A standardized, sensitive and universal method for minimal residual disease (MRD) detection in acute myeloid leukemia (AML) is still pending. Although hyperexpression of Wilms' tumor (WT1) gene transcript has been frequently proposed as an MRD marker in AML, wide comparability of the various methods used for evaluating WT1 expression has not been given. We established and standardized a multicenter approach for quantifying WT1 expression by quantitative reverse transcriptase PCR (qRT-PCR), on the basis of a primer/probe set combination at exons 6 and 7. In a series of quality-control rounds, we analyzed 69 childhood AML samples and 47 normal bone marrow (BM) samples from 4 participating centers. Differences in the individual WT1 expressions levels ranged within o0.5 log of the mean in 82% of the cases. In AML samples, the median WT1/1E þ 04 Abelson (ABL) expression was 3.5E þ 03 compared with that of 2.3E þ 01 in healthy BM samples. As 11.5% of childhood AML samples in this cohort harbored WT1 mutations in exon 7, the effect of mutations on WT1 expression has been investigated, showing that mutated cases expressed significantly higher WT1 levels than wild-type cases. Hence, our approach showed high reproducibility and applicability, even in patients with WT1 mutations; therefore, it can be widely used for the quantitation of WT1 expression in future clinical trials.

Sequence polymorphisms (SPs) can serve as genetic markers for quantitative polymerase chain reactions (qPCR) for chimerism analysis, providing a significantly higher sensitivity compared to short tandem repeat PCR. In this study, a panel of 29 selected markers was evaluated in 317 patients with leukemia and myelodysplastic syndrome, who received allogeneic stem cell transplantation. In total, 5415 posttransplantation samples were analyzed. Recipient genotype discrimination was possible in 96% with a mean number of 2.5 (1-7) informative markers per recipient/donor pair. Marker specific standard dilution series from volunteers' DNA served as standard for quantification of chimerism. Sensitivity of the method was < or =1 x 10-3 (0.1% of recipient cells) in 83.3% of the assays. By this method, it was possible to very accurately detect autologous signals in the range from 0% to 0.5% (95% confidence interval [CI] +/-0.2), from 0.5% to 1% (95% CI +/-0.4), from 1% to 2% (95% CI +/-0.6) and from 2% to 5% (95% CI +/-1.2). Reproducibility of the quantified autologous signals was independent from the amount of DNA. This is the first report on a SP-based chimerism system allowing for the performance of chimerism analyses for virtually all patients with high sensitivity, excellent reproducibility, and precision of measurement.

Enrichment of cell subpopulations is a prerequisite for lineage-specific chimerism analysis (LCA), a frequent approach in follow-up after allo-SCT. An efficient enrichment technique is Magnetic Cell Sorting (MACS) using the AutoMACS separator. However, evaluation of purity, recovery and applicability for PCR-based chimerism analysis of MACS-enriched subpopulations from post-transplant peripheral blood, providing reduced cell numbers and/or unbalanced proportions of subpopulations, is currently unavailable. We performed enrichment of CD3-, CD14-, CD15-, CD19-and CD56-positive subpopulations using 'Whole Blood MicroBeads' and AutoMACS separator in 137 prospectively collected peripheral blood samples from 15 paediatric patients after allo-CD3-/CD19-depleted SCT. Purity was assessed by immune phenotyping. Recovery and applicability for chimerism analysis was evaluated. Excellent purity 490% was achieved in CD14-, CD15-positive cells in 81%, 95% of the isolates and in 86% of CD3 and CD19 isolates, if ACC was 4400 cells per ll. Median purity of CD56-positive isolates was 78.9%. Recovery 490% was between 93 (CD56) and 37% (CD15). Conventional and real-time PCR-based chimerism analysis was feasible in virtually all samples. Isolation of cell subpopulations by automated cell enrichment in post-transplant peripheral blood is feasible and fast providing excellent purity and recovery for routine lineage-specific chimerism analysis.

Malformations of limb elements produced in C57BL/10 mice by various dosages of 5-fluoro-2'-deoxycytidine given at day IX or XI were analyzed. This investigation was restricted to the analysis of aplasia, synostosis, synchondrosis, and inhibition of calcification. Teratological patterns were described in detail. Day-IX treatment induced patterns of ulnar, radial, ulnarradial, and tibia1 aplasias. Day-XI treatment produced groups of defects with common characteristics, but no clear teratological patterns. Synostoses, synchondroses, and inhibition of calcification predominated. Dose-response relations occurred after treatment at both stages.