RESUMEN
BACKGROUND: Acute myeloid leukaemia (AML) is characterised by the halt in maturation of myeloid progenitor cells, combined with uncontrolled proliferation and abnormal survival, leading to the accumulation of immature blasts. In many subtypes of AML the underlying causative genetic insults are not fully described. MicroRNAs are known to be dysregulated during oncogenesis. Overexpression of miR-155 is associated with some cancers, including haematological malignancies, and it has been postulated that miR-155 has an oncogenic role. This study investigated the effects of modulating miR-155 expression in human AML cells, and its mechanism of action. RESULTS: Analysis of miR-155 expression patterns in AML patients found that Fms-like tyrosine kinase 3 (FLT3)-wildtype AML has the same expression level as normal bone marrow, with increased expression restricted to AML with the FLT3-ITD mutation. Induction of apoptosis by cytarabine arabinoside or myelomonocytic differentiation by 1,23-dihydroxyvitaminD3 in FLT3-wildtype AML cells led to upregulated miR-155 expression. Knockdown of miR-155 by locked nucleic acid antisense oligonucleotides in the FLT3-wildtype AML cells conferred resistance to cytarabine arabinoside induced apoptosis and suppressed the ability of cells to differentiate.Ectopic expression of miR-155 in FLT3-wildtype AML cells led to a significant gain of myelomonocytic markers (CD11b, CD14 and CD15), increase in apoptosis (AnnexinV binding), decrease in cell growth and clonogenic capacity.In silico target prediction identified a number of putative miR-155 target genes, and the expression changes of key transcription regulators of myeloid differentiation and apoptosis (MEIS1, GF1, cMYC, JARID2, cJUN, FOS, CTNNB1 and TRIB2) were confirmed by PCR. Assessment of expression of apoptosis-related proteins demonstrated a marked increase in cleaved caspase-3 expression confirming activation of the apoptosis cascade. CONCLUSIONS: This study provides evidence for an anti-leukaemic role for miR-155 in human FLT3-wildtype AML, by inducing cell apoptosis and myelomonocytic differentiation, which is in contrast to its previously hypothesized role as an oncogene. This highlights the complexity of gene regulation by microRNAs that may have tumour repressor or oncogenic effects depending on disease context or tissue type.
Asunto(s)
Epigénesis Genética , Leucemia Mieloide Aguda/genética , MicroARNs/genética , Proteínas de Neoplasias/genética , Tirosina Quinasa 3 Similar a fms/genética , Antígenos CD/genética , Antígenos CD/metabolismo , Antimetabolitos Antineoplásicos/farmacología , Apoptosis/efectos de los fármacos , Caspasa 3/genética , Caspasa 3/metabolismo , Diferenciación Celular/efectos de los fármacos , Proliferación Celular/efectos de los fármacos , Citarabina/farmacología , Perfilación de la Expresión Génica , Regulación Neoplásica de la Expresión Génica , Células HL-60 , Humanos , Leucemia Mieloide Aguda/metabolismo , Leucemia Mieloide Aguda/mortalidad , Leucemia Mieloide Aguda/patología , MicroARNs/metabolismo , Mutación , Proteínas de Neoplasias/metabolismo , Transducción de Señal , Análisis de Supervivencia , Células Tumorales Cultivadas , Tirosina Quinasa 3 Similar a fms/metabolismoRESUMEN
The efficient synthesis of homogeneous MUC1 peptide oligomers using sequential ligation reactions in the N-to-C and C-to-N directions is reported. The bi-directional ligation strategy makes use of thioester formation via N â S acyl shift chemistry in combination with peptide ligation reactions and was used to prepare a library of peptide oligomers ranging in molecular mass from 3.8-9.4 kDa, comprised of between 2 and 5 repeats of the MUC1 variable number tandem repeat sequence.