Molecular and flow cytometric diagnostics for evaluation of therapy efficacy in myeloid leukemias

During the past decades, a lot of progress has been made in the treatment of acute and chronic myeloid leukemia. However, despite therapy, many patients experience relapse due to the presence of remaining leukemic cells, i.e. minimal residual disease (MRD). Our study contributed to the further identification of molecular MRD targets and showed that quantitative approaches (flow cytometry and molecular techniques) can be applied in routine clinical diagnostics to evaluate therapy efficacy and to guide therapeutic interventions in myeloid leukemia

High CD33-antigen loads in peripheral blood limit the efficacy of gemtuzumab ozogamicin |(Mylotarg®) treatment in acute myeloid leukemia patients

Gemtuzumab ozogamicin (Mylotarg®) induces remission in approximately 30% of relapsed AML patients. We previously demonstrated that gemtuzumab infusion results in near-complete CD33 saturation in peripheral blood, and that saturating gemtuzumab levels result in continuous binding and internalization of gemtuzumab due to renewed CD33 expression. We now demonstrate that a high CD33-antigen load in peripheral blood is an independent adverse prognostic factor, likely due to peripheral consumption of gemtuzumab. Indeed, CD33 saturation in bone marrow is significantly reduced (40-90% saturation) as compared with CD33 saturation in corresponding peripheral blood samples (>90%). In vitro, such reduced CD33 saturation levels were strongly related with reduced cell kill. Apparently, high CD33-antigen loads in blood consume gemtuzumab and thereby limit its penetration into bone marrow. Consequently, CD33 saturation in bone marrow is reduced, which hampers efficient cell kill. Therefore, gemtuzumab should be administered at higher or repeated doses, or, preferably, after reduction of the leukemic cell burden by classical chemotherapy

Homozygous DBF4 mutation as a cause for severe congenital neutropenia

Background Severe congenital neutropenia presents with recurrent infections early in life due to arrested granulopoiesis. Multiple genetic defects are known to block granulocyte differentiation, however a genetic cause remains unknown in approximately 40% of cases. Objective We aimed to characterize a patient with severe congenital neutropenia and syndromic features without a genetic diagnosis. METHODS: Whole exome sequencing results were validated using flow cytometry, Western blotting, co-immunoprecipitation, quantitative PCR, cell cycle and proliferation analysis of lymphocytes and fibroblasts and granulocytic differentiation of primary CD34+ and HL-60 cells. Results We identified a homozygous missense mutation in DBF4 in a patient with mild extra-uterine growth retardation, facial dysmorphism and severe congenital neutropenia. DBF4 is the regulatory subunit of the CDC7 kinase, together known as DBF4-dependent kinase (DDK), the complex essential for DNA replication initiation. The variant allele demonstrated impaired ability to bind CDC7, resulting in decreased DDK-mediated phosphorylation, defective S phase entry and progression and impaired differentiation of granulocytes associated with activation of the p53-p21 pathway. The introduction of WT DBF4 into patient CD34+ cells rescued the promyelocyte differentiation arrest. Conclusion Hypomorphic DBF4 mutation causes autosomal recessive severe congenital neutropenia with syndromic features

Immunophenotypic measurable residual disease (MRD) in acute myeloid leukemia: Is multicentric MRD assessment feasible?

Flow-cytometric detection of now termed measurable residual disease (MRD) in acute myeloid leukemia (AML) has proven to have an independent prognostic impact. In a previous multicenter study we developed protocols to accurately define leukemia-associated immunophenotypes (LAIPs) at diagnosis. It has, however, not been demonstrated whether the use of the defined LAIPs in the same multicenter setting results in a high concordance between centers in MRD assessment. In the present paper we evaluated whether interpretation of list-mode data (LMD) files, obtained from MRD assessment of previously determined LAIPs during and after treatment, could reliably be performed in a multicenter setting. The percentage of MRD positive cells was simultaneously determined in totally 173 LMD files from 77 AML patients by six participating centers. The quantitative concordance between the six participating centers was meanly 84%, with slight variation of 75%–89%. In addition our data showed that the type and number of LAIPs were of influence on the performance outcome. The highest concordance was observed for LAIPs with cross-lineage expression, followed by LAIPs with an asynchronous antigen expression. Our results imply that immunophenotypic MRD assessment in AML will only be feasible when fully standardized methods are used for reliable multicenter assessment

Flow cytometric immunobead assay for fast and easy detection of PML-RARA fusion proteins for the diagnosis of acute promyelocytic leukemia

The PML-RARA fusion protein is found in approximately 97% of patients with acute promyelocytic leukemia (APL). APL can be associated with life-threatening bleeding complications when undiagnosed and not treated expeditiously. The PML-RARA fusion protein arrests maturation of myeloid cells at the promyelocytic stage, leading to the accumulation of neoplastic promyelocytes. Complete remission can be obtained by treatment with all-trans-retinoic acid (ATRA) in combination with chemotherapy. Diagnosis of APL is based on the detection of t(15;17) by karyotyping, fluorescence in situ hybridization or PCR. These techniques are laborious and demand specialized laboratories. We developed a fast (performed within 4-5 h) and sensitive (detection of at least 10% malignant cells in normal background) flow cytometric immunobead assay for the detection of PML-RARA fusion proteins in cell lysates using a bead-bound anti-RARA capture antibody and a phycoerythrin-conjugated anti-PML detection antibody. Testing of 163 newly diagnosed patients (including 46 APL cases) with the PML-RARA immunobead assay showed full concordance with the PML-RARA PCR results. As the applied antibodies recognize outer domains of the fusion protein, the assay appeared to work independently of the PML gene break point region. Importantly, the assay can be used in parallel with routine immunophenotyping for fast and easy diagnosis of APL

A certified plasmid reference material for the standardisation of BCR-ABL1 mRNA quantification by real-time quantitative PCR

Serial quantification of BCR–ABL1 mRNA is an important therapeutic indicator in chronic myeloid leukaemia, but there is a substantial variation in results reported by diff

Malignant invasion of the cerebrospinal fluid in patients with a haematological malignancy: a single center retrospective study.

status: accepte

Performance evaluation of the Spinit® -BC, a new point-of-care assay for total WBC count with 5-part differential and hematocrit measurement

status: publishe

Analytical performance of an automated volumetric flow cytometer for quantitation of T, B and natural killer lymphocytes

BACKGROUND: Quantitation of lymphocyte subsets (B cells, T cells, CD4 and CD8 T cells and NK cells) classically relies on quantitation of lymphocytes and immunophenotyping by flow cytometry. AQUIOS CL (Beckman Coulter) is a fully automated system that performs an onboard volumetric cell count, automatically processes the sample (staining, lysing and fixation) and analyzes the results. We compared AQUIOS CL to a dual-platform analysis and evaluated analytical performance. METHODS: We evaluated precision, sample stability, inter-sample carryover, linearity and interpanel consistency. AQUIOS CL was compared to a dual-platform method (Sysmex XE-5000 and BD FACSCanto-II). A total of 113 patient samples were included: 45 from posttransplant patients, 44 from children and 24 random routine samples. The degree of automation was scored through the need of manual revisions triggered by AQUIOS CL run notifications and run flags. RESULTS: Intrarun and interrun variability was <9.1% with dedicated control material and <32.1% with patient samples. Relative values of lymphocyte subsets could be determined up to 48 h after venipuncture when the sample was kept at room temperature. There was no carryover and good linearity. Interpanel consistency was 3.3% for relative values and 9.4% for absolute values. Method comparison showed good analytical correlation between AQUIOS CL and a dual-platform method. Thirty-five percent of the samples triggered a run notification. In 74% of these samples, the results could be accepted without intervention, so in 26% of all samples, an unnecessary notification was generated. CONCLUSIONS: AQUIOS CL allows for reliable fully automated immunophenotyping of lymphocyte subset quantitation. Gating algorithms could be further improved.status: publishe