Immunophenotypic Modulation of the Blast Cells in Childhood Acute Lymphoblastic Leukemia Minimal Residual Disease Detection

A concise review of flow cytometric methods for minimal residual disease assessment in childhood B-cell precursor acute lymphoblastic leukemia

Minimal residual disease refers to a leukemia cell population that is resistant to chemotherapy or radiotherapy and leads to disease relapse. The assessment of MRD is crucial for making an accurate prognosis of the disease and for the choice of optimal treatment strategy. Here, we review the advantages and disadvantages of the available genetic and phenotypic methods and focus on the multiparametric flow cytometry as a promising method with greater sensitivity, speed, and standardization options. In addition, we discuss how the application of automated data analysis outweighs the use of complex combinations of windows and gates in classical analysis, thus eliminating subjective evaluation.

Immunophenotype of Measurable Residual Blast Cells as an Additional Prognostic Factor in Adults with B-Cell Acute Lymphoblastic Leukemia

Measurable residual disease (MRD) is a well-known independent prognostic factor in acute leukemias, and multicolor flow cytometry (MFC) is widely used to detect MRD. MFC is able not only to enumerate MRD accurately but also to describe an antigen expression profile of residual blast cells. However, the relationship between MRD immunophenotype and patient survival probability has not yet been studied. We determined the prognostic impact of MRD immunophenotype in adults with B-cell acute lymphoblastic leukemia (B-ALL). In a multicenter study RALL-2016 (NCT03462095), 267 patients were enrolled from 2016 to 2022. MRD was assessed at the end of induction (day 70) in 94 patients with B-ALL by six- or 10-color flow cytometry in the bone marrow specimens. The 4 year relapse-free survival (RFS) was lower in MRD-positive B-ALL patients [37% vs. 78% (p < 0.0001)]. The absence of CD10, positive expression of CD38, and high expression of CD58 on MRD cells worsened the 4 year RFS [19% vs. 51% (p = 0.004), 0% vs. 51% (p < 0.0001), and 21% vs. 40% (p = 0.02), respectively]. The MRD immunophenotype is associated with RFS and could be an additional prognostic factor for B-ALL patients.

Go with the Flow—Early Assessment of Measurable Residual Disease in Children with Acute Lymphoblastic Leukemia Treated According to ALL IC-BFM2009

Simple Summary

Monitoring of residual disease is a very important aspect of modern treatment approaches in many types of cancer. In acute leukemias in both children and adults, molecular and cytometric methods are used to assess the burden of leukemia at different points during therapy. Residual disease measured at the end of induction was shown to be the strongest predictor of outcome. Analyzing the outcomes of children with acute lymphoblastic leukemia (ALL), we aimed to establish the most informative cut-off and time point of assessment. Applying only the measurement of residual disease by flow cytometry along with genotypic findings, we managed to identify patients with a poor prognosis. Although new precise, molecular techniques as the next generation sequencing strategy are approaching daily clinical practice, flow cytometry is still a reliable, standardized method of residual disease detection. We may say ‘go with the flow’; thus, the assessment of residual disease by multiparametric flow cytometry is a proper method for the management of ALL patients according to risk-adapted therapies.

Abstract

Measurable residual disease (MRD) is a well-known tool for the evaluation of the early response to treatment in patients with acute lymphoblastic leukemia (ALL). In respect to predicting the relapse the most informative cut-off and time point of MRD measurement during therapy were evaluated in our study. Between 1 January 2013 and 31 December 2019, multiparametric flow cytometry (MFC) MRD was measured in the bone marrow of 140 children with ALL treated according to the ALL IC-BFM2009 protocol. The MRD cut-off of 0.1% and day 33, end of induction, were the most discriminatory for all patients. Patients with negative MRD on day 15 and 33 had a higher 5-year overall survival—OS (100%) and a higher relapse-free survival—RFS rate (97.6%) than those with positive levels of MRD (≥0.01%) at both time points (77.8% and 55.6%, p = 0.002 and 0.001, respectively). Most patients with residual disease below 0.1% on day 15 exhibit hyperdiploidy or ETV6-RUNX1 in ALL cells. Measurement of MRD at early time points can be used with simplified genetic analysis to better identify low and high-risk patients, allowing personalized therapies and further improvement in outcomes in pediatric ALL.

Critical evaluation of the utility of pre- and post-therapy immunophenotypes in assessment of measurable residual disease in B-ALL

Measurable residual disease (MRD) is an important parameter to predict outcome in B-cell acute lymphoblastic leukemia (B-ALL). Two different approaches have been used for the assessment of MRD by multiparametric flow cytometry that include the "Leukemia Associated Aberrant Immunophenotype (LAIP)" and "Difference from Normal (DFN)" approach. In this retrospective study, we analyzed 539 samples obtained from 281 patients of which 258 were paired samples and the remaining 23 samples were from post-induction time point only, to explore the utility of baseline immunophenotype (IPT) for MRD assessment. Single-tube 10-color panel was used both at diagnosis and MRD time points. Out of 281 patients, 31.67% (n = 89) were positive and 68.32% (n = 192) were negative for MRD. Among 258 paired diagnostic and follow-up samples, baseline IPT was required in only 9.31% (24/258) cases which included cases with hematogone pattern and isolated dim to negative CD10 expression patterns. Comparison of baseline IPT with post-induction MRD positive samples showed a change in expression of at least one antigen in 94.04% cases. Although the immunophenotypic change in expression of various antigens is frequent in post-induction samples of B-ALL, it does not adversely impact the MRD assessment. In conclusion, the baseline IPT is required in less than 10% of B-ALL, specifically those with hematogone pattern and/or dim to negative expression of CD10. Hence, a combination of DFN and LAIP approach is recommended for reliable MRD assessment.

Immunophenotypic shift in the B-cell precursors from regenerating bone marrow samples: A critical consideration for measurable residual disease assessment in B-lymphoblastic leukemia

Accurate knowledge of expression patterns/levels of commonly used MRD markers in regenerative normal-B-cell-precursors (BCP) is highly desirable to distinguish leukemic-blasts from regenerative-BCP for multicolor flow cytometry (MFC)-based measurable residual disease (MRD) assessment in B-lymphoblastic leukemia (B-ALL). However, the data highlighting therapy-related immunophenotypic-shift in regenerative-BCPs is scarce and limited to small cohort. Herein, we report the in-depth evaluation of immunophenotypic shift in regenerative-BCPs from a large cohort of BALL-MRD samples. Ten-color MFC-MRD analysis was performed in pediatric-BALL at the end-of-induction (EOI), end-of-consolidation (EOC), and subsequent-follow-up (SFU) time-points. We studied normalized-mean fluorescent intensity (nMFI) and coefficient-of-variation of immunofluorescence (CVIF) of CD10, CD19, CD20, CD34, CD38, and CD45 expression in regenerative-BCP (early, BCP1 and late, BCP2) from 200 BALL-MRD samples, and compared them with BCP from 15 regenerating control (RC) TALL-MRD samples and 20 treatment-naïve bone-marrow control (TNSC) samples. Regenerative-BCP1 showed downregulation in CD10 and CD34 expression with increased CVIF and reduced nMFI (p < 0.001), upregulation of CD20 with increased nMFI (p = 0.014) and heterogeneous CD45 expression with increased CVIF (p < 0.001). Immunophenotypic shift was less pronounced in the BCP2 compared to BCP1 compartment with increased CVIF in all but CD45 (p < 0.05) and reduced nMFI only in CD45 expression (p = 0.005). Downregulation of CD10/CD34 and upregulation of CD20 was higher at EOI than EOC and SFU time-points (p < 0.001). Regenerative-BCPs are characterized by the significant immunophenotypic shift in commonly used B-ALL-MRD markers, especially CD10 and CD34 expression, as compared to treatment-naïve BCPs. Therefore, the templates/database for BMRD analysis must be developed using regenerative-BCP.

Microfluidic Chip based direct triple antibody immunoassay for monitoring patient comparative response to leukemia treatment

We report a time and cost-efficient microfluidic chip for screening the leukemia cells having three specific antigens. In this method, the target blast cells are double sorted with immunomagnetic beads and captured by the 3rd antibody immobilized on the gold surface in a microfluidic chip. The captured blast cells in the chip were imaged using a bright-field optical microscope and images were analyzed to quantify the cells. First sorting was performed with nano size immunomagnetic beads and followed by 2nd sorting where micron size immunomagnetic beads were used. The low-cost microfluidic platform is made of PMMA and glass including micro size gold pads. The developed microfluidic platform was optimized with cultured B type lymphoblast cells and tested with the samples of leukemia patients. The 8 bone marrow samples of 4 leukemia patients on the initial diagnosis and on the 15th day after the start of the chemotherapy treatment were tested both with the developed microfluidic platform and the flow cytometry. A 99% statistical agreement between the two methods shows that the microfluidic chip is able to monitor the decrease in the number of blast cells due to the chemotherapy. The experiments with the patient samples demonstrate that the developed system can perform relative measurements and have a potential to monitor the patient response to the applied therapy and to enable personalized dose adjustment.

Immunophenotypic modulation in pediatric B lymphoblastic leukemia and its implications in MRD detection

Minimal/Measurable residual disease (MRD) is the most reliable and powerful indicator of prognosis in B cell precursor acute lymphoblastic leukemia (BCP-ALL). Modulation of antigenic expression in leukemic cells is known to occur postchemotherapy and thus carries a potential risk of false MRD quantification by flowcytometry. We studied the immunophenotypic modulation of nine antigens in residual leukemic cells at postinduction MRD assessment in 31 BCP - ALL children. We found significant downmodulation of CD10, CD38, CD58, CD81 and upmodulation of CD19, CD45 in leukemic cells. Downmodulation of CD34 was observed but was not statistically significant. Expression of CD20 and CD22 remained stable in most of the cases. MRD-positive cases showed loss of diagnostic LAIP and some showed gain of new LAIP compared to baseline. Various combination of antibodies including the novel markers should be incorporated into the panel to increase the sensitivity of MRD detection.

Proteomic tools and new insights for the study of B-cell precursor acute lymphoblastic leukemia

B-cell precursor acute lymphoblastic leukemia (BCP-ALL) is a hematological malignancy of immature B-cell precursors, affecting children more often than adults. The etiology of BCP-ALL is still unknown, but environmental factors, sex, race or ethnicity, and genomic alterations influence the development of the disease. Tools based on protein detection, such as flow cytometry, mass spectrometry, mass cytometry and reverse phase protein array, represent an opportunity to investigate BCP-ALL pathogenesis and to identify new biomarkers of disease. This review aims to document the recent advancements with respect to applications of proteomic technologies to study mechanisms of leukemogenesis, how this information could be used in the discovery of biological targets, and finally we describe the challenges of application of proteomic tools for the approach of BCP-ALL.

Reassessment of the Risk-stratified GD-2008 ALL Protocol

OBJECTIVE

To explore the clinical features and outcomes of relapsed childhood acute lymphoblastic leukemia (ALL) at our center, achieve the early detection of risk factors for recurrence and assess the risk-stratified Guangdong (GD)-2008 ALL protocol.

MATERIALS AND METHODS

In total, 59 Chinese childhood ALL patients treated with the GD-2008 ALL protocol who relapsed between July 2008 and March 2015 were enrolled in this study. Their clinical features and outcomes were retrospectively analyzed and compared with those of 218 patients who achieved continuous complete remission.

RESULTS

Of the 285 study participants, 8 died of treatment-related infections or other complications before remission, 218 achieved continuous complete remission, and 59 patients relapsed, yielding a relapse rate of 20.7%. The number of relapsed patients in the standard-risk, intermediate-risk, and high-risk groups were 15 (17.0%), 27 (19.7%), and 17 (32.7%), respectively. Risk factors included age 10 years and above at first diagnosis, white blood cell (WBC) count ≥50×10/L, poor prednisone response, failure to achieve bone marrow complete remission at day 15 of induction chemotherapy. High-risk stratification and a high level (≥0.1%) of minimal residual disease at day 33 were the risk factors for relapse. Multivariate analysis showed that a high WBC at first diagnosis was an independent risk factor for relapse (P=0.000).

CONCLUSION

For the GD-2008 ALL risk stratification based on age and initial WBC, 10 years of age and WBC 50×10/L can be used as cut-offs. Patients at high risk benefited from the GD-2008 ALL protocol. In addition, the impact of minimal residual disease on prognosis should be considered.

No prognostic significance of immunophenotypic changes at the end of remission induction therapy in children with B-lineage acute lymphoblastic leukemia

Detection of aberrant antigen expression in acute lymphoblastic leukemia (ALL) by flow cytometric is proposed for the quantification of minimal residual disease (MRD). There are few studies that investigate the stability of the antigen expression in children with B lineage ALL at the end of remission induction therapy and determine its prognostic impact. Between 2010 and 2015, 691 bone marrow specimens of childhood ALL were sent at diagnosis for immunophenotypic characterization, and follow-up samples for MRD were analyzed on day 33. Of these, 155 patients with MRD more than or equal to 0.01% were eligible for the study. Immunophenotypic studies were performed by multiparametric flow cytometry using four-colour monoclonal antibody combinations. Overall, 86 of 155 (55.5%) cases showed phenotype shifts at least one marker. CD19 was the most stable markers. By contrast, CD20 was significantly different between diagnosis and day 33 in nearly one third of the cases. Shifts of antigen expression was not significantly associated with EFS, RFS or OS (P > 0.05). Multivariate analysis showed that WBC and BCR-ABL have independent prognostic value in childhood ALL. Changes in antigen expressions were commonly occurred at the end of induction and not associated with prognostic value in patients whose MRD were positive on day 33.

Prognostic Effect of CD20 Expression in Adult B-cell Acute Lymphoblastic Leukemia

INTRODUCTION

The expression of the CD20 on adult B-cell acute lymphoblastic leukemia (ALL-B) has generally been associated with a poor prognosis, and several studies have explored the incorporation of rituximab into the therapeutic regimen for adult ALL-B patients, with a positive effect on event-free survival (EFS).

PATIENTS AND METHODS

We analyzed the prognostic value of CD20 expression and the effect of rituximab for the treatment of Hispanic adult ALL-B patients. We performed a retrospective study of 152 ALL-B patients treated from 2009 to 2016. The patient characteristics and treatment outcomes were analyzed according to CD20 expression (CD20⁺ vs. CD20^-), age group, and treatment with rituximab.

RESULTS

CD20 expression was positive for 47.7% of patients (n = 72). Excluding the patients who had received rituximab, the overall survival (OS) was greater for the CD20^- patient subgroup than for the CD20⁺ subgroup (11.2 vs. 6.9 months; 95% confidence interval [CI], 7.43-14.9; P = .008). In the CD20⁺ subgroup, 10 patients (7.2%) received treatment with rituximab, with 100% reaching complete remission (CR) 4 weeks after treatment. In the 18- to 39-year age group, CD20⁺ patients treated with rituximab had EFS and OS that was not reached. In addition, for CD20⁺ patients who received with chemotherapy, EFS was 3.9 months (95% CI, 0.6-7.2 months; P = .025) and OS was 7.2 months (95% CI, 3.37-11.0; P = .013). Multivariate analysis showed that the use of rituximab was independently associated with OS and CR at 4 weeks after induction.

CONCLUSION

CD20 expression in adult ALL-B is associated with decreased OS. Treatment with rituximab can increase OS, EFS, and CR in the 18- to 39-year age group.

Endoglin: a novel target for therapeutic intervention in acute leukemias revealed in xenograft mouse models

Endoglin (CD105), a receptor of the transforming growth factor-β superfamily, has been reported to identify functional long-term repopulating hematopoietic stem cells, and has been detected in certain subtypes of acute leukemias. Whether this receptor plays a functional role in leukemogenesis remains unknown. We identified endoglin expression on the majority of blasts from patients with acute myeloid leukemia (AML) and acute B-lymphoblastic leukemia (B-ALL). Using a xenograft model, we find that CD105⁺ blasts are endowed with superior leukemogenic activity compared with the CD105^- population. We test the effect of targeting this receptor using the monoclonal antibody TRC105, and find that in AML, TRC105 prevented the engraftment of primary AML blasts and inhibited leukemia progression following disease establishment, but in B-ALL, TRC105 alone was ineffective due to the shedding of soluble CD105. However, in both B-ALL and AML, TRC105 synergized with reduced intensity myeloablation to inhibit leukemogenesis, indicating that TRC105 may represent a novel therapeutic option for B-ALL and AML.