Monoallelic and biallelic deletions of 13q14 in a group of CLL/SLL patients investigated by CGH Haematological Cancer and SNP array (8x60K)

Beata Grygalewicz, Renata Woroniecka, Jolanta Rygier, Klaudia Borkowska, Iwona Rzepecka, Martyna Łukasik, Agnieszka Budziłowska, Grzegorz Rymkiewicz, Katarzyna Błachnio, Beata Nowakowska, Magdalena Bartnik, Monika Gos, Barbara Pieńkowska-Grela

Deletion of 13q14 is the most common cytogenetic change in chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) and is detected in about 50 % of patients by fluorescence in situ hybridization (FISH), which can reveal presence of del(13)(q14) and mono- or biallelic deletion status without information about the size of the lost region. Array-comparative genomic hybridization (aCGH) and single nucleotide polymorphism (SNP) can detect submicroscopic copy number changes, loss of heterozygosity (LOH) and uniparental disomy (UPD) regions. The purpose of this study was detection of the size of del(13)(q14) deletion in our group of patients, comparing the size of the monoallelic and biallelic deletions, detection of LOH and UPD regions. We have investigated 40 CLL/SLL patients by karyotype, FISH and CGH and SNP array. Mutational status was of immunoglobulin heavy-chain variable-region (IGVH) was also examined. The size of deletion ranged from 348,12 Kb to 38.97 Mb. Detected minimal deleted region comprised genes: TRIM13, miR-3613, KCNRG, DLEU2, miR-16-1, miR-15a, DLEU1. The RB1 deletions were detected in 41 % of cases. The average size in monoallelic 13q14 deletion group was 7,2 Mb while in biallelic group was 4,8 Mb. In two cases 13q14 deletions were located in the bigger UPD regions. Our results indicate that bigger deletion including RB1 or presence of biallelic 13q14 deletion is not sufficient to be considered as adverse prognostic factor in CLL/SLL. CytoSure Haematological Cancer and SNP array (8x60k) can precisely detect recurrent copy number changes with known prognostic significance in CLL/SLL as well as other chromosomal imbalances. The big advantage of this array is simultaneous detection of LOH and UPD regions during the same test.