Family-based Association Study of Killer Cell Immunoglobulin-Like Receptor Genes with Leukemia

NK cell function is controlled by the cell expression of killer immunoglobulin-like receptors (KIRs) and their ligation with the corresponding HLA ligands. Various malignancies have been associated with certain KIRs surface cell expression and various KIR/HLA ligand combinations. Prior research using case/control study design demonstrates the role of KIR and KIR HLA ligands as genetic factor involved in tumor susceptibility. The objective of this study was to investigate the family-based association of KIRs, HLA class I ligands and KIR/ligand combinations with leukemia diagnosis in families having a leukemia diagnosed child. Sixty-seven families that met the index leukemia case criteria (acute lymphoblastic leukemia, ALL, n = 45; acute myeloid leukemia, AML, n = 13; chronic myeloid leukemia, CML, n = 9; first degree healthy relatives n = 159) were examined. Our study consisted of two phases. In Phase1 case-control study, we primarily compared patients to their healthy siblings to asses if a marker or genotype may be associated with leukemia, excluding the impact of the environment. Phase 2 consisted of a secondary family-based association study. KIR genotyping was performed by PCR-SSP method. KIR HLA ligands were defined by direct method using PCR-SSP method and/or indirect base on high resolution typing of HLA-A, -B, -C alleles. Results of phase 1 showed an increase in the frequency of KIR genotype (with a ratio = 0.57; higher frequency for inhibitory KIRs vs. activating KIRs) among leukemia patients compared to healthy siblings. Results of the phase 2 familial study observed an association between HLA-C1+/B^Bw4+/A^Bw4+ haplotype (a mediator of inhibitory signals) and leukemia. Also, we concluded that the absence of HLA-A^Bw4 alleles was related to leukemia development.