ABCB1 and acute lymphoblastic leukemia: However, when we performed the study on the combination of both SNPs (ABCB1 rs1045642+rs1128503), we observed that the rare allele combinations (TT+CT and TT+TT) were associated with a higher risk for ALL, which explains why children carrying such alleles are more likely to acquire the disease than those who have combinations with wild type genotypes.