Table of Contents
Journal of Cancer Research
Volume 2013 (2013), Article ID 452809, 6 pages
http://dx.doi.org/10.1155/2013/452809
Research Article

The Breakage-Fusion-Bridge Cycle Producing MLL Amplification in a Case of Myelodysplastic Syndrome

1Victorian Cancer Cytogenetics Service, St Vincent’s Hospital, P.O. Box 2900, Fitzroy, VIC 3065, Australia
2Department of Medicine, St Vincent’s Hospital, University of Melbourne, Fitzroy, VIC 3065, Australia

Received 23 May 2013; Accepted 24 June 2013

Academic Editor: Mario Scartozzi

Copyright © 2013 Lan Ta et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Telomere loss may lead to chromosomal instability via the breakage-fusion-bridge (BFB) cycle which can result in genetic amplification and the formation of ring and dicentric chromosomes. This cycle continues until stable chromosomes are formed. The case of a 72-year-old female with refractory anaemia with excess blasts type 2 illustrates these events. Conventional cytogenetics produced a complex karyotype which included unstable abnormalities of chromosomes 11, 12, and 15. Fluorescence in situ hybridization (FISH) analyses including multicolor-FISH (M-FISH) and multicolor-banding (M-BAND) revealed multiple clonal populations with 5 copies of MLL on either a ring chromosome composed entirely of chromosome 11 material or a derivative chromosome composed of chromosomes 11, 12, and 15. The FISH results also clarified the likely evolution of the karyotypic complexity. The simplest cell line contained a dic(12;15) in addition to copy number aberrations that are typical of MDS or AML. As the disease progressed, a ring 11 was formed. Subsequently, the ring 11 appears to have unwound and inserted itself into the dic(12;15) chromosome followed by an inversion of the derivative chromosome, producing a der(11;15;12). Telomeric loss and BFB cycles appear to have played an important role in the chromosomal rearrangements and clonal evolution demonstrated in the karyotype.