PB1700 LOSS OF CHROMOSOME 9 AND/OR 1 HETEROZYGOSITY IN TUMOR CELLS GENOME COME UP WITH ABO AND/OR RH CHANGE IN RELAPSED AML BUT NOT ALL PATIENTS.
Authors: N. Risinskaya, V. Vasilyeva, A. Yushkova, A. Sudarikov, L. Golovkina, A. Stremouchova, T. Pushkina, V. Surin, O. Pshenichnikova, L. Kuzmina, E. Parovichnikova, V. Savchenko
Journal: HemaSphere (2019)

Background: The rare phenomenon of splitting or alteration of ABO and/or RHD and RHCE phenotypes in the onset of the disease or in relapse, observed in a number of myeloproliferative, but not lymphoproliferative diseases, is probably caused by a loss of heterozygosity in blast cell genome. Aims: To correlate ABO, RHD, RHCE genotype and phenotype changes in remission and relapse with possible loss of heterozygosity in the regions 9q34.2 and 1p36.11 in AML and ALL patients. Methods: Study includes 62 patients that received allogeneic BMT in the National Research Center for Hematology, Moscow, between 2012 and 2018. Chimerism after BMT and loss of heterozygosity (LOH) in tumor cells genomes was evaluated by STR analysis with COrDIS Plus multiplex PCR kit for amplification of 19 polymorphic STR‐markers and amelogenin loci. The fragment analysis was performed on a 3130 Genetic Analyzer (Applied Biosystems, USA). Informative loci were chosen by comparison of pretransplant patient's and donor's DNAs. The percentage of donor chimerism was calculated using standard formula. High‐resolution chromosomal microarray (CMA) was performed using Affimetrix CytoscanTM HD array platform to verify the loss of heterozygosity. Data processing was carried out using Chromosome Analysis Suite v.4.0 software, genome assembly version hg19, GRCh37 Genome Reference Consortium Human Reference 37, https://genome.ucsc.edu/ . The ABO and Rh phenotypes of RBC in posttransplant non‐transfused patients were detected by hemagglutination methods in plate and tube using monoclonal antibodies to ABO and Rhesus antigens (Hematolog, Russia). The ABO and Rh genotypes were evaluated by ABO‐Type and RH‐Type PCR‐SSP kits (BAG, Germany) and confirmed by direct Sanger sequencing. Results: Four patients (2 AML patients, 1 B‐ALL and 1 T‐ALL patient) from 17 LOH‐positive patients had LOH in 9 and/or 1 chromosomes (Table 1). Patient#1 with AML and heterozygous ABO∗B1O1 and homozygous RH∗D‐, RHCE∗ccee genotype received transplant from ABO∗A1O1 and RH∗D+, RHCE∗C w CDee donor. For this patient the LOH in 9q31.1‐34.3 area of 9 chromosome and heterozygous ABO∗B1O1 genotype were established in blast cells in relapse. The O (I) Rh‐ ccdee phenotype of RBC was detected on +127 day after BMT, when the patient was in relapse, because of transfused O erythrocytes. In patient#2 with AML without relapse the loss of 9 chromosome was established cytogenetically in the onset of disease. The ABO∗A 1 B 1 and RH∗ CcDEe genotype was shown for this patient and ABO∗A2O1 RH∗CcDee for donor. Day +30 after BMT the ABO phenotype splitting in RBC was found: 90% of A1B (IV) Rh+ CcDEe and 10% of A1(II)Rh+ CcDee. The loss of 1p36.3‐1p35.3, 1p34.3‐1p32.3 and uniparental disomy of 9 chromosome was detected in tumor cells of patient#3 with T‐ALL. While patient had ABO∗O 1 O 1 RH∗C w cDEe genotype and donor was ABO∗B1O1 RH∗CcDee , homozygous genotype ABO∗O 1 O 1 RH∗C w C w Dee was detected on +160day after BMT, when the patient had relapse of disease. However RBC phenotype was B(III) CcDee fully compliant with donor's genotype. Patient#4 with B‐ALL had uniparental disomy of 1 and 9 chromosomes in tumor cells. Since patients phenotype was B(III) CCDee and donors – B(III) CcDee the allele loss in this case may not result into phenotype change. Summary/Conclusion: The data obtained confirms the impact of LOH on ABO and Rh phenotype splitting or alteration in onset or disease relapse of AML but not ALL. More research of extended samples of AML and ALL patients is required to confirm reported observations. image