- Keynote lecture presentation
- Open Access
3D nuclear organization and genomic instability in cancer
BMC Proceedings volume 7, Article number: K17 (2013)
To understand the genetic changes that occur at tumor initiation and during tumor progression, we focus on changes in nuclear architecture that promote the onset of genomic instability [1, 2]. To determine changes in nuclear organization, we measure the 3D nuclear organization of telomeres, the ends of chromosomes. The measurements of telomeres allow one to trace the positions of chromosomes in interphase nuclei and, by using a fluorescent telomere-specific probe, all telomeres can be visualized in a single image.
During the past years, we have defined the organization of telomeres in nuclei of normal, immortalized and tumor cells. We have developed quantitative software that enables us to measure the three-dimensional (3D) organization of telomeres [3, 4]. The parameters we measure include: number of telomeres, sizes of telomeres, nuclear distribution of telomeres, and the presence of telomeric aggregates. The latter are clusters of telomeres that are absent from normal cells. More recently, we started to automate the 3D image acquisition and analysis and we are able to scan 15 000 cells per hour .
We observed changes in the nuclear organization of telomeres as a result of conditional c-Myc deregulation dependent on a functional myc box II [6, 7]. We found Epstein-Barr Virus-induced changes in 3D telomere organization and resulting genomic instability .
Encouraged by these findings, we focused on tumor initiation and progression in patient samples and observed cancer-associated 3D nuclear telomere changes in lymphoid and solid tumors [9–12]. Moreover, the use of 3D nuclear telomere profiling permitted, for the first time, the identification of patient (and tumor) subpopulations that were not detectable up to that point. For example, we blindly defined three distinct subpopulations that correlated with short-term, intermediate and long-term survival in glioblastoma . Using the same 3D imaging approach, we defined subpopulations in myelodysplastic syndromes and acute myeloid leukemias . Additional studies are currently ongoing.
We provided evidence that genomic instability is a result of these nuclear changes. Dynamic nuclear alterations directly result from 3D telomere aberrations [1, 2, 6, 13–15]. These genomic changes include aneuploidy, Robertsonian fusions, breakage-bridge fusion (BBF) cycles with resulting terminal deletions and unbalanced translocations and continued rounds of BBF cycles. While these changes can be followed during cancer progression in patients, their true origin can only be examined in conditional expression studies or longitudinally in mouse models. Using conditional c-Myc deregulation, we demonstrated that changes in 3D telomere profiles precede the onset and propagation of genomic instability [6, 13].
In Hodgkin’s lymphoma, in collaboration with Dr. Hans Knecht, we showed that mono-nucleated H cells become multinucleated Reed Sternberg (RS) cells through telomere dysfunction as measured by 3D nuclear profiles [10, 16]. These changes coincide with localized shelterin dysfunction, aberrant centrosome duplication as well as spindle formation and significantly elevated levels of DNA damage foci [10, 16]. Spectral karyotyping (SKY) and super resolution 3D imaging confirmed the dynamics and complexity of these genetic changes in which RS cells are the end-stage cells generated through multiple defects traced back to the H cells and propagated from there on . Most recently, we have reported that Hodgkin’s patients with recurrent/non-recurrent disease display distinct 3D telomeric profiles .
Ongoing studies focus on a variety of cancers where clinicians currently lack the ability to define the risk of an individual patient to progress, the ability of early detection or of monitoring of disease progression. In conclusion, 3D telomere profiling provides a platform technology able to determine normal and aberrant nuclear organization that is a measure of genomic instability and cancer.
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Caporali A, Wark L, Vermolen BJ, Garini Y, Mai S: Telomeric aggregates and end-to-end chromosomal fusions require myc box II. Oncogene. 2007, 26 (10): 1398-406. 10.1038/sj.onc.1209928.
Lacoste S, Wiechec E, Dos Santos Silva AG, Guffei A, Williams G, Lowbeer M, Benedek K, Henriksson M, Klein G, Mai S: Chromosomal rearrangements after ex vivo Epstein-Barr virus (EBV) infection of human B cells. Oncogene. 2010, 29 (4): 503-15. 10.1038/onc.2009.359.
Mai S, Garini Y: The significance of telomeric aggregates in the interphase nuclei of tumor cells. J Cell Biochem. 2006, 97 (5): 904-15. 10.1002/jcb.20760.
Knecht H, Sawan B, Lichtensztejn D, Lemieux B, Wellinger RJ, Mai S: The 3D nuclear organization of telomeres marks the transition from Hodgkin to Reed-Sternberg cells. Leukemia. 2009, 23 (3): 565-73. 10.1038/leu.2008.314.
Gadji M, Fortin D, Tsanaclis AM, Garini Y, Katzir N, Wienburg Y, Yan J, Klewes L, Klonisch T, Drouin R, Mai S: Three-dimensional nuclear telomere architecture is associated with differential time to progression and overall survival in glioblastoma patients. Neoplasia. 2010, 12 (2): 183-91.
Gadji M, Adebayo Awe J, Rodrigues P, Kumar R, Houston DS, Klewes L, Dièye TN, Rego EM, Passetto RF, de Oliveira FM, Mai S: Profiling three-dimensional nuclear telomeric architecture of myelodysplastic syndromes and acute myeloid leukemia defines patient subgroups. Clin Cancer Res. 2012, 18 (12): 3293-304. 10.1158/1078-0432.CCR-12-0087.
Mai S, Garini Y: Oncogenic remodeling of the three-dimensional organization of the interphase nucleus: c-Myc induces telomeric aggregates whose formation precedes chromosomal rearrangements. Cell Cycle. 2005, 4 (10): 1327-31. 10.4161/cc.4.10.2082.
Guffei A, Lichtensztejn Z, Gonçalves Dos Santos Silva A, Louis SF, Caporali A, Mai S: c-Myc-dependent formation of Robertsonian translocation chromosomes in mouse cells. Neoplasia. 2007, 9 (7): 578-88. 10.1593/neo.07355.
Guffei A, Sarkar R, Klewes L, Righolt C, Knecht H, Mai S: Dynamic chromosomal rearrangements in Hodgkin's lymphoma are due to ongoing three-dimensional nuclear remodeling and breakage-bridge-fusion cycles. Haematologica. 2010, 95 (12): 2038-46. 10.3324/haematol.2010.030171.
Knecht H, Sawan B, Lichtensztejn Z, Lichtensztejn D, Mai S: 3D Telomere FISH defines LMP1-expressing Reed-Sternberg cells as end-stage cells with telomere-poor 'ghost' nuclei and very short telomeres. Lab Invest. 2010, 90 (4): 611-9. 10.1038/labinvest.2010.2.
Knecht H, Kongruttanachok N, Sawan B, Brossard J, Prévost S, Turcotte E, Lichtensztejn Z, Lichtensztejn D, Mai S: Three-dimensional Telomere Signatures of Hodgkin- and Reed-Sternberg Cells at Diagnosis Identify Patients with Poor Response to Conventional Chemotherapy. Transl Oncol. 2012, 5 (4): 269-77.
We thank the Canada Foundation for Innovation, the Canadian Institutes of Health Research, CancerCare Manitoba, and the Terry Fox Research Institute for grant funding and all patients for their support of this study.
There are no competing interests in this presentation.