Expression of miR-196b is not exclusively MLL-driven but is especially linked to activation of HOXA genes in pediatric acute lymphoblastic leukemia
Diana Schotte, Ellen A.M. Lange-Turenhout, Dominique J.P.M. Stumpel, Ronald W. Stam, Jessica G.C.A.M. Buijs-Gladdines, Jules P.P. Meijerink, Rob Pieters, Monique L. Den Boer

Author Affiliations

  1. Diana Schotte,
  2. Ellen A.M. Lange-Turenhout,
  3. Dominique J.P.M. Stumpel,
  4. Ronald W. Stam,
  5. Jessica G.C.A.M. Buijs-Gladdines,
  6. Jules P.P. Meijerink,
  7. Rob Pieters and
  8. Monique L. Den Boer
  1. Department of Pediatric Oncology and Hematology, Erasmus MC/Sophia Children's Hospital, Erasmus University Medical Center Rotterdam, the Netherlands
  1. Correspondence: Monique L. den Boer, PhD, MSc, Erasmus MC-Sophia Children’s Hospital, Dept. of Pediatric, Oncology and Hematology, Room Sp2456 P.O. Box 2060 3000 CB Rotterdam the Netherlands. E-mail: m.l.denboer{at}erasmusmc.nl
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Abstract

Background Deregulation of microRNA may contribute to hematopoietic malignancies. MicroRNA-196b (miR-196b) is highly expressed in MLL-rearranged leukemia and has been shown to be activated by MLL and MLL-fusion genes.

Design and Methods In order to determine whether high expression of miR-196b is restricted to MLL-rearranged leukemia, we used quantitative stem-loop reverse transcriptase polymerase chain reaction to measure the expression of this microRNA in 72 selected cases of pediatric acute lymphoblastic leukemia i.e. MLL-rearranged and non-MLL-rearranged precursor B-cell and T-cell acute lymphoblastic leukemias. We also determined the expression of HOXA-genes flanking miR-196 by microarray and real-time quantitative polymerase chain reaction. Furthermore, we used CpG island-arrays to explore the DNA methylation status of miR-196b and HOXA.

Results We demonstrated that high expression of miR-196b is not unique to MLL-rearranged acute lymphoblastic leukemia but also occurs in patients with T-cell acute lymphoblastic leukemia patients carrying CALM-AF10, SET-NUP214 and inversion of chromosome 7. Like MLL-rearrangements, these abnormalities have been functionally linked with up-regulation of HOXA. In correspondence, miR-196b expression in these patients correlated strongly with the levels of HOXA family genes (Spearman’s correlation coefficient ≥ 0.7; P≤0.005). Since miR-196b is encoded on the HOXA cluster, these data suggest co-activation of miR-196b and HOXA genes in acute lymphoblastic leukemia. Up-regulation of miR-196b coincides with reduced DNA methylation at CpG islands in the promoter regions of miR-196b and the entire HOXA cluster in MLL-rearranged cases compared to in cases of non-MLL precursor B-cell acute lymphoblastic leukemia and normal bone marrow (P<0.05), suggesting an epigenetic origin for miR-196b over-expression. Although patients with MLL-rearranged acute lymphoblastic leukemia are highly resistant to prednisolone and L-asparaginase, this resistance was not attributed to miR-196b expression.

Conclusions High expression of miR-196b is not exclusively MLL-driven but can also be found in other types of leukemia with aberrant activation of HOXA genes. Since miR-196b has been shown by others to exert oncogenic activity in bone marrow progenitor cells, the findings of the present study imply a potential role for miR-196b in the underlying biology of all HOXA-activated leukemias.

  • Received February 4, 2010.
  • Revision received April 23, 2010.
  • Accepted May 17, 2010.
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