MicroRNA-155 as an inducer of apoptosis and cell differentiation in Acute Myeloid Leukaemia.
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.
Catalina A
CA
Palma
Dima
D
Al Sheikha
Teck Khai
TK
Lim
Adam
A
Bryant
Thi Thanh
TT
Vu
Vivek
V
Jayaswal
Blood, Stem Cells and Cancer Research, St Vincent's Centre for Applied Medical Research, St Vincent's Hospital, Sydney, Australia. a.lafferty@amr.org.au.
David D F
DD
Ma
D015703:Antigens, CD / Q000235:genetics / Q000378:metabolism; D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D053148:Caspase 3 / Q000235:genetics / Q000378:metabolism; D002454:Cell Differentiation / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D003561:Cytarabine / Q000494:pharmacology; D044127:Epigenesis, Genetic; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic; D018922:HL-60 Cells; D006801:Humans; D015470:Leukemia, Myeloid, Acute / Q000235:genetics* / Q000378:metabolism / Q000401:mortality / Q000473:pathology; D035683:MicroRNAs / Q000235:genetics* / Q000378:metabolism; D009154:Mutation; D009363:Neoplasm Proteins / Q000235:genetics* / Q000378:metabolism; D015398:Signal Transduction; D016019:Survival Analysis; D014407:Tumor Cells, Cultured; D051941:fms-Like Tyrosine Kinase 3 / Q000235:genetics* / Q000378:metabolism
D015703:Antigens, CD; D000964:Antimetabolites, Antineoplastic; C524942:MIRN155 microRNA, human; D035683:MicroRNAs; D009363:Neoplasm Proteins; D003561:Cytarabine; C497970:FLT3 protein, human; D051941:fms-Like Tyrosine Kinase 3; D053148:Caspase 3