Project description:We determined the effect of p53 activation on de novo protein synthesis using quantitative proteomics of newly synthesized proteins (pulsed stable isotope labeling with amino acids in cell culture, pSILAC) in combination with mRNA and non-coding RNA expression analyses by next generation sequencing (RNA-, miR-Seq) in the colorectal cancer (CRC) cell line SW480. Furthermore, genome-wide DNA binding of p53 was analyzed by chromatin-immunoprecipitation (ChIP-Seq). Thereby, we identified differentially regulated mRNAs (1258 up, 415 down), miRNAs (111 up, 95 down), lncRNAs (270 up, 123 down) and proteins (542 up, 569 down). Changes in mRNA and protein expression levels showed a positive correlation (r = 0.50, p < 0.0001). More transcriptionally induced genes displayed occupied p53 binding sites (4.3% mRNAs, 7.2% miRNAs, 6.3% lncRNAs, 5.9% proteins) than repressed genes (2.4% mRNAs, 3.2% miRNAs, 0.8% lncRNAs, 1.9% proteins), suggesting indirect mechanisms of repression. Around 50% of the downregulated proteins displayed seed-matching sequences of p53-induced miRNAs in the corresponding 3â??-UTRs. Moreover, proteins repressed by p53 significantly overlapped with those previously shown to be repressed by miR-34a. We confirmed upregulation of the novel direct p53 target genes LINC01021, MDFI, ST14 and miR-486 and showed that ectopic LINC01021 expression inhibited proliferation in SW480 cells. Furthermore, HMGB1, KLF12 and CIT mRNAs were confirmed as direct targets of the p53-induced miR-34a, miR-205 and miR-486-5p, respectively. In line with the loss of p53 function during tumor progression, elevated expression of HMGB1, KLF12 and CIT was detected in advanced stages of cancer. This study provides new insights and a comprehensive catalogue of p53-mediated regulations and p53 DNA binding in CRC cells.
Project description:Previous studies have evaluated the role of miRNAs in the initiation and progression of cancer. MiR-34a was found to be downregulated in several tumors, including medulloblastoma. We here analysed the function of miR-34a in vivo by targeted transgenesis to generate mice with constitutive deletion of the miR-34a gene, which resulted in the absence of mir-34a in all analysed tissues. Nevertheless, these mice were viable and fertile. A comprehensive standardized phenotypic analysis including more than 300 single parameters performed by the German Mouse Clinic revealed no apparent phenotype. Analysis of miR-34a expression in human medulloblastomas and medulloblastoma cell lines revealed significant downregulation as compared to human cerebellum. Re-expression of mir-34a in human medulloblastoma cells in vitro reduced cell viability, cell proliferation and induced apoptosis. Among the targets downregulated by miR-34a in human medulloblastoma cells were NMYC and SIRT1. Activation of the Shh pathway by targeted overexpression of SmoA1 causes medulloblastoma in mice, which is dependent on the presence and upregulation of NMYC. Analysis of miR-34a in ND2:SmoA1-derived medulloblastomas revealed significant suppression of miR-34a compared to normal cerebellum. Crossbreeding these mice with miR-34a knockout mice significantly accelerated medulloblastoma growth in mice deficient for miR-34a. Interestingly, NMYC and SIRT1 were highly expressed in medulloblastomas derived from these mice. We here demonstrate that miR-34a is dispensable for normal development, but that its loss accelerates medulloblastoma. Strategies aiming to re-express miR-34a in tumors could therefore represent an efficient therapy option.
Project description:We determined the effect of p53 activation on de novo protein synthesis using quantitative proteomics of newly synthesized proteins (pulsed stable isotope labeling with amino acids in cell culture, pSILAC) in combination with mRNA and non-coding RNA expression analyses by next generation sequencing (RNA-, miR-Seq) in the colorectal cancer (CRC) cell line SW480. Furthermore, genome-wide DNA binding of p53 was analyzed by chromatin-immunoprecipitation (ChIP-Seq). Thereby, we identified differentially regulated mRNAs (1258 up, 415 down), miRNAs (111 up, 95 down), lncRNAs (270 up, 123 down) and proteins (542 up, 569 down). Changes in mRNA and protein expression levels showed a positive correlation (r = 0.50, p < 0.0001). More transcriptionally induced genes displayed occupied p53 binding sites (4.3% mRNAs, 7.2% miRNAs, 6.3% lncRNAs, 5.9% proteins) than repressed genes (2.4% mRNAs, 3.2% miRNAs, 0.8% lncRNAs, 1.9% proteins), suggesting indirect mechanisms of repression. Around 50% of the downregulated proteins displayed seed-matching sequences of p53-induced miRNAs in the corresponding 3’-UTRs. Moreover, proteins repressed by p53 significantly overlapped with those previously shown to be repressed by miR-34a. We confirmed upregulation of the novel direct p53 target genes LINC01021, MDFI, ST14 and miR-486 and showed that ectopic LINC01021 expression inhibited proliferation in SW480 cells. Furthermore, HMGB1, KLF12 and CIT mRNAs were confirmed as direct targets of the p53-induced miR-34a, miR-205 and miR-486-5p, respectively. In line with the loss of p53 function during tumor progression, elevated expression of HMGB1, KLF12 and CIT was detected in advanced stages of cancer. This study provides new insights and a comprehensive catalogue of p53-mediated regulations and p53 DNA binding in CRC cells.
Project description:To address the in vivo relevance of CSF1R regulation by miR-34a during intestinal tumor formation, we generated ApcMin/+ mice with intestinal-epithelial cell (IEC)-specific deletions of the Mir34a and/or Csf1r genes. The mRNA expression profiles of intestinal adenomas with and without functional miR-34a and/or Csf1r were compared.
Project description:Previous studies have evaluated the role of miRNAs in the initiation and progression of cancer. MiR-34a was found to be downregulated in several tumors, including medulloblastoma. We here analysed the function of miR-34a in vivo by targeted transgenesis to generate mice with constitutive deletion of the miR-34a gene, which resulted in the absence of mir-34a in all analysed tissues. Nevertheless, these mice were viable and fertile. A comprehensive standardized phenotypic analysis including more than 300 single parameters performed by the German Mouse Clinic revealed no apparent phenotype. Analysis of miR-34a expression in human medulloblastomas and medulloblastoma cell lines revealed significant downregulation as compared to human cerebellum. Re-expression of mir-34a in human medulloblastoma cells in vitro reduced cell viability, cell proliferation and induced apoptosis. Among the targets downregulated by miR-34a in human medulloblastoma cells were NMYC and SIRT1. Activation of the Shh pathway by targeted overexpression of SmoA1 causes medulloblastoma in mice, which is dependent on the presence and upregulation of NMYC. Analysis of miR-34a in ND2:SmoA1-derived medulloblastomas revealed significant suppression of miR-34a compared to normal cerebellum. Crossbreeding these mice with miR-34a knockout mice significantly accelerated medulloblastoma growth in mice deficient for miR-34a. Interestingly, NMYC and SIRT1 were highly expressed in medulloblastomas derived from these mice. We here demonstrate that miR-34a is dispensable for normal development, but that its loss accelerates medulloblastoma. Strategies aiming to re-express miR-34a in tumors could therefore represent an efficient therapy option. For genome-wide expression analysis total RNA from brain and thymus of three or four male miR34a and four control mice was isolated using RNeasy Midi kit (Qiagen, Hilden, Germany). The cDNA microarrays were generated, hybridized and analysed as described (Horsch et al 2009). Two chip hybridizations were performed with total RNA for each individual mutant mouse against a reference RNA pool of the same organ.
Project description:To address the in vivo relevance of CSF1R regulation by miR-34a during intestinal tumor formation, we generated ApcMin/+ mice with intestinal-epithelial cell (IEC)-specific deletions of the Mir34a and/or Csf1r genes. The mRNA expression profiles of tumor organoids derived ffrom intestinal adenomas with and without functional miR-34a and/or Csf1r were compared.
Project description:Altered by defects in p53, epigenetic silencing, and genomic loss, the microRNA miR-34a represents one of the most clinically relevant tumor-suppressive microRNAs. Without question, a striking number of patients with cancer would benefit from miR-34a replacement, if poor miR-34a stability, non-specific delivery, and delivery-associated toxicity could be overcome. Here, we highlight a fully modified version of miR-34a (FM-miR-34a) that overcomes these hurdles when conjugated to a synthetically simplistic ligand. FM-miR-34a is orders of magnitude more stable than a partially modified version, without compromising its activity, leading to stronger repression of a greater number of miR-34a targets. FM-miR-34a potently inhibited proliferation and invasion, and induced sustained downregulation of endogenous target genes for >120 hours following in vivo delivery. In vivo targeting was achieved through conjugating FM-miR-34a conjugated to folate (FM-FolamiR-34a), which inhibited tumor growth leading to complete cures in some mice. These results have the ability to revitalize miR-34a as an anti-cancer agent, providing a strong rationale for clinical testing.
Project description:Recently, the p53-miR-34a network was identified to play an important role in tumorigenesis. As in acute myeloid leukemia with complex karyotype (CK-AML) TP53 alterations are the most common known molecular lesion, we further analyzed the p53-miR-34a axis in CK-AML with known TP53 status. Clinically, low miR-34a expression and TP53 alterations predicted for chemotherapy resistance and inferior outcome. Notably, in TP53unaltered CK-AML high miR-34a expression predicted for inferior overall survival (OS), whereas in TP53biallelic altered CK-AML high miR-34a expression pointed to better OS. To further investigate miR-34a-associated gene expression patterns, we analyzed distinct subgroups defined by TP53 alteration and miR-34a expression status. Exemplary samples from TP53unaltered (n=6) and TP53biallelic altered (n=6) CK-AML characterized by either high (CK+/miR-34ahigh expression, above median miR-34a expression of the entire cohort), or low (CK+/miR-34alow expression, below median miR-34a expression of the entire cohort) miR-34a expression (n=3 in each group), were analyzed. This molecular profiling linked impaired p53 to decreased miR-34a expression but also identified p53-independent miR-34a induction mechanisms, as shown in TP53biallelic altered cell lines treated with 15-deoxy-∆12,14-prostaglandin (PGJ2). An improved understanding of this mechanism might provide novel therapeutic options to restore miR-34a function and thereby induce cell cycle arrest and apoptosis in TP53altered CK-AML.
Project description:miR-34a is a known tumor suppressor that targets cell proliferation and apoptosis genes. In this study, we have shown that miR-34a acts as a safeguard for the inflammatory stem cell niche and reparative regeneration by modulating both the immune and epithelial responses to infection and inflammation. We isolated CD4+ T cells and colon epithelial cells from miR-34a-/- and wildtype mice revealed various changes in gene expression.