Project description:We have identified a single miRNA, miR-181a, that can modulate TGF-β signaling to induce and maintain EMT, and effect further downstream events of tumour cell survival, altered response to chemotherapy, migration, invasion and dissemination in vivo. Our present study provides an understanding of how enhanced expression of miR-181a can confer malignant and invasive traits through the modulation of a canonical signaling pathway and a consequent maintenance of a mesenchymal state. Furthermore, inhibition of miR-181a led to a reversion of EMT and subsequent events through decreased TGF-β signaling. Our data confirmed Smad7 as a functional target through which TGF-β-mediated EMT occurs; re-expression of Smad7 lacking its 3'UTR was able to rescue miR-181a-mediated phenotypes, deeming Smad7 as a critical mediator of miR-181a-induced EMT. Other recent studies support the crucial role(s) that miRNAs play in mediating EMT and consequent aggressive disease traits. For example, the miR-106b-25 cluster has also been shown to target Smad7 and mediate TGF-β-induced EMT downstream to Six1 in breast cancer34. miR-9 directly targets E-cadherin and inhibition of miR-9 had led to an inhibition of metastasis35. Conversely, the miR-200 and -205 family was shown to target transcriptional repressors of E-cadherin, ZEB1 and SIP1, and re-expression of these miRNAs led to a mesenchymal-to-epithelial transition and prevented TGF-β -induced EMT36. A2780 ovarian cancer cell lines stably expressing either pBABE (control vector), p181a#1( clone 1 expressing miR-181a) or p181a#2( clone 2 expressing miR-181a)
Project description:Genomic instability predisposes cells to malignant transformation, however the molecular mechanisms that allow for the propagation of cells with a high-degree of genomic instability remains unclear. Here we report that miR-181a is able to transform fallopian tube secretory epithelial cells- the precursor cell type for the majority of high-grade serous ovarian cancers- through the inhibition of RB1 and simultaneously drives a cell protective inhibition of the stimulator-of-interferon-genes (STING) in order to maintain a microenvironment conducive to the propagation of cells with a high-degree of genomic instability. We found that miR-181a inhibition of RB1 leads to profound nuclear defects, genomic instability, and nuclear rupture resulting in a persistence of genomic material in the cytoplasm. While normally, this persistence of genomic material in the cytoplasm induces interferon response through STING to drive cell death, miR-181a directly downregulates STING and prevents apoptosis. The most common mechanism by which oncogenic miRNAs promote tumorigenesis is through the direct inhibition of tumor suppressor genes, however our studies highlight a new mechanism of oncomiR transformation through the combination of tumor suppressor gene inhibition and abrogation of immune surveillance that initiates and propagates tumor cell survival. Importantly, we found that miR-181a induction in ovarian patient tumors is tightly associated with decreased IFNg response and downregulation of lymphocyte infiltration amd leukocyte fraction. To date, DNA oncoviruses are the only known inhibitors of STING that allow for cellular transformation thus, our findings are the first to identify a genetic factor, miR-181a, that can downregulate STING expression, suppress activation of the immunosurveillance machinery, and impair signaling in cancer cells creating a survival advantage. Our studies support the notion that the induction of STING-mediated signaling in cancer cells could lead directly to cancer cell death however these effects are abrogated by miR-181a. Given the recent interest in the development of STING agonists as a strategy to harness the immune system to treat cancer, this study introduces novel patient selective biomarker as well as potent therapeutic target for development of the most effective combination treatments.
Project description:Genomic instability predisposes cells to malignant transformation, however the molecular mechanisms that allow for the propagation of cells with a high-degree of genomic instability remains unclear. Here we report that miR-181a is able to transform fallopian tube secretory epithelial cells- the precursor cell type for the majority of high-grade serous ovarian cancers- through the inhibition of RB1 and simultaneously drives a cell protective inhibition of the stimulator-of-interferon-genes (STING) in order to maintain a microenvironment conducive to the propagation of cells with a high-degree of genomic instability. We found that miR-181a inhibition of RB1 leads to profound nuclear defects, genomic instability, and nuclear rupture resulting in a persistence of genomic material in the cytoplasm. While normally, this persistence of genomic material in the cytoplasm induces interferon response through STING to drive cell death, miR-181a directly downregulates STING and prevents apoptosis. The most common mechanism by which oncogenic miRNAs promote tumorigenesis is through the direct inhibition of tumor suppressor genes, however our studies highlight a new mechanism of oncomiR transformation through the combination of tumor suppressor gene inhibition and abrogation of immune surveillance that initiates and propagates tumor cell survival. Importantly, we found that miR-181a induction in ovarian patient tumors is tightly associated with decreased IFNg response and downregulation of lymphocyte infiltration amd leukocyte fraction. To date, DNA oncoviruses are the only known inhibitors of STING that allow for cellular transformation thus, our findings are the first to identify a genetic factor, miR-181a, that can downregulate STING expression, suppress activation of the immunosurveillance machinery, and impair signaling in cancer cells creating a survival advantage. Our studies support the notion that the induction of STING-mediated signaling in cancer cells could lead directly to cancer cell death however these effects are abrogated by miR-181a. Given the recent interest in the development of STING agonists as a strategy to harness the immune system to treat cancer, this study introduces novel patient selective biomarker as well as potent therapeutic target for development of the most effective combination treatments. Infinium CytoSNP-850K v1.2 BeadChip (Illumina) was performed to assess genomic variation