PS1330 VARIABILITY IN THE EXTENT OF DEL(5Q) AND ITS CLINICAL IMPLICATION IN MYELODYSPLASTIC SYNDROMES (MDS)

Abstract

Background:The interstitial deletion of the long arm of chromosome 5—del(5q)—is the most common cytogenetic abnormality in MDS occurring either as a sole aberration or as a part of complex karyotypes (CK). MDS with isolated del(5q) are associated with a favorable outcome while MDS with CK relate to poor prognosis. Extent of deleted segment is highly variable. However, it remains unclear whether its size matters for the different MDS phenotypes.Aims:The aim was to compare the extent of deletion in 264 MDS patients [116 with isolated del(5q) and 148 with del(5q) involved in CK] and to assess the relationship of del(5q) extent and TP53 gene mutation.Methods:Extent of del(5q) was analyzed using I‐FISH (Abbott, MetaSystems), mBAND (MetaSystems) and array CGH/SNP (CytoChip Cancer SNP 180K, Illumina or SurePrint G3 Cancer CGH+SNP 4x180K, Agilent). CK were analyzed with mFISH (MetaSystems). Sequence analysis of TP53 gene was performed in 84 cases using amplicon deep sequencing (exons 4–11) on a 454 GS Junior system (Roche) or with TruSight Myeloid Panel Kit on MiSeq sequencing instruments (Illumina).Results:In the group with isolated del(5q), the most frequently deleted segment ranged between the bands 5q14 and 5q33.3, with the smallest deletion encompassing the 5q31.1–5q31.3 region (18.527 Mb). The TP53 mutation was proved in 19.4% cases. The size of the deletion did not significantly differ in patients with and without TP53 mutation. In the group with CK, the deletion often involved entire long arm including the telomeric region. In some cases, a part of short arm was also deleted, but we never observed the loss of the entire chromosome 5. The commonly conserved region (CCR) was localized in bands 5p12 to 5p14.1. In this group, the mutation of TP53 and/or LOH17p was detected in 49% of patients. The commonly deleted regions (CDR) were in the band 5q31.1 (5.522 Mb) in cases with isolated del(5q) and between the bands 5q31.1 and 5q31.3 (18.527 Mb) in patients with CK.Summary/Conclusion:Patients with isolated del(5q) had a smaller size of the deleted segment. More extensive 5q deletion was associated with higher karyotype complexity, increased frequency of TP53 aberrations and worse prognosis. Accurate analysis of breakpoints and range of del(5q) points out to the correlation of deletion size with increasing genomic instability in MDS and contributes to a better understanding of the MDS pathogenesis.Supported by RVO‐VFN64165, GACR P302/12/G157, ProgresQ28/LF1, MHCR 00023736.