology, using both mouse genetic models and cell culture studies.
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microRNA as Targets in Therapeutic Development
2:00-2:05 Chairperson's Opening RemarksAimee Jackson, Ph.D., Consultant, Ingenuity Systems
2:05-2:35 miRNAs as Targets for Overcoming Therapeutic Resistance
Fazlul H. Sarkar, Ph.D., Professor of Pathology, Barbara Ann Karmanos Cancer Institute, Wayne State University School of Medicine
Emerging evidence clearly suggests the important roles of microRNAs (miRNAs) in the regulation of genes that are critical for cancer cells but most importantly for those cancer cells that are highly resistant to conventional therapeutics. Since therapeutic resistance is the cause of treatment failure, novel approaches must be discovered for overcoming such resistance in order to improve the overall survival of patients diagnosed with cancer. This presentation will focus on the mechanistic role of miRNAs in therapeutic resistance and will also provide examples of novel avenues for targeting miRNAs in overcoming therapeutic resistance of pancreas, prostate, breast and lung cancer cells.
2:35-3:05 microRNA Binding Site Disruption in Cancer
Joanne Weidhaas, M.D., Ph.D., Assistant Professor, Therapeutic Radiology, Yale University School of Medicine
The importance of variants in microRNA binding sites in the 3' untranslation region of mRNAs as biomarkers of disease risk has been indisputably shown over the last 5 years. However, new insight into the potential of these variants to act as biomarkers of tumor biology as well as to act as potential future targets for treatment is a novel area that is quickly evolving. These topics will be discussed.
3:05-3:35 microRNAs as Therapeutic Targets in Cardiovascular Disease
Eva van Rooij, Ph.D., Senior Director of Biology, Miragen Therapeutics
Chronic and acute stress to the heart results in a pathological remodeling response accompanied by hypertrophy, fibrosis, myocyte apoptosis and eventual death from pump failure and arrhythmias. We have identified signature expression patterns of microRNAs associated with different forms of heart disease. Gain- and loss-of-function studies have revealed profound and unexpected functions for these microRNAs in numerous facets of cardiac biology, providing glimpses of new regulatory mechanisms and potential therapeutic targets for heart disease. Disease-inducing cardiac microRNAs can be persistently regulated in vivo through systemic delivery of anti-miRs. The therapeutic opportunities for manipulating microRNA biology in the setting of heart disease will be discussed.
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Role of microRNA in Cancer Mechanism (continued)
2:00-2:05 Chairperson's Opening Remarks
2:05-2:35 Multiple P63/P73-Regulated microRNA Pathways Control Essential Steps in Tumor Progression
Benjamin Ory, Ph.D., Associate Professor, Physiopathology of Bone Resorption, Nantes Medical School, INSERM UMR957, France
A central challenge in human cancer therapy is the identification of pathways that control tumor cell survival and chemosensitivity in the absence of functional p53. Through comprehensive profiling of p63-regulated microRNAs (miRs) we identified multiple miR-dependent pathways important for tumor progression; for instance, we identified a new and physiologically important microRNA-dependent network that maintains p63/p73 homeostasis and controls p53-independent survival and chemosensitivity in squamous cell carcinoma. This network involves a subset of miRs that target p73 for inhibition, including miR-193a-5p, a direct endogenous transcriptional target repressed by p63 and activated by pro-apoptotic p73 isoforms. Consequently, chemotherapy treatment causes p63/p73-dependent induction of this miR, thereby limiting chemosensitivity due to miR-mediated feedback control of p73. We have shown that interrupting this feedback by inhibiting miR-193a suppresses tumor cell viability and induces dramatic chemosensitivity both in vitro and in vivo. Expression profiling also allowed us to identify p63-regulated miRs (including a conserved miR cluster) potentially targeting the TGFβ pathway. These miRs repress TGFβRII and Smad4 principally and thereby may interfere with metastasis dissemination.
2:35-3:05 A Novel Oncogenic Role for the miRNA-506-514 Cluster in Initiating Melanocyte Transformation and Promoting Melanoma Growth
Katie Streicher, Ph.D., Scientist II, Translational Science, MedImmune
There is significant need for new therapeutic targets and diagnostic/prognostic biomarkers to improve outcomes in patients with melanoma. Comparison of skin punches from melanoma patients and healthy donors identified a cluster of 14 miRNAs consistently over-expressed 30-60 fold in nearly all melanomas tested. Functional analysis revealed a role for this cluster in regulating cell growth, apoptosis, invasion, and soft agar colony formation, as well as a role in melanocyte transformation. Our results provide insight into the functional role of an oncogenic miRNA cluster in melanoma, which may identify new treatment or stratification strategies for patients with this disease.
3:05-3:35 miRNAs as Modulators of Metastatic Behavior
Eva Hernando, Ph.D., Assistant Professor, Pathology, New York University School of Medicine
Early-stage, localized melanoma is well treatable by surgical resection yielding 5-year survival rates of 98%. Patients with advanced melanoma, however, have progressively worse 5-year survival rates of 62% and 16% in those with regional lymph node involvement and distal metastasis, respectively. Identifying functionally relevant molecular events that occur early in melanoma development may inform clinical decision-making and uncover novel therapeutic targets. We found that microRNA alterations that confer increased metastatic potential can be captured at early stages of melanoma development. Our study supports that molecular defects occuring during melanomagenesis simultaneously impact the progression from a treatable primary tumor to an invasive and ultimately metastatic disease.
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4:00-4:30 Discovery of Novel APP and BACE-specific microRNAs Important for Alzheimer's Disease
Debomoy K. Lahiri, Ph.D., Professor of Neuroscience, Departments of Psychiatry and Medical and Molecular Genetics; Member, Stark Neurosciences Research Institute, Indiana University School of Medicine Institute of Psychiatric Research
Aberrations in Alzheimer's disease are believed to result, in part, from the over-production of amyloid-βpeptide (Aβ), a product of Aβ precursor protein (APP). Expression studies suggest that dysregulation of proteins involved in Aβproduction, such as APP and beta-secretase, or BACE1, contribute to excess Aβ deposition. Elucidating how expression of these proteins is regulated will ultimately reveal new drug targets. We study the regulation of gene products by microRNA, an abundant class of small RNAs with inhibitory effects on gene expression. Our results reveal a novel regulatory interaction between two important AD-related genes (APP and BACE1) and specific endogenously-expressed miRNA species. These regulatory interactions may serve as novel therapeutic targets and enable the development of treatment strategies beneficial for AD.
4:30-5:00 Sensing Global microRNA Activity
Brian D. Brown, Ph.D., Assistant Professor, Genetics and Genomic Sciences, Mount Sinai School of Medicine
microRNAs have emerged as important regulators of gene expression. More than 800 different microRNAs are encoded in the human genome, and each cell type and even cell state appears to express a unique battery of microRNAs. One open question about microRNA regulation is how microRNA concentration relates to target suppression. To gain insight into this process, we generated a panel of microRNA sensors, which enabled us to compare a microRNA's abundance to its activity. Our results provide interesting new insights into microRNA function which are particularly relevant for microRNA profiling.
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4:00-4:30 microRNAs and Melanoma
Prasun J. Mishra, Ph.D., Laboratory of Cancer Biology and Genetics, National Cancer Institute, NIH
Melanoma is a genetically complex and often highly aggressive disease, notorious both for its ability to metastasize and for its poor response to currently available therapeutic approaches. The incidence of melanoma has steadily increased over the last 40 years, and continues to rise at a time when the incidence of other cancers is falling, accounting for 75% of all deaths associated with skin cancer. Moreover, melanoma's propensity to metastasize, even many years after removal of the primary tumor, makes this cancer especially deadly. In this study, using an integrated approach, we have identified and characterized genes and microRNAs associated with melanomagenesis.
4:30-5:00 Hypoxia Induces hESC-Enriched microRNAs in Normal and Cancer Cells
Julie Mathieu, Ph.D., Postdoctoral Fellow, Biochemistry, University of Washington
microRNAs are important new actors in stem cell development by regulating differentiation and maintenance of stem cells. We and others have shown that human embryonic stem cells (hESCs) display a specific microRNA signature and that microRNAs are critical for hESC self-renewal and proliferation. hESCs are derived from the low oxygen environment that characterizes the inner cell mass of blastocysts. However, hESCs are able to self-renew in normoxia or hypoxia. We now show that hypoxia is involved specifically in the acquisition of "stemness" since hypoxia alone can revert differentiated hESCs back to a stem cell-like state. Hypoxia-induced de-differentiated cells also mimic hESCs in their morphology, cell surface markers expression, genome-wide mRNA profile, and capacity to form teratomas. In addition, the set of up-regulated miRNAs in hypoxia de-differentiated cells was highly similar to those enriched in undifferentiated hESCs. These data suggest that hypoxia is sufficient to induce human pluripotent stem cells from committed cells. In cancer, we showed that hypoxia can induce the expression hESC markers in cancer cells, correlating with tumor aggressiveness. Cancer cells cultured under hypoxia also expressed a higher level of hESC-enriched miRNAs compared to cancer cells cultured under normoxia. Hypoxia may therefore induce acquisition of stemness both in normal and cancer cells. Several groups have demonstrated that microRNAs can reprogram somatic cells into pluripotent stem cells, underlying their fundamental role in cell fate decision. We are now investigating whether the effect of hypoxia on the acquisition of stem cell properties is mediated by hESC microRNAs.
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