Genetic Determinants of Blood Cell Traits Influence Susceptibility to Childhood Acute Lymphoblastic Leukemia

ABSTRACT Acute lymphoblastic leukemia (ALL) is the most common childhood cancer. Despite overlap between genetic risk loci for ALL and hematologic traits, the etiological relevance of dysregulated blood cell homeostasis remains unclear. We investigated this question in a genome-wide association study (GWAS) of ALL (2666 cases, 60,272 controls) and multi-trait GWAS of 9 blood cell indices in the UK Biobank. We identified 3000 blood cell trait-associated ( P <5.0×10 −8 ) variants, explaining 4.0% to 23.9% of trait variation, and including 115 loci associated with blood cell ratios (LMR: lymphocyte/monocyte, NLR: neutrophil/lymphocyte, PLR: platelet/lymphocyte). ALL susceptibility was genetically correlated with lymphocyte counts ( r g =0.088, p=4.0×10 −4 ) and PLR ( r g = −0.072, p=0.0017). In Mendelian randomization analyses, genetically predicted increase in lymphocyte counts was associated with increased ALL risk (Odds ratio (OR)=1.16, p=0.031) and strengthened after accounting for other cell types (OR=1.48, p=8.8×10 −4 ). We observed positive associations with increasing LMR (OR=1.22, p=0.0017) and inverse effects for NLR (OR=0.67, p=3.1×10 −4 ) and PLR (OR=0.80, p=0.002). Our study shows that a genetically induced shift towards higher lymphocyte counts, overall and in relation to monocytes, neutrophils, and platelets, confers an increased susceptibility to childhood ALL.