DNMT1 Inhibition Reprograms Pancreatic Cancer Stem Cells via Upregulation of the miR-17-92 Cluster.
Pancreatic ductal adenocarcinoma (PDAC) and other carcinomas are hierarchically organized, with cancer stem cells (CSC) residing at the top of the hierarchy, where they drive tumor progression, metastasis, and chemoresistance. As CSC and non-CSC share an identical genetic background, we hypothesize that differences in epigenetics account for the striking functional differences between these two cell populations. Epigenetic mechanisms, such as DNA methylation, play an important role in maintaining pluripotency and regulating the differentiation of stem cells, but the role of DNA methylation in pancreatic CSC is obscure. In this study, we investigated the genome-wide DNA methylation profile of PDAC CSC, and we determined the importance of DNA methyltransferases for CSC maintenance and tumorigenicity. Using high-throughput methylation analysis, we discovered that sorted CSCs have a higher level of DNA methylation, regardless of the heterogeneity or polyclonality of the CSC populations present in the tumors analyzed. Mechanistically, CSC expressed higher DNMT1 levels than non-CSC. Pharmacologic or genetic targeting of DNMT1 in CSCs reduced their self-renewal and in vivo tumorigenic potential, defining DNMT1 as a candidate CSC therapeutic target. The inhibitory effect we observed was mediated in part through epigenetic reactivation of previously silenced miRNAs, in particular the miR-17-92 cluster. Together, our findings indicate that DNA methylation plays an important role in CSC biology and also provide a rationale to develop epigenetic modulators to target CSC plasticity and improve the poor outcome of PDAC patients. Cancer Res; 76(15); 4546-58. ©2016 AACR.
Stem Cells in Cancer & Ageing, Barts Cancer Institute, Queen Mary University of London, London, United Kingdom. Stem Cells & Cancer Group, Spanish National Cancer Research Centre (CNIO), Madrid, Spain.
Sladjana
S
Zagorac
Stem Cells & Cancer Group, Spanish National Cancer Research Centre (CNIO), Madrid, Spain. Department of Biochemistry, Universidad Autónoma de Madrid, Instituto de Investigaciones Biomédicas "Alberto Sols" CSIC-UAM, Madrid, Spain.
Sonia
S
Alcala
Cancer Epigenetics Unit, Asturias Central University Hospital, Spanish Council for Scientific Research (CSIC), Oviedo, Spain.
Gustavo
G
Fernandez Bayon
Stem Cells in Cancer & Ageing, Barts Cancer Institute, Queen Mary University of London, London, United Kingdom.
Tony
T
Bou Kheir
Stem Cells in Cancer & Ageing, Barts Cancer Institute, Queen Mary University of London, London, United Kingdom.
Matthieu
M
Schoenhals
Human Genotyping-Cegen Unit, Spanish National Cancer Research Centre (CNIO), Madrid, Spain.
Anna
A
González-Neira
Cancer Epigenetics Unit, Asturias Central University Hospital, Spanish Council for Scientific Research (CSIC), Oviedo, Spain.
Mario
M
Fernandez Fraga
Stem Cells in Cancer & Ageing, Barts Cancer Institute, Queen Mary University of London, London, United Kingdom. Stem Cells & Cancer Group, Spanish National Cancer Research Centre (CNIO), Madrid, Spain.
Alexandra
A
Aicher
Stem Cells in Cancer & Ageing, Barts Cancer Institute, Queen Mary University of London, London, United Kingdom. Stem Cells & Cancer Group, Spanish National Cancer Research Centre (CNIO), Madrid, Spain. c.heeschen@qmul.ac.uk.
Christopher
C
Heeschen
Stem Cells & Cancer Group, Spanish National Cancer Research Centre (CNIO), Madrid, Spain. Department of Biochemistry, Universidad Autónoma de Madrid, Instituto de Investigaciones Biomédicas "Alberto Sols" CSIC-UAM, Madrid, Spain.
Bruno
B
Sainz
D000230:Adenocarcinoma / Q000235:genetics* / Q000473:pathology; D021441:Carcinoma, Pancreatic Ductal / Q000235:genetics* / Q000473:pathology; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000037:antagonists & inhibitors* / Q000235:genetics*; D006801:Humans; D035683:MicroRNAs / Q000235:genetics*; D014411:Neoplastic Stem Cells / Q000378:metabolism* / Q000473:pathology; D062085:RNA, Long Noncoding; D015854:Up-Regulation
C568997:MIR17HG, human; D035683:MicroRNAs; D062085:RNA, Long Noncoding; D004248:DNA (Cytosine-5-)-Methyltransferases