XPD Lys751Gln Polymorphism and Etiology and Outcome of Childhood Acute Myeloid Leukemia.

Genetic polymorphism results in inter-individual variation in DNA repair capacity, and may in part account for susceptibility of a cell to genotoxic agents, and to malignancy. The DNA repair protein xeroderma pigmentosum complementation group D (XPD) is a major participant in the neucleotide excision repair pathway and is also involved in transcription initiation and in the control of cell cycle and apoptosis. Several studies have found associations between ineffective DNA repair and cancer risk. It is also thought that ineffective DNA repair may lead to additional genomic instability and tumors that are more aggressive. Several single nucleotide polymorphisms including an adenine to cytosine polymorphism leading to Lys751Gln in exon 23 of XPD have been shown to be associated with elevated frequency of chromosomal aberrations and variety of environmentally induced cancers in adults. We hypothesized that XPD polymorphism may play a role in causation of childhood AML. In addition, there are data that XPD polymorphism influences outcome of chemotherapy in adults with solid tumors. Therefore, we also evaluated its effect on outcome of AML therapy. Methods: 457 children treated for AML on CCG studies 2941 and 2961 (intensive induction with daunorubicin, idarubicin, Ara-C, 6-thioguanine, etoposide, dexamethasone, +/− fludarabine, Ara-C, idarubicin; consolidation with high-dose Ara-C and L-asparaginase or HLA-matched sibling BMT) were genotyped for XPD exon 23 polymorphism. Genotype frequencies were compared with published normal control frequencies. In addition, patient outcomes were analyzed according to genotype. Results: Comparison of gene frequencies in AML patients and reported normal controls showed similar frequencies (42.5% AA, 44.2% AC, 13.3% CC in patients vs. 44.2% AA, 45% AC, 10.8% CC in controls; p=0.54). There were no significant difference in OS (p=0.56), EFS (p=0.61), TRM (p=0.5) or relapse rate (p=0.88) between patients with 751AA genotype vs. 751AC/751CC genotypes, in contrast to reports in adult malignancies. Stratification of cases by age at diagnosis, white blood count at diagnosis, AML subtype, or cytogenetics revealed no difference in genotype frequencies. Conclusion: These data, representing the only data in pediatric AML, suggest that XPD genotype does not affect the etiology or outcome of childhood AML.