PB1711 MUTATIONAL ANALYSIS WILMS TUMOR 1 GENE IN DE NOVO CASES OF ACUTE MYELOID LEUKAEMIA; PREVALENCE, CORRELATION AND REPORT OF NOVEL MUTATION IN INDIAN POPULATION
Authors: Kumar C. , haider I. , Jain G. , Tanwar P. , Bakhshi S. , Kumar L. 
Published: June 2019

Background:

Cytogenetic and molecular abnormalities associated with pathogenesis of acute myeloid leukemia (AML) are broad and heterogeneous and acts as a cardinal marker for AML classification, prognostication and risk stratification. Mutation of the Wilms tumour 1 gene (WT1) is relatively frequent in leukemia and has been found to be present in about 10% > 15% of cases of AML mainly affecting exons 7 and 9, and less frequently exons 1, 2, 3, and 8. Different studies show variable and conflicting results with few showing poor prognosis in cases of AML due to WT1 overexpression or mutation, while others suggesting that WT1 has no significant impact on the prognosis of AML.

Aims:

The objective of this pilot study was to evaluate the prevalence of WT1 gene mutation in de novo cases of AML and its correlation with clinical features and prognosis.

Methods:

Study was conducted at All India Institute of Medical Sciences, New Delhi in 100 de novo cases of AML across the all age groups. Bone marrow aspirates (BMA) or peripheral blood (PB) sample was collected from diagnosed cases of AML and were processed for genomic DNA extraction. Genomic DNA amplified by polymerase chain reaction (PCR) for targeted regions exon 7 and 9 of WT1 gene using designed primer pair (forward and reverse for both exon 7 and 9). The PCR amplified product was then subjected to direct Sanger sequencing using genetic analyzer 3100/3700 (Applied bio‐system, USA). The targeted gene sequence results were then analyzed using Chromas© 2.6 software tool. The statistical analysis of data was done using Pearson's chi‐squared test (χ2) and Fisher's exact test.

Results:

1. The WT1 point mutation (substitution) was identified in two cases (2%) aged 15 and 28 years respectively on exon 9 of WT1 gene. One of these two mutations was novel and has not been previously reported.

2. Twelve cases (12%) were found to have synonymous single nucleotide polymorphism (SNP) in exon 7 which has been previously reported in SNP database (rs16754) as heterozygous in nature (WT1 A→G).

3. Blast percentage was >50% in both the cases harbouring WT1 mutation (mutant cases). However, there were no statistically significant differences in other clinical and haematological parameters like haemoglobin, white blood cells (WBCs) count and platelets counts between wild type and mutant cases.

4. Both mutant cases were young adults, relapsed after consolidation and eventually met early death compared to wild type cases.

Summary/Conclusion:

Only few case studies on WT1 gene mutation in AML have been reported and there is lack of such study and precise published data from India to date. From this pilot study we conclude that WT1 mutation is not so prevalent among de novo cases of AML in Indian population. Correlation between WT1 mutation and clinical outcome of the cases suggested that mutant cases had poor clinical outcome and early death. However, this study was limited by a relatively small sample size and incorporating only the mutational hotspot region of the gene. In future we need to perform this study on larger sample size together with study of whole WT1 gene by next generation sequencing (NGS) in order to reach any statistically significant conclusion.