Presence of heterozygous ATM deletion may not be critical in the primary response of chronic lymphocytic leukemia cells to fludarabine.

OBJECTIVES: Abnormalities of the TP53 or ATM, cooperating tumor-suppressor genes, significantly worsen the treatment options for chronic lymphocytic leukemia (CLL) patients. Although the aberrations seem to be mutually exclusive in this leukemia, inactivation of the former gene leads to worse prognosis. We tested the in vitro sensitivity of the CLL samples with heterozygous ATM deletion to fludarabine and combination of fludarabine and rituximab; the responses were compared with the TP53-abnormal and wild-type (wt) cells to delimitate relative significance of ATM deletion. METHODS: In vitro analysis was performed on fifty-nine characterized CLL samples using viability assay WST-1. Western blot and real-time RT-PCR were used to monitor the activation of the ATM/p53 pathway. RESULTS AND CONCLUSIONS: At the clinically relevant concentration of fludarabine, TP53-abnormal samples exhibited markedly higher resistance to fludarabine than the remaining CLL samples (P = 0.012); cohort with ATM deletion was not more resistant than wt cells. A similar induction of the p53 protein and its downstream target genes PUMA and BAX in ATM-deleted and wt cells confirmed that the former subgroup has preserved a critical pro-apoptotic response. Proportions of the samples, which had been sensitized to fludarabine by rituximab pretreatment, were insignificantly lower (P = 0.22) in the TP53-abnormal and ATM-deleted subgroups compared to the wt cases (30%; 29%; 50%, respectively). The presence of ATM (11q22-23) deletion in the CLL cells should not be considered an indication of resistance to fludarabine or its combination with rituximab.

Cost-effective genotyping of human MBL2 gene mutations using multiplex PCR.

Mannose-binding lectin (MBL) deficiency is associated with increased susceptibility to various infections and autoimmune disorders. It is caused by certain polymorphisms in the MBL2 gene promoter and mutations in the coding region of the gene. In this report, we present a novel, rapid, efficient and cost-effective method of two multiplex polymerase chain reactions (PCRs) for the assessment of three structural point mutations within exon 1 at codons 52, 54 and 57. Three additional PCR reactions for the detection of promoter polymorphisms at positions -550 and -221 were performed. MBL2 haplotypes in 359 individuals of the general Czech population were detected using this approach. The rare LYD haplotype was found in 1.1% of all alleles.