2009 Vienna - European Society of Human Genetics

Cancer cytogenetics
P07.08
molecular cytogenetic study of oligodendroglial tumors
L. Lizcova 1 , Z. Zemanova 1 , F. Kramar 2 , S. Ransdorfova 3 , P. Hrabal 4 , K. Michalova
1 ;
1 Center of Oncocytogenetics, General Teaching Hospital and 1st Faculty of
Medicine, Charles University, Prague, Czech Republic, 2 Department of Neurosurgery,
Central Military Hospital and 1st Faculty of Medicine, Charles University,
Prague, Czech Republic, 3 Institute of Hematology and Blood Tranfusion,
Prague, Czech Republic, 4 Department of Pathology, Central Military Hospital,
Prague, Czech Republic.
In oligodendroglial tumors, loss of genetic material on chromosomomes
1p and 19q has been shown to predict better therapeutic response and
longer survival. However, the significance of additional chromosomal
aberrations has not been considered.
For detection of the 1p36 and 19q13 deletion and other chromosomal
rearrangements in oligodendroglial cells, we performed dual-color
interphase fluorescence in situ hybridization (I-FISH) with locus-specific
DNA probes (Abbott Laboratories), 200 isolated whole cell nuclei
(prepared from fresh non-fixed tumor tissue) were analyzed for each
probe.
We examined 35 patients with histologically confirmed oligodendroglial
tumors (10x oligodendroglioma, 19x anaplastic oligodendroglioma,
6x anaplastic oligoastrocytoma). Deletion of 1p36 and 19q13 region
was detected in 28 cases (80%). In 12 of them combined deletion was
found as a sole cytogenetic abnormality. Median of progression free
survival (PFS) in this group was 47 months and only one patient died.
In other 16 cases additional chromosomal rearrangements typical for
high-grade gliomas were proved. In these patients significantly worse
PFS was conferred (27 months, 6 patients died).
Genetic studies increase our understanding of oligodendrogliomas.
Although, deletion of 1p/19q was shown as a powerful favourable
prognostic marker, our study demonstrates that prognosis is influenced
by additional chromosomal aberrations. Further comprehensive
whole-genome analyses of larger series with sufficient follow-up are
needed to prove real prognostic significance and nonrandomness of
these aberrations.
Supported by MZO VFN2005 and MSM LC535
P07.09
Retinoblastoma in monozygotic twins due to deletion of Rb gene
O. Messina 1 , M. Arroyo 2 , F. Perez 2 , L. Gonzalez 2 , S. Cuevas 3 ;
1 Hospital General de Mexico, Mexico d.f., Mexico, 2 Hospital General de Mexico,
Mexico D.F., Mexico, 3 Hospital General de Mexico, Universidad Nacional Autonoma
de Mexico, Mexico D.F., Mexico.
Retinoblastoma (Rb) is the most common malignant tumor of the developing
retina in children and occurs between 1 in 13,500 and 1 in
25,000 new born. In general, diagnosis is done at age of 12 month in
bilateral cases and at age of 18 months in unilateral cases. Leukocoria,
strabismus, unilateral mydriasis and heterochromia are the presenting
clinical characteristics. Sixty percent of cases are nonhereditary and
unilateral, 15 percent are hereditary and unilateral and 25 percent are
hereditary and bilateral. There are few cases of monozygotic twins
with retinoblastoma. In the present study we analyzed monozygotic
twins with retinoblastoma in which only one of them was affected. DNA
from leukocytes was obtained with conventional methods. Monozygosity
was confirmed through GeneScan. Cytogenetic analysis was
performed with conventional methods. FISH analysis was done with
the cDNA LSI RB1 probe in leukocytes and oral cells of both twins and
their parents and in retinal tissue of affected twin. FISH analysis in 500
cells of affected twin showed: a) two copies of the RB1 gene in 20% of
retinal tissue and in 92% of leukocytes; b) one copy of the RB1 gene
in 56% of retinal tissue and in 8% of leukocytes and c) no copies of
the RB1 gene in 24% of retinal tissue. FISH analysis in leukocytes and
oral cells (500 cells) of both parents and the non-affected twin showed
no deletion of 13q14. We concluded that mutation in the twin with Rb
occurred in a post-zygotic event.
P07.10
Value of combined array cGH and conventional cytogenetic
analysis for a precise characterization of childhood and adult
solid tumors
E. Stejskalova 1 , H. Urbankova 2 , J. Malis 1 , K. Pycha 3 , L. Krskova 4 , R. Kodet 4 ,
M. Jarosova 5 ;
1 Department of Pediatric Hematology and Oncology, Prague, Czech Republic,
2 Department of Hemato-oncology, Olomouc, Czech Republic, 3 Department of
Pediatric Surgery, Prague, Czech Republic, 4 Institute of Pathology and Molecular
Medicine, Prague, Czech Republic, 5 Department of Hemato-oncology,
Olomouc, Czech Republic.
Genetic information has become important to pathologists for the differential
diagnosis of solid tumors. Chromosomal aberrations indicating
an unfavorable prognosis are of clinical value. Microarray Comparative
Genome Hybridisation (arrayCGH) allows for the detection of
copy number changes throughout the entire genome at a resolution
that far exceeds that of cytogenetics. ArrayCGH studies, especially of
pediatric solid tumors, are still scarce.
We have analysed 48 patients using array CGH, conventional cytogenetics
combined with FISH and, where possible, M-FISH. We have
correlated our findings with standard morphological histopathological
analysis and clinical features.
With this combined approach we have detected non random aberrations
involving 1q and 2q, +8, +20, a t(1;6)(q21;q26) and a
der(4)t(1;4)(q25;q34) characterising hepatoblastomas; 1q gain,
del(1p), monosomy 22, aberrations involving 16(q13-qter), i(7)(q10)
and a previously not published t(2;8)(p1.5;q22.3) in nefroblastomas
(Wilms) tumors. ArrayCGH has been useful in the detection of karyotype
abnormalities that were not detected by conventional cytogenetics,
some of them having prognostic impact. Samples that have failed
to grow in culture, for example osteosarcoma, or with a seemingly normal
karyotype, could be analysed by arrayCGH with valuable results.
Our findings bring further evidence regarding typical hepatoblastoma
abnormalities, so far scarcely reported, with array CGH analysis refining
the resolution of conventional cytogenetics. The detected changes
in the series of nefroblastoma patients support the already existing
evidence concerning prognostic significance of chromosomal aberrations
in this tumor. Array CGH analysis may broaden the spectrum of
detected changes and provide results even in negative or difficult to
grow in vitro samples.
P07.11
Analysis of cancer genes in histopathologically tumour-free
surgical margins in patients with oral squamous cell carcinoma
J. M. Milasin, D. Jelovac, M. Manasijevic, B. Nesic, B. Popovic, B. Ilic, V. Konstantinovic;
School of Dentistry, Belgrade, Serbia.
Oral cavity cancer is the sixth leading cancer worldwide and more
than 90% of malignant neoplasms of the oral cavity are squamous
cell carcinomas. 10-30% of patients with oral squamous cell carcinoma
(OSCC) develop local recurrences despite seemingly adequate
tumour resection and the incidence of metastasis is high. As p53, c-
Erb and c-Myc mutations have been considered as molecular changes
typical of cancer cells, their presence, if any, in histopathologically free
tumour margins, could be of great importance for the recurrence risk
evaluation. The aim of this study was to determine the incidence of
p53, c-Myc and c-Erb mutations in tumour margins, considered normal
from a histologic point of view. DNA was obtained from 40 mucosa
specimens, confirmed by a pathologist as free of neoplastic cells. P53
mutations were studied by PCR-SSCP, and sequencing, while differential
PCR was used for the detection of c-Myc and c-Erb B2 amplification.
A relatively high incidence of genetic lesions was detected: 11 out
of 40 patients (27.5%) harboured p53 mutations, 5 (12.5%) had c- Erb
B2, and 7 (17.5%) had c-Myc amplification. A close follow-up of these
patients is planned.
Local and distant spread has been a major challenge for a successful
cancer treatment. It is considered that verification of tumour-free
resection margins by conventional histopathological examination is
not sufficient. Molecular analysis of margins, targeting cancer genes,
could enable the selection of OSCC patients at higher risk for tumour
recurrence.