Project description:The miR-29 family is an important player in the molecular pathophysiology of distinct types of cancer, with roles that seems to depend on cellular context. Reduced miR-29 levels are associated with more aggressive disease and its overexpression in cancer and leukemic cell lines inhibits proliferation. In contrast, its overexpression in hematopoietic progenitors, promotes leukemogenesis. We explored the potential roles of miR-29a in the molecular pathophysiology of T-cell acute lymphoblastic leukemia (T-ALL). As compared to normal T-cells, miR-29a levels are extremely reduced in T-ALL and in the Jurkat cell line. Microarrays analysis in Jurkat cells, following the introduction of synthetic miR-29a mimics, revealed the down-regulation of several predicted targets, including previously described targets (DNMT3a/b, CDK6, PXDN, MCL1, PIK3R1 and CXXC6), and novel targets with roles in active DNA demethylation, such as members of the ten-eleven-translocation (TET) family and TDG. Reduced miR-29a levels contribute to altered epigenetics, as its introduction in Jurkat cells, promotes the demethylation of the AHR gene (commonly methylated in T-ALL). In T-ALL patients, miR-29a levels are significantly associated with blast counts and disease free survival. Our results highlight the relevance of miR-29 in T-ALL physiopathology, and may help to clarify some contrasting findings reported in the literature. In order to identify potential miR-29a targets in T-cell lymphoblastic leukemia, Jurkat cells were electroporated with synthetic RNA molecules corresponding to miR-29a mimics (pre-miR) or inhibitors (anti-miR); and microarray profiles were compared to the profiles of Jurkat cells eletroporated with the corresponding negative controls. Transcripts with levels reduced following the introduction of the pre-miR-29a (as compared to pre-miR-Control), or transcripts acumulated folowing introduction of the anti-miR-29a inhibitor (as compared to anti-miR-Control), were considered potential targets; and were further compared to microRNA target prediction databases. Two paired samples were used for this analysis.

Project description:Background: MicroRNAs are regulators of gene expression, mainly functioning by decreasing mRNA levels of their multiple targets. Deregulated microRNA expression has been shown for acute myeloid leukemia, a disease also characterized by altered gene expression associated with distinct genomic aberrations such as nucleophosmin (NPM1) mutations. To further illuminate the role of deregulated microRNA and gene expression in cytogenetically normal acute myeloid leukemia with NPM1 mutation, we performed an integrative analysis of microRNA and mRNA expression data sets. Design and Methods: Both microRNA and gene expression profiles were measured in a cohort of 43 adult acute myeloid leukemia patient samples (n=42 cytogenetically normal, n=1 del7q; median age 46 years [range 23-60]) of known NPM1 mutation status (n=23 mutated, n=20 wild-type) and data integratively analyzed. Putative microRNA-mRNA interactions were validated by quantitative RT-PCR, Western Blot and luciferase reporter assays. For selected microRNAs, sensitivity of microRNA-overexpressing cells to cytarabine treatment was tested by FACS viability and cell proliferation assays. Results: Our integrative approach of analyzing both microRNA and gene expression profiles in parallel resulted in a refined list of putative target genes affected by NPM1 mutation-associated microRNA deregulation. Of 177 putative microRNA - target mRNA interactions, we could identify and validate 77 novel candidates with known or potential implication in leukemogenesis, such as IRF2-miR-20a, KIT-miR-20a and MN1-miR-15a. Furthermore, our data showed that deregulated expression of tumor suppressor microRNAs such as miR-29a and miR-30c might contribute to the sensitivity to cytarabine, which is observed in NPM1-mutated acute myeloid leukemia. Conclusions: Overall, our observations highlight that integrative data analysis approaches can improve insights into leukemia biology, and lead to the identification of novel microRNA - target gene interactions of potential relevance for acute myeloid leukemia treatment. MicroRNA and gene expression profiles were measured in a cohort of 43 adult (42 cytogenetically normal and 1 del7q) acute myeloid leukemia patient samples of known NPM1 mutation status (n=23 mutated, n=20 wild-type). This submission represents the mRNA expression component of the study. The miRNA expression data will be deposited as supplementary information along with the accompanying manuscript.

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