miR-181a sensitizes resistant leukaemia HL-60/Ara-C cells to Ara-C by inducing apoptosis.
BACKGROUND
Ara-C is one of the most commonly used drugs in the treatment of AML. However, the development of drug resistance always prevented its further use. It has been shown that miR-181a is associated with the clinical outcome of AML patients. Here, we investigated the possible role of miR-181a in AML Ara-C resistance.


METHODS
miR-181a expression was measured by real-time PCR. Cell viability was detected by MTT assay. Protein expressions were measured by western blotting. Caspase activity was examined by fluorescence assay.


RESULTS
We found that miR-181a expression was downregulated in the Ara-C-resistant cell line HL-60/Ara-C compared with its parental cell line HL-60. Overexpression of miR-181a in HL-60/Ara-C cells sensitized the cells to Ara-C treatment. Furthermore, Bcl-2 was confirmed as a direct miR-181a target by immunoblot analysis and reporter gene assays. Knockdown of Bcl-2 mimicked the effect of enforced miR-181a expression by reducing cell viability. In addition, the apoptosis pathway was activated by cytochrome C release and caspase 9/caspase 3 activation after miR-181a overexpression.


CONCLUSIONS
This study for the first time demonstrated that downregulation of miR-181a and upregulation of Bcl-2 in leukaemia cells confer resistance to Ara-C-based therapy. These results suggest that restoration of miR-181a expression might provide a promising therapeutic in drug resistance of leukaemia.
Department of Hematology, Shanghai Jiaotong University Affiliated Shanghai First People's Hospital, Shanghai, China. baihaitao@gmail.com
Haitao
H
Bai
Zhongwei
Z
Cao
Chong
C
Deng
Lili
L
Zhou
Chun
C
Wang
D020413:3' Untranslated Regions / Q000235:genetics; D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects* / Q000235:genetics*; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D015153:Blotting, Western; D020169:Caspases / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects / Q000235:genetics; D003561:Cytarabine / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D019008:Drug Resistance, Neoplasm / Q000235:genetics; D015973:Gene Expression Regulation, Leukemic; D057809:HEK293 Cells; D018922:HL-60 Cells; D006801:Humans; D015473:Leukemia, Promyelocytic, Acute / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D035683:MicroRNAs / Q000235:genetics*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism; D034622:RNA Interference; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012689:Sequence Homology, Nucleic Acid
D020413:3' Untranslated Regions; D000964:Antimetabolites, Antineoplastic; C540193:MIrn181 microRNA, human; D035683:MicroRNAs; D019253:Proto-Oncogene Proteins c-bcl-2; D003561:Cytarabine; D020169:Caspases