Detection of BCR-ABL fusion proteins in patients with leukemia using a cytometric bead array

Multiparametric Flow Cytometry for MRD Monitoring in Hematologic Malignancies: Clinical Applications and New Challenges

Simple Summary

In hematologic cancers, Minimal Residual Disease (MRD) monitoring, using either molecular (PCR) or immunophenotypic (MFC) diagnostics, allows the identification of rare cancer cells, readily detectable either in the bone marrow or in the peripheral blood at very low levels, far below the limit of classic microscopy. In this paper, we outlined the state-of-the-art of MFC-based MRD detection in different hematologic settings, highlighting main recommendations and new challenges for using such method in patients with acute leukemias or chronic hematologic neoplasms. The combination of new molecular technologies with advanced flow cytometry is progressively allowing clinicians to design a personalized therapeutic path, proportionate to the biological aggressiveness of the disease, in particular by using novel immunotherapies, in view of a modern decision-making process, based on precision medicine.

Abstract

Along with the evolution of immunophenotypic and molecular diagnostics, the assessment of Minimal Residual Disease (MRD) has progressively become a keystone in the clinical management of hematologic malignancies, enabling valuable post-therapy risk stratifications and guiding risk-adapted therapeutic approaches. However, specific prognostic values of MRD in different hematological settings, as well as its appropriate clinical uses (basically, when to measure it and how to deal with different MRD levels), still need further investigations, aiming to improve standardization and harmonization of MRD monitoring protocols and MRD-driven therapeutic strategies. Currently, MRD measurement in hematological neoplasms with bone marrow involvement is based on advanced highly sensitive methods, able to detect either specific genetic abnormalities (by PCR-based techniques and next-generation sequencing) or tumor-associated immunophenotypic profiles (by multiparametric flow cytometry, MFC). In this review, we focus on the growing clinical role for MFC-MRD diagnostics in hematological malignancies—from acute myeloid and lymphoblastic leukemias (AML, B-ALL and T-ALL) to chronic lymphocytic leukemia (CLL) and multiple myeloma (MM)—providing a comparative overview on technical aspects, clinical implications, advantages and pitfalls of MFC-MRD monitoring in different clinical settings.

Non-infectious outer membrane vesicles derived from Brucella abortus S19Δper as an alternative acellular vaccine protects mice against virulent challenge

The prime human and animal safety issues accentuate the search of promising newer alternative vaccine candidates to resolve complications associated with the live attenuated Brucella abortus strain19 (S19) vaccine. Outer membrane vesicles (OMVs S19 Δper) extracted from Brucella abortus S19Δper (S19Δper) as an alternative subunit vaccine candidate has been explored in the present study as OMVs are endowed with immunogenic molecules, including LPS and outer membrane proteins (OMPs) and do not cause infection by virtue of being an acellular entity. The LPS defective S19Δper released a higher amount of OMVs than its parent strain S19. Under transmission electron microscopy (TEM), OMVs were seen as nano-sized outward bulge from the surface of Brucella. Dynamic light scattering analysis of OMVs revealed that OMVs S19Δper showed the less polydispersity index (PDI) than OMVs S19 pointing towards relatively more homogenous OMVs populations. Both OMVs S19Δper and OMVs S19 with or without booster dose and S19 vaccine were used for immunization of mice and subsequently challenged with 2 × 10⁵ CFU virulent Brucella abortus strain 544 (S544) to assess protective efficacy of vaccines. The less splenic weight index and less S544 count in OMVs immunized mice in comparison to unimmunized mice after S544 challenge clearly indicated good protective efficacy of OMVs. OMVs S19 Δper induced relatively high titer of IgG than OMVs S19 but conferred nearly equal protection against brucellosis. An ELISA based determination of IgG and its isotype response, Cytometric Bead Array (CBA) based quantitation of serum cytokines and FACS based enumeration of CD4⁺ and CD8⁺ T cells revealed high titer of IgG, production of both Th1 (IgG2a) and Th2 (IgG1) related antibodies, stimulation of IL-2, TNF (Th1) and IL-4, IL-6, IL-10 (Th2) cytokines, and induced T cell response suggested that OMVs S19Δper elicited Th1 and Th2 type immune response and ensured protection against S544 challenge in murine model.

Monitoring of Minimal Residual Disease (MRD) in Chronic Myeloid Leukemia: Recent Advances

Chronic myeloid leukemia (CML) is a myeloproliferative neoplasm caused by the BCR-ABL1 fusion gene generation as a consequence of the t(9;22)(q34;q11) rearrangement. The identification of the BCR-ABL1 transcript was of critical importance for both CML diagnosis and minimal residual disease (MRD) monitoring. In this review, we report the recent advances in the CML MRD monitoring based on RNA, DNA and protein analysis. The detection of the BCR-ABL1 transcript by the quantitative reverse-transcriptase polymerase chain reaction is the gold standard method, but other systems based on digital PCR or on GeneXpert technology have been developed. In the last years, DNA-based assays showed high sensitivity and specificity, and flow cytometric approaches for the detection of the BCR-ABL1 fusion protein have also been tested. Recently, new MRD monitoring systems based on the detection of molecular markers other than the BCR-ABL1 fusion were proposed. These approaches, such as the identification of CD26+ leukemic stem cells, microRNAs and mitochondrial DNA mutations, just remain preliminary and need to be implemented. In the precision medicine era, the constant improvement of the CML MRD monitoring practice could allow clinicians to choose the best therapeutic algorithm and a more accurate selection of CML patients eligible for the tyrosine kinase inhibitors discontinuation.

Evaluation of a new flow cytometry based method for detection of BCR-ABL1 fusion protein in chronic myeloid leukemia

Background

Philadelphia chromosome, a hallmark of chronic myeloid leukemia (CML), plays a key role in disease pathogenesis. It reflects a balanced reciprocal translocation between long arms of chromosomes 9 and 22 involving BCR and ABL1 genes, respectively. An accurate and reliable detection of BCR-ABL fusion gene is necessary for the diagnosis and monitoring of CML. Previously, many technologies, most of which are laborious and time consuming, have been developed to detect BCR-ABL chimeric gene or chromosome.

Methods

A new flow cytometric immunobead assay was used for detection of BCR-ABL fusion proteins and applicability, sensitivity, reliability, efficacy and rapidity of this method was evaluated.

Results

From February 2009 to January 2014, a total 648 CML patients were investigated for the status of BCR-ABL1 protein. Among them, 83 patients were enrolled for comparative study of BCR-ABL1 positivity by three routinely used procedures like karyotyping, and quantitative real time PCR (RT-PCR) as well as immunobead flow cytometry assay. BCR-ABL protein analysis was found consistent, more sensitive (17% greater sensitivity) and reliable than the conventional cytogenetics, as flow cytometry showed 95% concordance rate to RT-PCR.

Conclusion

BCR-ABL fusion protein assay using a new flow cytometric immunobead might be useful in the diagnosis and monitoring CML patients.

Reconsideration of BCR-ABL protein flow cytometric immunobead assay: how potent to diagnose and monitor chronic myeloid leukemia?

INTRODUCTION

Chronic myeloid leukemia (CML) is typically associated with the Philadelphia chromosome, resulting in the production of BCR-ABL fusion oncoprotein with upregulated tyrosine kinase activity. We aimed to evaluate a new flow cytometric immunobead assay to detect BCR-ABL protein in a group of patients with CML.

METHODS

We enrolled 49 patients with CML, whose qRT-PCR and/or cytogenetic analysis of Philadelphia chromosome aberration was available, including tyrosine kinase inhibitors (TKIs)-naïve and (TKIs)-treated patients with various levels of response. Twenty Philadelphia-negative healthy individuals were also enrolled to obtain analytical negative controls. Peripheral blood samples were analyzed for BCR-ABL fusion protein by flow cytometry.

RESULTS

The BCR-ABL fusion protein flow cytometric assay seemed efficacious to both diagnose the presence (P-value <0.0001) and distinguish the levels (P-value = 0) of the Philadelphia chromosome aberration. Groups of TKI-naïve and TKI-treated patients as well as levels of molecular/cytogenetic response to TKI-therapy were effectively discriminated (P-value <0.01). The receiver operating characteristic (ROC) curve analysis indicated the diagnostic value of the assay as excellent (AUC = 0.95, P-value = 0).

CONCLUSIONS

The evaluated BCR-ABL fusion protein assay might be useful for diagnosing and monitoring Philadelphia chromosome aberration.

Aberrant production of Th1/Th2/Th17-related cytokines in serum of C57BL/6 mice after short-term formaldehyde exposure

Previous studies have shown that formaldehyde (FA) could cause immunotoxicity by changing the number of T lymphocytes and that cytokines play a pivotal role in the regulation of T lymphocytes. However, the previously used cytokine detection methods are difficult to use in the measurement of several cytokines in a small amount of sample for one test. Therefore, the cytometric bead array (CBA) technique was used. CBA showed better analytical efficiency and sensitivity than the previous methods. C57BL/6 mice were exposed to the control (normal saline), low FA concentration (0.5 mg/kg), and high FA concentration (2 mg/kg) for 1 week or 1 month. The contents of cytokines, including Th1-related cytokines (IL-2, IFN-γ, and tumor necrosis factor), Th2-related cytokines (IL-4, IL-6, and IL-10), and Th17-related cytokines (IL-17A), were measured by using the BD FACS Canto II Flow Cytometer and analyzed by FCAP ArrayTM Software. Th1/Th2/Th17-related cytokines showed a slightly decreasing trend after low FA exposure. Conversely, a significantly increasing trend was found after high FA exposure. Th1/Th2/Th17-related cytokines all serve important functions in the immune reactions in mice after FA exposure.