Myelodysplastic Syndromes with 20q Deletion: Incidence, Prognostic Value and Impact on Response to Azacitidine of ASXL1 Chromosomal Deletion and Genetic Mutations

Introduction: The 20q deletion [del(20q)] is a recurrent chromosomal aberration in myelodysplastic syndromes (MDS) and, as a single abnormality, is associated according to the Revised International Prognostic Scoring System (IPSS-R) with a favorable outcome. However, the breakpoint of del(20q) is very heterogeneous and may cause deletion of the ASXL1 gene (20q11.21). This gene is an important epigenetic regulator of hematopoiesis and its mutations have been associated in MDS with a shorter overall survival (OS) and a lower response to azacitidine (AZA). Aim: To assess the incidence, prognostic value and impact on response to AZA of ASXL1 chromosomal alterations and genetic mutations in MDS patients with del(20q). Methods: We studied 153 patients diagnosed with MDS and del(20q) as a sole abnormality (n=93), with an additional chromosomal abnormality (n=27) or in a complex karyotype (n=33). Response to AZA therapy was assessed using the 2006 International Working Group (IWG) criteria. Analysis of ASXL1 chromosome alterations was performed by FISH (Empire Genomics probe). Samples with ASXL1 alterations by FISH were analyzed using the Agilent SurePrint G3 Human CGH 8x60K Microarray. Mutations of ASXL1 were detected by Sanger sequencing. SF3B1, SRSF2, U2AF1, DNMT3A, IDH1, IDH2, TP53, RUNX1, and SETBP1 mutations were screened by high-resolution melting and positives were confirmed by Sanger sequencing. An in vitro assay of the response to AZA in HAP1 and HAP1 ASXL1 knockout cell lines (Horizon) was also performed. The association of the clinical characteristics with the molecular findings was analyzed with the SPSS statistical program (v.20.0) and P values