Priority Research Papers:
A genome-wide miRNA screen revealed miR-603 as a MGMT-regulating miRNA in glioblastomas
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Deepa Kushwaha1,*, Valya Ramakrishnan2,*, Kimberly Ng1, Tyler Steed2 ,Thien Nguyen2, Diahnn Futalan2, Johnny C. Akers2, Jann Sarkaria3, Tao Jiang4, Dipanjan Chowdhury1, Bob S. Carter2 and Clark C. Chen2
1 Dept. of Radiation Oncology, Dana-Farber Cancer Institute, Boston, MA
2 Center for Theoretical and Applied Neuro-Oncology, Moores Cancer Center, Division of Neurosurgery, University of California San Diego, San Diego, CA
3 Mayo Clinic, Department of Radiation Oncology, Rochester, MN
4 Department of Neurosurgery, Tiantan Medical Center, Beijing, China
* These authors contributed equally as first authors
Clark Chen, email:
Keywords: microRNA, Glioblastoma, MGMT, Temozolomide, miRNA cooperativity
Received: May 5, 2014 Accepted: May 12, 2014 Published: May 14, 2014
MGMT expression is a critical determinant for therapeutic resistance to DNA alkylating agents. We previously demonstrated that MGMT expression is post-transcriptionally regulated by miR-181d and other miRNAs. Here, we performed a genome-wide screen to identify MGMT regulating miRNAs. Candidate miRNAs were further tested for inverse correlation with MGMT expression in clinical specimens. We identified 15 candidate miRNAs and characterized the top candidate, miR-603. Transfection of miR-603 suppressed MGMT mRNA/protein expression in vitro and in vivo; this effect was reversed by transfection with antimiR-603. miR-603 affinity-precipitated with MGMT mRNA and suppressed luciferase activity in an MGMT-3’UTR-luciferase assay, suggesting direct interaction between miR-603 and MGMT 3’UTR. miR-603 transfection enhanced the temozolomide (TMZ) sensitivity of MGMT-expressing glioblastoma cell lines. Importantly, miR-603 mediated MGMT suppression and TMZ resistance were reversed by expression of an MGMT cDNA. In a collection of 74 clinical glioblastoma specimens, both miR-603 and miR-181d levels inversely correlated with MGMT expression. Moreover, a combined index of the two miRNAs better reflected MGMT expression than each individually. These results suggest that MGMT is co-regulated by independent miRNAs. Characterization of these miRNAs should contribute toward strategies for enhancing the efficacy of DNA alkylating agents.
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