Epigenetic silencing of the tumor suppressor microRNA Hsa-miR-124a regulates CDK6 expression and confers a poor prognosis in acute lymphoblastic leukemia.
Whereas transcriptional silencing of genes due to epigenetic mechanisms is one of the most important alterations in acute lymphoblastic leukemia (ALL), some recent studies indicate that DNA methylation contributes to down-regulation of miRNAs during tumorigenesis. To explore the epigenetic alterations of miRNAs in ALL, we analyzed the methylation and chromatin status of the miR-124a loci in ALL. Expression of miR-124a was down-regulated in ALL by hypermethylation of the promoter and histone modifications including decreased levels of 3mk4H3 and AcH3 and increased levels of 2mK9H3, 3mK9H3, and 3mK27H3. Epigenetic down-regulation of miR-124a induced an up-regulation of its target, CDK6, and phosphorylation of retinoblastoma (Rb) and contributed to the abnormal proliferation of ALL cells both in vitro and in vivo. Cyclin-dependent kinase 6 (CDK6) inhibition by sodium butyrate or PD-0332991 decreased ALL cell growth in vitro, whereas overexpression of pre-miR124a led to decreased tumorigenicity in a xenogeneic in vivo Rag2(-/-)gammac(-/-) mouse model. The clinical implications of these findings were analyzed in a group of 353 patients diagnosed with ALL. Methylation of hsa-miR-124a was observed in 59% of the patients, which correlated with down-regulation of miR-124a (P < 0.001). Furthermore, hypermethylation of hsa-miR-124a was associated with higher relapse rate (P = 0.001) and mortality rate (P < 0.001), being an independent prognostic factor for disease-free survival (P < 0.001) and overall survival (P = 0.005) in the multivariate analysis. These results provide the grounds for new therapeutic strategies in ALL either targeting the epigenetic regulation of microRNAs and/or directly targeting the CDK6-Rb pathway.
Hematology Department and Area of Cell Therapy, Clinica Universitaria and Division of Gene Therapy and Hepatology, Foundation for Applied Medical Research, University of Navarra, Pamplona, Spain.
Xabier
X
Agirre
Amaia
A
Vilas-Zornoza
Antonio
A
Jiménez-Velasco
José Ignacio
JI
Martin-Subero
Lucia
L
Cordeu
Leire
L
Gárate
Edurne
E
San José-Eneriz
Gloria
G
Abizanda
Paula
P
Rodríguez-Otero
Puri
P
Fortes
José
J
Rifón
Eva
E
Bandrés
María José
MJ
Calasanz
Vanesa
V
Martín
Anabel
A
Heiniger
Antonio
A
Torres
Reiner
R
Siebert
José
J
Román-Gomez
Felipe
F
Prósper
D000818:Animals; D002455:Cell Division; D045744:Cell Line, Tumor; D002843:Chromatin / Q000235:genetics / Q000502:physiology; D051361:Cyclin-Dependent Kinase 6 / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000172:deficiency / Q000235:genetics; D004195:Disease Models, Animal; D018572:Disease-Free Survival; D015536:Down-Regulation; D044127:Epigenesis, Genetic / Q000235:genetics*; D005260:Female; D020868:Gene Silencing; D006801:Humans; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D035683:MicroRNAs / Q000235:genetics*; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000235:genetics* / Q000401:mortality / Q000473:pathology; D011379:Prognosis; D012333:RNA, Messenger / Q000235:genetics; D015996:Survival Rate; D014158:Transcription, Genetic
D002843:Chromatin; D004268:DNA-Binding Proteins; C509207:MIRN124 microRNA, human; D035683:MicroRNAs; D012333:RNA, Messenger; C499308:Rag2 protein, mouse; C495911:CDK6 protein, human; D051361:Cyclin-Dependent Kinase 6