Proliferation and Tumorigenesis of a Murine Sarcoma Cell Line in the Absence of DICER1

Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
Cancer cell (Impact Factor: 23.52). 06/2012; 21(6):848-55. DOI: 10.1016/j.ccr.2012.04.037
Source: PubMed


MicroRNAs are a class of short ~22 nucleotide RNAs predicted to regulate nearly half of all protein coding genes, including many involved in basal cellular processes and organismal development. Although a global reduction in miRNAs is commonly observed in various human tumors, complete loss has not been documented, suggesting an essential function for miRNAs in tumorigenesis. Here we present the finding that transformed or immortalized Dicer1 null somatic cells can be isolated readily in vitro, maintain the characteristics of DICER1-expressing controls and remain stably proliferative. Furthermore, Dicer1 null cells from a sarcoma cell line, though depleted of miRNAs, are competent for tumor formation. Hence, miRNA levels in cancer may be maintained in vivo by a complex stabilizing selection in the intratumoral environment.

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    • "KP-D cells proliferated more rapidly (Figure 6C) and formed colonies more efficiently (Figures 6D and 6E) and more densely relative to KP cells (Figure 6F). These findings are consistent with impaired tumor suppressor function of dicer in KP-D versus KP cells and mirror the more aggressive pathology observed for KP-D versus KP tumors (Kumar et al., 2009; Ravi et al., 2012; Mito et al., 2013). "
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    ABSTRACT: Genetic defects in the microRNA (miRNA) generating enzyme, dicer, are increasingly linked to disease. Loss of miRNA in dicer deficiency is thought to be due to loss of miRNA-generating activity. Here, we demonstrate a catabolic mechanism driving miRNA depletion in dicer deficiency. We developed a Dicer-antagonist assay revealing a pre-miRNA degrading enzyme that competes with pre-miRNA processing. We purified this pre-miRNA degrading activity using an unbiased chromatographic procedure and identified the ribonuclease complex Translin/Trax (TN/TX). In wild-type dicer backgrounds, pre-miRNA processing was dominant. However, in dicer-deficient contexts, TN/TX broadly suppressed miRNA. These findings indicate that miRNA depletion in dicer deficiency is due to the combined loss of miRNA-generating activity and catabolic function of TN/TX. Importantly, inhibition of TN/TX mitigated loss of both miRNA and tumor suppression with dicer haploinsufficiency. These studies reveal a potentially druggable target for restoring miRNA function in cancers and emerging dicer deficiencies. Copyright © 2014 The Authors. Published by Elsevier Inc. All rights reserved.
    Cell Reports 11/2014; 9(4):1471-1481. DOI:10.1016/j.celrep.2014.10.021 · 8.36 Impact Factor
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    • "Further evidence for a role for miRNA in suppressing cancer has been obtained in mice, wherein haplo-insufficiency for Dicer reduces survival in a model of Kras-driven lung cancers [8], and a reduction in Dicer gene dosage induces high-grade serous carcinomas within the fallopian tubes of PTEN-conditional mice [9]. Thus, while total loss of Dicer function appears deleterious to normal cell growth, Dicer activity is not absolutely required for the growth of transformed cells, and perturbation of Dicer and miRNA maturation may facilitate tumorigenesis in some settings [10]. "
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    ABSTRACT: Dicer is required for the maturation of microRNA, and loss of Dicer and miRNA processing has been found to alter numerous biological events during embryogenesis, including the development of mammalian skin and hair. We have previously examined the role of miRNA biogenesis in mouse embryonic fibroblasts and found that deletion of Dicer induces cell senescence regulated, in part, by the p53 tumor suppressor. Although Dicer and miRNA molecules are thought to have either oncogenic or tumor suppressing roles in various types of cancer, a role for Dicer and miRNAs in skin carcinogenesis has not been established. Here we show that perinatal ablation of Dicer in the skin of mice leads to loss of fur in adult mice, increased epidermal cell proliferation and apoptosis, and the accumulation of widespread DNA damage in epidermal cells. Co-ablation of Dicer and p53 did not alter the timing or extent of fur loss, but greatly reduced survival of Dicer-skin ablated mice, as these mice developed multiple and highly aggressive skin carcinomas. Our results describe a new mouse model for spontaneous basal and squamous cell tumorigenesis. Furthermore, our findings reveal that loss of Dicer in the epidermis induces extensive DNA damage, activation of the DNA damage response and p53-dependent apoptosis, and that Dicer and p53 cooperate to suppress mammalian skin carcinogenesis.
    PLoS ONE 06/2014; 9(6):e100920. DOI:10.1371/journal.pone.0100920 · 3.23 Impact Factor
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    • "Dicer dependent cell death during Kras driven ADM suggests that pancreatic cells exhibit similar negative selection against Dicer loss similar to that seen in a number of tumor models, [13], [14], [15], [48], [50]. In line with this observation, 2 of 3 cell lines derived from PDA in Kras; DicerHomo mice maintained at least one intact Dicer allele. "
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    ABSTRACT: miRNA levels are altered in pancreatic ductal adenocarcinoma (PDA), the most common and lethal pancreatic malignancy, and intact miRNA processing is essential for lineage specification during pancreatic development. However, the role of miRNA processing in PDA has not been explored. Here we study the role of miRNA biogenesis in PDA development by deleting the miRNA processing enzyme Dicer in a PDA mouse model driven by oncogenic Kras. We find that loss of Dicer accelerates Kras driven acinar dedifferentiation and acinar to ductal metaplasia (ADM), a process that has been shown to precede and promote the specification of PDA precursors. However, unconstrained ADM also displays high levels of apoptosis. Dicer loss does not accelerate development of Kras driven PDA precursors or PDA, but surprisingly, we observe that mouse PDA can develop without Dicer, although at the expense of proliferative capacity. Our data suggest that intact miRNA processing is involved in both constraining pro-tumorigenic changes in pancreatic differentiation as well as maintaining viability during PDA initiation.
    PLoS ONE 05/2014; 9(5):e95486. DOI:10.1371/journal.pone.0095486 · 3.23 Impact Factor
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