Minimal residual disease quantification by flow cytometry provides reliable risk stratification in T-cell acute lymphoblastic leukemia

Minimal residual disease (MRD) measured by PCR of clonal IgH/TCR rearrangements predicts relapse in T-cell acute lymphoblastic leukemia (T-ALL) and serves as risk stratification tool. Since 10% of patients have no suitable PCR-marker, we evaluated flowcytometry (FCM)-based MRD for risk stratification. We included 274 T-ALL patients treated in the NOPHO-ALL2008 protocol. MRD was measured by six-color FCM and real-time quantitative PCR. Day 29 PCR-MRD (cut-off 10-3) was used for risk stratification. At diagnosis, 93% had an FCM-marker for MRD monitoring, 84% a PCR-marker, and 99.3% (272/274) had a marker when combining the two. Adjusted for age and WBC, the hazard ratio for relapse was 3.55 (95% CI 1.4-9.0, p = 0.008) for day 29 FCM-MRD ≥ 10-3 and 5.6 (95% CI 2.0-16, p = 0.001) for PCR-MRD ≥ 10-3 compared with MRD < 10-3. Patients stratified to intermediate-risk therapy on day 29 with MRD 10-4-<10-3 had a 5-year event-free survival similar to intermediate-risk patients with MRD < 10-4 or undetectable, regardless of method for monitoring. Patients with day 15 FCM-MRD < 10-4 had a cumulative incidence of relapse of 2.3% (95% CI 0-6.8, n = 59). Thus, FCM-MRD allows early identification of patients eligible for reduced intensity therapy, but this needs further studies. In conclusion, FCM-MRD provides reliable risk prediction for T-ALL and can be used for stratification when no PCR-marker is available.

Altered profile of immune regulatory cells in the peripheral blood of lymphoma patients

BACKGROUND

Regulatory immune cells may modulate the lymphoma microenvironment and are of great interest due to the increasing prevalence of treatment with immunotherapies in lymphoma patients. The aim was to explore the composition of different immune regulatory cell subsets in the peripheral blood of newly diagnosed lymphoma patients in relation to treatment outcome.

METHODS

Forty-three newly diagnosed patients with lymphoma were included in the study; 24 with high-grade B-cell lymphoma (HGBCL) and 19 with classical Hodgkin lymphoma (cHL). Peripheral blood was prospectively collected and immune regulatory cells were identified by multi-color flow cytometry and analyzed in relation to healthy blood donors and clinical characteristics and outcome.

RESULTS

The percentage of CD3-positive T-cells was lower (p = 0.03) in the peripheral blood of lymphoma patients at diagnosis compared to healthy blood donors regardless of lymphoma subtype, although statistically, neither the percentage of monocytes (p = 0.2) nor the T-cell/monocyte ratio (p = 0.055) differed significantly. A significant decrease in the percentage of a subset of regulatory NK cells (CD7⁺/CD3^-/CD56^bright/CD16^dim/-) was identified in the peripheral blood of lymphoma patients compared to healthy blood donors (p = 0.003). Lymphoma patients also had more granulocytic myeloid-derived suppressor cells (MDSCs) (p = 0.003) compared to healthy blood donors, whereas monocytic MDSCs did not differ significantly (p = 0.07). A superior disease-free survival was observed for cHL patients who had an increase in the percentage of granulocytic MDSCs (p = 0.04).

CONCLUSIONS

An altered profile of immune cells in the peripheral blood with a decrease in T-cells and regulatory NK-cells was observed in newly diagnosed lymphoma patients. CHL patients with higher percentages of regulatory NK cells and higher percentages of granulocytic MDSCs might have a better outcome, although the number of patients was low.

Both CD4+ FoxP3+ and CD4+ FoxP3- T cells from patients with B-cell malignancy express cytolytic markers and kill autologous leukaemic B cells in vitro

Cytotoxic CD4(+) T cells have been found in patients with chronic lymphocytic leukaemia (CLL) and seem to be involved in the regulation of malignant B cells. The CD4(+) T regulatory cells (Tregs) can regulate various immune cells, including B cells, by inducing their apoptosis. Hence, different subgroups of CD4(+) T cells may be involved in the regulation of malignant B cells. In this study, the cytotoxic phenotype and function of various CD4(+) T-cell subgroups were investigated in patients with B-cell malignancies. Peripheral blood was collected from patients with CLL, various B-cell lymphomas, healthy adult donors, children with precursor B-cell acute lymphoblastic leukaemia (pre-B ALL) and from healthy children. CD4(+) T cells (CD3(+) CD4(+)  FoxP3(-)), Tregs (CD3(+) CD4(+) CD127(low) FoxP3(+)) and CD127(high) FoxP3(+) T cells (CD3(+) CD4(+) CD127(high) FoxP3(+)) were analysed for their expression of the cytolytic markers CD107a and Fas ligand. Patients with CLL had increased CD107a expression on all tested T-cell subgroups compared with healthy donors. Similar results were found in patients with B-cell lymphomas whereas the CD107a expression in children with pre-B ALL was no different from that in healthy controls. Fas ligand expression was similar between patient cells and cells of healthy donors. CD4(+) T cells and Tregs from patients with CLL and healthy donors were subsequently purified and cultured in vitro with autologous B cells. Both subgroups lysed B cells and killing was confirmed by granzyme ELISAs. In conclusion, cytotoxic populations of CD4(+) T cells, including Tregs, are present in patients with B-cell malignancy and may be an important factor in immune-related disease control.

Minimal residual disease assessment in childhood acute lymphoblastic leukaemia: a Swedish multi-centre study comparing real-time polymerase chain reaction and multicolour flow cytometry

Minimal residual disease (MRD) assessment is a powerful prognostic factor for determining the risk of relapse in childhood acute lymphoblastic leukaemia (ALL). In this Swedish multi-centre study of childhood ALL diagnosed between 2002 and 2006, the MRD levels were analysed in 726 follow-up samples in 228 children using real-time quantitative polymerase chain reaction (RQ-PCR) of rearranged immunoglobulin/T-cell receptor genes and multicolour flow cytometry (FCM). Using an MRD threshold of 0·1%, which was the sensitivity level reached in all analyses, the concordance between RQ-PCR and FCM MRD values at day 29 was 84%. In B-cell precursor ALL, an MRD level of ≥0·1% at day 29 predicted a higher risk of bone marrow relapse (BMR) with both methods, although FCM was a better discriminator. However, considering the higher median MRD values achieved with RQ-PCR, a higher MRD cut-off (≥0·2%) improved the predictive capacity of RQ-PCR. In T-ALL, RQ-PCR was notably superior to FCM in predicting risk of BMR. That notwithstanding, MRD levels of ≥0·1%, detected by either method at day 29, could not predict isolated extramedullary relapse. In conclusion, the concordance between RQ-PCR and FCM was high and hence both methods are valuable clinical tools for identifying childhood ALL cases with increased risk of BMR.

Applicability of IG/TCR gene rearrangements as targets for minimal residual disease assessment in a population-based cohort of Swedish childhood acute lymphoblastic leukaemia diagnosed 2002-2006

Minimal residual disease (MRD) detection during the early treatment phase has become an important stratification parameter in many childhood acute lymphoblastic leukaemia (ALL) treatment protocols. Here, we aimed to address the applicability of rearranged antigen-receptor genes as potential MRD markers using real-time quantitative polymerase chain reaction (RQ-PCR) in a Swedish population-based cohort. From 334 childhood ALL cases diagnosed during 2002-2006, we analysed 279 diagnostic samples (84%) by screening for rearranged immunoglobulin (IG) and T-cell receptor (TCR) genes. Allele-specific oligonucleotides were designed, and the sensitivity and quantitative level was determined for each target. Overall, clonal IG/TCR rearrangements were detected in 97% (236/244) of B-cell precursor ALL (BCP ALL) and 94% (33/35) of T-ALL. A sensitive RQ-PCR analysis (< or = 10(-4)) was obtained in 89% (216/244) of BCP ALL and in 74% (26/35) of T-ALL, whereas two sensitive targets were only available in 47% (115/244) of BCP ALL and 29% (10/35) of T-ALL cases. With the stratification threshold of > or = 10(-3), which is applied in the current Nordic treatment protocol (NOPHO-ALL 2008) for the identification of high-risk patients, 93% of BCP ALL and 86% of T-ALL reached this quantitative range by at least one target gene. Taken together, this national retrospective study demonstrates that an IG/TCR target for MRD monitoring can be identified in the majority of childhood ALL cases, whereas identification of a second sensitive target gene needs to be improved.

The impact of RNA stabilization on minimal residual disease assessment in chronic myeloid leukemia

BACKGROUND AND OBJECTIVES

Accurate quantification of BCR-ABL mRNA is of critical importance for managing patients with chronic myeloid leukemia (CML) who are receiving imatinib therapy. RNA degradation thus constitutes a potential problem for laboratories quantifying minimal residual disease (MRD). Patients' samples that take a long time to be transported from the hospital to the analyzing laboratory may be subject to RNA degradation with a corresponding loss in sensitivity and possible generation of false negative results. Recently, RNA preservation systems have been developed in order to improve RNA stability. The aim of the present study was to investigate such a system.

DESIGN AND METHODS

We evaluated the performance of the PAXgene Blood RNA Kit in follow-up CML peripheral blood samples and compared the results to those from unstabilized parallel Trizol extracted samples. The different sample processing methods were evaluated by real-time polymerase chain reaction (PCR) analysis.

RESULTS

RNA isolated with the PAXgene system gave a superior yield per milliliter of blood than did the routine Trizol extraction method. However, although of comparable quality, the RNA did not PCR-amplify as efficiently as equal amounts of RNA from routinely processed samples. Therefore, RNA processed with the PAXgene system showed decreased sensitivity for MRD detection, resulting in false negative results. The sensitivity was comparable to that of samples processed routinely 20-30 hours after phlebotomy.

INTERPRETATION AND CONCLUSIONS

We conclude that routinely processed, i.e. unstabilized, peripheral blood that reaches the laboratory and is processed within 30 hours is preferable for MRD detection. Optimal results were achieved with fresh samples processed within 5 hours with the Trizol method. However, RNA stabilization may be useful if sample transit is expected to exceed 30 hours.

Somatically mutated Ig V(H)3-21 genes characterize a new subset of chronic lymphocytic leukemia

Recent studies on the immunoglobulin variable heavy chain (IgV(H)) genes have revealed that B-cell chronic lymphocytic leukemia (B-CLL) consists of at least 2 clinical entities with either somatically mutated or unmutated V(H) genes. We have analyzed the V(H) gene mutation status and V(H) gene usage in 119 B-CLL cases and correlated them to overall survival. A novel finding was the preferential use of the V(H)3-21 gene in mutated cases, whereas biased V(H)1-69 gene usage was found in unmutated cases as previously reported. Interestingly, the subset of mutated cases using the V(H)3-21 gene displayed distinctive genotypic/phenotypic characteristics with shorter average length of the complementarity determining region 3 and clonal expression of lambda light chains. In addition, this mutated subset showed significantly shorter survival than other mutated cases and a similar clinical course to unmutated cases. We therefore suggest that B-CLL cases with mutated V(H)3-21 genes may constitute an additional entity of B-CLL.