European Human Genetics Conference 2007 June 16 – 19, 2007 ...

Cancer genetics
to available biological markers values (ER, PR, Her2 status, lymph
nodes status, age, etc).
P0625. Identification of tumor-suppressor loci that may
contribute to the pathogenesis of uveal melanoma
I. K. Manokhina 1 , N. V. Sklyarova 2 , S. V. Saakyan 2 , D. V. Zaletaev 1 ;
1 Institute of Molecular Medicine, I.M. Sechenov Moscow Medical Academy,
Moscow, Russian Federation, 2 Helmholts Moscow Research Institute of Eye
Diseases, Moscow, Russian Federation.
Uveal melanoma (UM) is the most common primary intraocular neoplasm.
More than 50% of uveal melanomas are linked to large deletions
or monosomy of chromosome 3, but the specific genetic mechanisms
responsible for the malignant behavior of UM are still unknown.
OBJECTIVE: To identify tumor-suppressor loci that may contribute to
the pathogenesis of UM. METHODS: Loss of heterozygosity on chromosome
3 was investigated by PCR-based microsatellite analysis
in 45 tumors and related to clinical data. Microsatellite analysis was
performed using markers at 3p25.3, 3p21.3, 3p14.2, 3q26.3, 13q14,
9p21.2-p21.3, close to or within the VHL, RASSF1, FHIT, TRAIL, RB1,
CDKN2A loci. The methylation status of the VHL, RASSF1, FHIT, RB1,
CDKN2A promoter regions was analyzed using methyl-sensitive PCR.
RESULTS: In the majority of cases, LOH on chromosome 3 was detected
at all informative markers, indicating of monosomy 3 (20 of 45
tumors). RASSF1 promoter methylation was detected in 10 of the 45
(22%) patients with primary UM regardless of LOH status. No hypermethylation
of the VHL and FHIT promoter regions was found. Neither
LOH at RB1 locus, nor hypermethylation of the RB1 promoter region
was found. Methylation of the CDKN2A promoter and LOH in its locus
occured in some tumors. CONCLUSIONS: These data show that
monosomy 3 could be the most common event in UM development,
potentially of clinical relevance. LOH and promoter hypermethylation
of Rb1-pathway genes are rare events in UM. Further studies are necessary
to understand if the RASSF1 promoter methylation could have
a pathogenic effect in UM.
P0626. Inactivation of the VHL gene in sporadic clear cell renal
cancer
D. Mikhaylenko 1,2 , R. Kurynin 3 , A. Popov 4 , O. Karyakin 4 , M. Enikeev 3 , Y. Alyaev
3 , M. Nemtsova 1,2 , D. Zaletayev 1,2 ;
1 Research Centre for Medical Genetics RAMS, Moscow, Russian Federation,
2 Institute of Molecular Medicine at Sechenov Moscow Medical Academy,
Moscow, Russian Federation, 3 Clinic of Urology at Sechenov Moscow Medical
Academy, Moscow, Russian Federation, 4 Medical Radiological Research Center
RAMS, Obninsk, Russian Federation.
Renal cell carcinoma is the most common variant of the kidney cancer,
which accounts approximately 75% patients with this disease. The
majority of those tumors are characterized by inactivation of the VHL
gene suppressor as a result of mutations, allelic deletions and/or methylation.
We have conducted the complex molecular-genetic analysis
of 64 samples obtained from patients with the clear cell renal cancer.
VHL mutations were detected by SSCP and subsequent sequencing,
loss of heterozygosity was analyzed using STR-markers D3S1317
and D3S1038, methylation was tested by methylsensitive polymerase
chain reaction. All revealed variations were statistically analyzed
in respect to the parameters of primary tumors in various groups of
patients. Seventeen VHL somatic mutations were detected, 12 from
which were described for the first time. Allelic deletions of VHL were
found in 31.6%, and methylation - in 7.8% samples of the renal cancer.
As a whole, VHL inactivating events were presented in 46.9% cases
of disease, in 51.7% - among renal cancer patients with stage I. We
have not observed any association of mutations, loss of heterozygosity
and methylation with clinical-pathological parameters of disease.
Results of this investigation can be used in creation of a molecular
markers system of the renal cancer, for example, a methylation panel
of suppressor genes, they can be applied in investigation of properties
of various VHL mutations.
P0627. Molecular genetic testing in Von Hippel-Lindau
syndrome: limitations and implication for genetic counselling.
B. Quintáns 1 , M. Sobrido 2 , B. Graña 3 , F. Barros 2 , A. López-Soto 4 , M. Castro 5 , J.
Castro 2 , A. Carracedo 2 ;
1 Grupo de Medicina Xenómica-Hospital Clínico Universitario, Santiago de Compostela,
Spain, 2 Fundación Pública Galega de Medicina Xenómica, Santiago
de Compostela, Spain, 3 Servicio de Oncología-Hospital Clínico Universitario,
Santiago de Compostela, Spain, 4 Servicio de Medicina Interna-Hospital Comarcal
do Salnés, Vilagarcía de Arousa, Spain, 5 Servicio de Neurología-Complejo
Hospitalario de Pontevedra, Pontevedra, Spain.
Von Hippel-Lindau (VHL) is a dominantly inherited cancer syndrome
caused by mutations in the VHL tumour suppressor gene. Tumours
associated to VHL are haemangioblastomas of brain, spinal cord, and
retina, renal cell carcinoma, pheochromocytoma and endolymphatic
sac tumours. Manifestations and severity are highly variable within
and between families. Molecular genetic testing is indicated for at-risk
subjects in order to identify those deserving surveillance. We present
two kindreds with clinical diagnosis of VHL, molecular genetic testing
and counselling. Proband of FamS had bilateral renal carcinoma,
kidney and pancreatic cysts, a cerebellar syndrome since infancy
and neck-face dystonia, but no brain or spinal haemangioblastomas.
Family history: daughter (renal and pancreatic cysts), son (testicular
cysts), maternal aunt (metastasic tumour), and cousin (pheochromocytoma
age 30). A mutation not previously described in VHL was found
in the proband and both affected children: c.261_263delATGinsGCT
(W88L). A third, 9-year old child, tested negative for W88L. The mutation
was not present in her cousin. In FamV two individuals fulfilled
VHL criteria (brain and spinal cord haemangioblastomas, pancreatic
and renal cysts). No mutations were identified in VHL after sequencing
and dosage analysis by MLPA. Genetic counselling was requested for
a 28 year-old, asymptomatic sibling. None of the affected individuals
showed retinal angiomas, one of the cardinal features of VHL. These
families exemplify practical situations in which genetic counselling may
be hampered: 1) Novel mutations without proven pathogenicity, 2) Tumours
of the VHL spectrum in family members not co-segregating the
mutation (phenocopies) and 3) Failure to identify the causative mutation.
P0628. A frequent XPC mutation in xeroderma pigmentosum
patients from North Africa
N. Soufir1 , A. Sarasin2 , A. Bourillon1 , A. Stary2 , K. Khadir3 , B. Grandchamp1 , H.
Benchikhi3 ;
1 2 Hopital Bichat, APHP, Paris, France, Institut gustave Roussy, Villejuif, France,
3CHU Ibn Rochd, Casablanca, Morocco.
Introduction. Xeroderma pigmentosum (XP) is a rare autosomal recessive
disorder that is associated with a germline nucleotide excision repair
defect. Patients exhibit extreme sensitivity to sunlight and a 4000fold
increased frequency of skin cancers. Seven XP complementation
groups and a variant group have been identified, three of which are
believed to be more frequent (XPC, XPA, XPD-ERCC2).
Methods. We investigated the role of XPC, XPD and XPA genes in
eight unrelated consanguineous XP families from Maghreb (six from
Morocco, two from Tunisia). All index cases presented typical XP
symptoms including pronounced photosensitivity, multiple basal cell
carcinomas (80%), and malignant melanomas (20%). DNAs was extracted
after informed consent and initially subject to microsatellite
analysis by studying 2 microsatellites located in each three XP gene.
Homozygous patients were further analysed by sequencing the entire
gene coding sequence on a ABIPRISM 3130.
Results: A previously reported and recurrent homozygous nonsense
mutation in the XPA gene, R228X, was found in a patient from Tunisia.
Surprisingly, in the remaining seven unrelated families (87%), we identified
the same homozygous frameshift mutation, c.1643_1644delTG,
p.V548AfsX572. This mutation was previously reported in two other
unrelated families from Maghreb. XPC haplotype analysis highly suggested
a common fondator effect.
Conclusion. Our study suggests a predominant involvement of XPC
as a XP susceptibility gene in countries from North Africa. The high
frequency of the frameshift XPC mutation could, if confirmed, simplify
the molecular diagnosis of XP patients from Maghreb, and facilitate
prenatal diagnosis if requested by the families.
1