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Presence of alternative lengthening of telomeres associated circular extrachromosome telomere repeats in primary leukemia cells of chronic myeloid leukemia

Oumar Samassekou1, Abba Malina2, Josée Hébert3 and Ju Yan1*

Author Affiliations

1 Division of Genetics, Department of Pediatrics, Faculty of Medicine and Health Sciences, Université de Sherbrooke, 3001, 12th Avenue North, Sherbrooke, QC J1H 5N4, Canada

2 Department of Biochemistry, McGill University, 3655 Promenade Sir William Osler, Montreal, QC, H3G 1Y6, Canada

3 Leukemia Cell Bank of Quebec, and Division of Hematology-Oncology, Maisonneuve-Rosemont Hospital, 5415 Boul. de l’Assomption, Montréal, QC, H1T 2M4, Canada

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Journal of Hematology & Oncology 2013, 6:26  doi:10.1186/1756-8722-6-26

Published: 2 April 2013



The predominant mechanism by which human tumors maintain telomere length is via telomerase. In ~10% of tumor samples, however, telomere length is conserved, despite no detectable telomerase activity, in part through activation of the alternative lengthening of telomeres (ALT) pathway.


We studied the circular extra-chromosomal telomeric repeat (ECTR), an ALT hallmark, and telomerase activity in 24 chronic myeloid leukemia (CML) patients in chronic phase (CP).


We identified the presence of ECTR in primary leukemia cells from some of these samples, which indicates the possible involvement of an ALT mechanism. Moreover, we found that some samples exhibited both circular ECTR and telomerase activities, suggesting that both mechanisms can contribute to the onset of CML.


We propose that ALT or the combined activities of ALT and telomerase might be required for the early stages of leukemogenesis. These findings shed new light into the oncogenic pathways responsible for the maintenance of telomere length in leukemia, which will ultimately determine the effectiveness of anti-telomerase-based treatment protocols.

CML; Telomeres; Cancer biology