Combination of CD160 and CD200 as a useful tool for differential diagnosis between chronic lymphocytic leukemia and other mature B-cell neoplasms

The kappa/lambda ratio of surface immunoglobulin light chain as a valuable parameter for MRD assessment in CLL with atypical immunophenotype

In recent years, the significance of detecting minimal/measurable residual disease (MRD) in chronic lymphocytic leukemia (CLL) has increased due to the availability of highly effective therapeutic agents. Flow cytometry provides notable cost-effectiveness and immediacy, with an expected sensitivity level of approximately 10-4. The critical aspect of MRD detection via flow cytometry lies in accurately defining the region containing tumor cells. However, a subset of CLL, known as CLL with atypical immunophenotype, exhibits a distinct cell surface marker expression pattern that can make MRD detection challenging, because these markers often resemble those of normal B cells. To enhance the sensitivity of MRD detection in such atypical cases of CLL, we have capitalized on the observation that cell surface immunoglobulin (sIg) light chains tend to be expressed at a higher level in this subtype. For every four two-dimensional plots of cell surface markers, we used a plot to evaluate the expression of sIg kappa/lambda light chains and identified regions where the kappa/lambda ratio of sIg light chains deviated from a designated threshold within the putative CLL cell region. Using this method, we could detect atypical CLL cells at a level of 10-4. We propose this method as an effective MRD assay.

What Does Atypical Chronic Lymphocytic Leukemia Really Mean? A Retrospective Morphological and Immunophenotypic Study

Atypical chronic lymphocytic leukemia (CLL) is still defined according to morphological criteria. However, deviance from the typical surface immunological profile suggests an atypical immunological-based CLL. A large cohort of patients with CLL was retrospectively evaluated aiming at assessing morphological (FAB criteria), immunophenotypical (two or more discordances from the typical profile), and clinical-biological features of atypical CLL. Compared to typical cases, morphologically atypical CLL showed a greater percentage of unmutated IgVH and CD38 positivity, and a higher expression of CD20. Immunophenotypically atypical CLL was characterized by more advanced clinical stages, higher expression of CD20, higher rate of FMC7, CD79b and CD49d positivity, and by an intermediate-high expression of membrane surface immunoglobulin, compared to typical cases. When patients were categorized based on immunophenotypic and morphologic concordance or discordance, no difference emerged. Finally, morphological features better discriminated patients' prognosis in terms of time-to-first treatment, while concordant atypical cases showed overall a worse prognosis. Discordant cases by immunophenotype and/or morphology did not identify specific prognostic groups. Whether-in the era of molecular markers used as prognostic indicators-it does make sense to focus on morphology and immunophenotype features in CLL is still matter of debate needing further research.

Current Approaches of Immune Checkpoint Therapy in Chronic Lymphocytic Leukemia

OPINION STATEMENT

Increasing understanding of the complex interaction between leukemic and immune cells, which is responsible for tumor progression and immune evasion, has paved the way for the development of novel immunotherapy approaches in chronic lymphocytic leukemia (CLL). One of the well-known immune escape mechanisms of tumor cells is the up-regulation of immune checkpoint molecules. In recent years, targeting immune checkpoint receptors is the most clinically effective immunotherapeutic strategy for cancer treatment. In this regard, various immune checkpoint blockade (ICB) drugs are currently been investigating for their potential effects on improving anti-tumor immune response and clinical efficacy in the hematological malignancies; however, their effectiveness in patients with CLL has shown less remarkable success, and ongoing research is focused on identifying strategies to enhance the efficacy of ICB in CLL.

Methodological and conceptual challenges to the flow cytometric classification of leukemic lymphoproliferative disorders

The diagnosis of leukemic B-cell lymphoproliferative disorders (B-LPDs) is made by integrating clinical, cytological, cytometric, cytogenetic, and molecular data. This leaves room for differences and inconsistencies between experts. In this study, we examine methodological and conceptual aspects of the flow cytometric classification of leukemic B-LPDs that could explain them. Among methodological aspects, we discuss (1) the different statistical tests used to select and evaluate markers, (2) how these markers are analyzed, (3) how scores are interpreted, (4) different degrees to which diagnostic information is used, and (5) and the impact of differences in study populations. Among conceptual aspects, we discuss (1) challenges to integrating different biological data points, (2) the under examination of the costs of misclassification (false positives and false negatives), and finally, (3) we delve into the impact of the lack of a true diagnostic gold standard and the indirect evidence suggesting poor reproducibility in the diagnosis of leukemic B-LPDs. We then outline current harmonization efforts and our personal approach. We conclude that numerous flow cytometry scores and diagnostic systems are now available; however, as long as the considerations discussed remain unaddressed, external reproducibility and interobserver agreement will not be achieved, and the field will not be able to move forward if a true gold standard is not found.

BTLA/HVEM Axis Induces NK Cell Immunosuppression and Poor Outcome in Chronic Lymphocytic Leukemia

Simple Summary

Chronic lymphocytic leukemia (CLL) represents the most frequent B cell malignancy in Western countries and still remains as an incurable disease. Despite recent advances in targeted therapies including ibrutinib, idelalisib or venetoclax, resistance mechanisms have been described and patients develop a progressive immunosuppression. Since immune checkpoint blockade has demonstrated to reinvigorate T and NK cell-mediated anti-tumor responses, the aim of this work was to elucidate whether this immunosuppression relies, at least in part, in BTLA/HVEM axis in patients with CLL. Our results demonstrate that BTLA and HVEM expression is deeply dysregulated on leukemic and NK cells and correlates with poor outcome. Moreover, soluble BTLA levels correlated with adverse cytogenetics and shorter time to treatment. BTLA blockade restored, at least in part, NK cell-mediated responses in patients with CLL. Altogether, our results provide the rationale to further investigate the role of BTLA/HVEM axis in the pathogenesis of CLL.

Abstract

Chronic lymphocytic leukemia (CLL) is characterized by progressive immunosuppression and diminished cancer immunosurveillance. Immune checkpoint blockade (ICB)-based therapies, a major breakthrough against cancer, have emerged as a powerful tool to reinvigorate antitumor responses. Herein, we analyzed the role of the novel inhibitory checkpoint BTLA and its ligand, HVEM, in the regulation of leukemic and natural killer (NK) cells in CLL. Flow cytometry analyses showed that BTLA expression is upregulated on leukemic cells and NK cells from patients with CLL, whereas HVEM is downregulated only in leukemic cells, especially in patients with advanced Rai-Binet stage. In silico analysis revealed that increased HVEM, but not BTLA, mRNA expression in leukemic cells correlated with diminished overall survival. Further, soluble BTLA (sBTLA) was found to be increased in the sera of patients with CLL and highly correlated with poor prognostic markers and shorter time to treatment. BTLA blockade with an anti-BTLA monoclonal antibody depleted leukemic cells and boosted NK cell-mediated responses ex vivo by increasing their IFN-γ production, cytotoxic capability, and antibody-dependent cytotoxicity (ADCC). In agreement with an inhibitory role of BTLA in NK cells, surface BTLA expression on NK cells was associated with poor outcome in patients with CLL. Overall, this study is the first to bring to light a role of BTLA/HVEM in the suppression of NK cell-mediated immune responses in CLL and its impact on patient’s prognosis, suggesting that BTLA/HVEM axis may be a potential therapeutic target in this disease.

The contribution of CD200 to the diagnostic accuracy of Matutes score in the diagnosis of chronic lymphocytic leukemia in limited resources laboratories

Flow cytometry immunophenotyping has an essential role in distinguishing chronic lymphocytic leukemia from other B-chronic lymphoproliferative disorders. Recently, CD200 is considered as a relatively consistent marker in chronic lymphocytic leukemia. We retrospectively assessed CD200 expression in 252 patients with B chronic lymphoproliferative disorders with four-color flow cytometry. CD200 expression estimation included the proportion of positive cells (≥30%) and the mean fluorescence intensity ratio. Additionally, we have incorporated CD200 into Matutes score, also replaced FMC7 and CD79b in an attempt to improve the score discriminative power. Of 252 patients enrolled, 199(79%) patients were classified as chronic lymphocytic leukemia and 53 (21%) as other B-chronic lymphoproliferative disorders. All chronic lymphocytic leukemia cases and 20 of 53 (37.7%) of other B-chronic lymphoproliferative disorders demonstrated high CD200 expression (≥30%). Further, CD200 (≥30%) revealed a higher accuracy in comparison to other markers in Matutes score (range: 51%–92.5%). Also, CD200 addition to the Matutes score has correctly recognized all 199 chronic lymphocytic leukemia cases including 10 atypical chronic lymphocytic leukemia cases. As for non-CLL cases, 20 of 53 attained a higher score, yet keeping the original diagnosis. Moreover, CD200 enhanced the diagnostic accuracy of Matutes score to 100%, and when included in a simplified 4-markers score, showed an accuracy of 99.8% compared to 99.4% of Matutes score. In conclusion, CD200 is an accurate diagnostic marker for chronic lymphocytic leukemia, and can refine the modified Matutes score accuracy when added with other markers.

CD200 and Chronic Lymphocytic Leukemia: Biological and Clinical Relevance

CD200, a transmembrane type Ia glycoprotein belonging to the immunoglobulin protein superfamily, is broadly expressed on a wide variety of cell types, such as B lymphocytes, a subset of T lymphocytes, dendritic cells, endothelial and neuronal cells. It delivers immunosuppressive signals through its receptor CD200R, which is expressed on monocytes/myeloid cells and T lymphocytes. Moreover, interaction of CD200 with CD200R has also been reported to play a role in the regulation of tumor immunity. Overexpression of CD200 has been reported in chronic lymphocytic leukemia (CLL) and hairy cell leukemia but not in mantle cell lymphoma, thus helping to better discriminate between these different B cell malignancies with different prognosis. In this review, we focus on the role of CD200 expression in the differential diagnosis of mature B-cell neoplasms and on the prognostic significance of CD200 expression in CLL, where conflicting results have been published so far. Of interest, increasing evidences indicate that anti-CD200 treatment might be therapeutically beneficial for treating CD200-expressing malignancies, such as CLL.

Measurable residual disease in the treatment of chronic lymphocytic leukemia

Treatment outcomes of chronic lymphocytic leukemia (CLL) have improved since chemoimmunotherapy and novel drugs became available for CLL treatment; therefore, more sensitive methods to evaluate residual CLL cells in patients are required. Measurable residual disease (MRD) has been assessed in several clinical trials on CLL using flow cytometry, real-time quantitative PCR (RQ-PCR) with allele-specific oligonucleotide (ASO) primers, and high-throughput sequencing. MRD assessment is useful to predict the treatment outcomes in the context of chemotherapy and treatment with novel drugs such as venetoclax. In this review, we discuss major techniques for MRD assessment, data from relevant clinical trials, and the future of MRD assessment in CLL treatment.

Determination of CD43 and CD200 surface expression improves accuracy of B-cell lymphoma immunophenotyping

BACKGROUND

The Matutes score (MS) was proposed to differentiate chronic lymphocytic leukemia (CLL) from other B-cell non-Hodgkin lymphomas (B-NHLs). However, ambiguous immunophenotypes are common and remain a diagnostic challenge. Therefore, we evaluated the diagnostic benefit of measuring CD200 and CD43 expression together with the standard MS antigens.

METHODS

138 lymphoma patient samples and a validation cohort of 138 additive samples were classified according to the standard MS and further assigned with one or two additional points, for high CD200 and/or CD43 expression levels. The "classical" MS and the "Matutes score-extended" (MS-e) were categorized as high (4-5/6-7), intermediate (2-3/4-5), and low (0-1/0-3). Samples were reclassified into the MS-e with focus on ambiguous cases with an intermediate "classical" MS.

RESULTS

A total of 35 of 138 (25.4%) patient samples were assigned to the intermediate MS group and confirmed by histopathological reports as CLL (14/40.0%) and B-NHLs other than CLL (21/60%). MS-e analysis identified 13 of 14 (92.9%) of CLL cases (MS-e 4-5) and 18/21 (85.7%) non-CLL cases (MS-e ≤ 3) correctly. Overall, the sensitivity of the CLL diagnosis was significantly increased by application of MS-e compared to the "classical" MS (98.8% vs. 82.7%; p = 0.0009), while specificity of both methods was almost equal (94.7% vs. 98.3%; p = 0.4795). Of note, sole measurement of CD43 and CD200 on B-cells sufficiently differentiated CLL from non-CLL with a test accuracy superior to the "classical" MS (F1 score 96.2 vs. 93.6).

CONCLUSION

CD200 and CD43 have a high informative value in diagnostic immunophenotyping and facilitate the separation of CLL from other B-NHLs particularly in ambiguous cases.

HVEM network signaling in cancer

Somatic mutations in cancer cells may influence tumor growth, survival, or immune interactions in their microenvironment. The tumor necrosis factor receptor family member HVEM (TNFRSF14) is frequently mutated in cancers and has been attributed a tumor suppressive role in some cancer contexts. HVEM functions both as a ligand for the lymphocyte checkpoint proteins BTLA and CD160, and as a receptor that activates NF-κB signaling pathways in response to BTLA and CD160 and the TNF ligands LIGHT and LTα. BTLA functions to inhibit lymphocyte activation, but has also been ascribed a role in stimulating cell survival. CD160 functions to co-stimulate lymphocyte function, but has also been shown to activate inhibitory signaling in CD4⁺ T cells. Thus, the role of HVEM within diverse cancers and in regulating the immune responses to these tumors is likely context specific. Additionally, development of therapeutics that target proteins within this network of interacting proteins will require a deeper understanding of how these proteins function in a cancer-specific manner. However, the prominent role of the HVEM network in anti-cancer immune responses indicates a promising area for drug development.

Reduced CD160 Expression Contributes to Impaired NK-cell Function and Poor Clinical Outcomes in Patients with HCC

: We previously reported that deficiencies in natural killer (NK)-cell number and function play an important role in the progression of hepatocellular carcinoma (HCC). However, the mechanisms underlying this phenomenon remain obscure. In this study, we analyzed the expression of CD160 on intrahepatic NK cells by evaluating peritumoral and intratumoral tissues of 279 patients with HCC and 20 healthy livers. We observed reduced expression of CD160 on intratumoral NK cells, and patients with lower CD160 cell densities within tumors exhibited worse disease and a higher recurrence rate. High-resolution microarray and gene set enrichment analysis of flow cytometry-sorted primary intrahepatic CD160⁺ and CD160^- NK cells of healthy livers indicated that human CD160⁺ NK cells exhibited functional activation, high IFNγ production, and NK-mediated immunity. In addition, global transcriptomic analysis of sorted peritumoral and intratumoral CD160⁺ NK cells revealed that intratumoral CD160⁺ NK cells are more exhausted than peritumoral CD160⁺ NK cells and produce less IFNγ. High levels of TGFβ1 interfered with production of IFNγ by CD160⁺ NK cells, blocking of which specifically restored IFNγ production in CD160⁺ NK cells to normal levels. These findings indicate that reduced numbers of CD160⁺ NK cells, together with the functional impairment of CD160⁺ NK cells by TGFβ1, contribute to tumor immune escape. In addition, restoring the expression of CD160 and blocking TGFβ1 appear a promising therapeutic strategy against liver cancer. SIGNIFICANCE: These findings show that reduced number and function of CD160⁺ NK cells in the tumor microenvironment contributes to immune escape of HCC; blocking TGFβ1 restores IFNγ production of CD160⁺ NK cells.Graphical Abstract: http://cancerres.aacrjournals.org/content/canres/78/23/6581/F1.large.jpg.

CD200 is a useful diagnostic marker for identifying atypical chronic lymphocytic leukemia by flow cytometry

INTRODUCTION

Immunophenotyping by flow cytometry is routinely employed in distinguishing between chronic lymphocytic leukemia (CLL) and mantle cell lymphoma (MCL). Inclusion of CD200 has been reported to contribute to more reliable differentiation between CLL and MCL. We investigated the value of CD200 in assessment of atypical CLL cases.

METHODS

CD200 expression on mature B cell neoplasms was studied by eight-color flow cytometry in combination with a conventional panel of flow cytometry markers. The study included 70 control samples, 63 samples with CLL or atypical CLL phenotype, 6 MCL samples, and 40 samples of other mature B cell neoplasms.

RESULTS

All CLL samples were positive for CD200, whereas MCL samples were dim or negative for CD200. Of the CLL samples, 7 were atypical by conventional flow cytometry, with Matutes scores ≤3. These cases were tested for evidence of a t(11;14) translocation, characteristic of MCL, and all were negative, consistent with their classification as atypical CLL. All these atypical CLL samples were strongly positive for CD200.

CONCLUSION

CD200 proved to be a useful marker for differentiation between CLL and MCL by flow cytometry. In particular, CD200 was useful in distinguishing CLL samples with atypical immunophenotypes from MCL.

Flow Cytometric Patterns of CD200 and CD1d Expression Distinguish CD10-Negative, CD5-Negative Mature B-Cell Lymphoproliferative Disorders

OBJECTIVES

The importance of distinguishing mature B-cell lymphoproliferative disorders (B-LPDs) is highlighted by the distinct treatments used for and varying prognoses seen in association with these different diseases. Immunophenotyping allows for accurate and efficient differentiation of many B-LPDs. Recently, we showed that CD200 is highly expressed in hairy cell leukemia (HCL) but not in marginal zone lymphoma (MZL), lymphoplasmacytic lymphoma (LPL), or hairy cell leukemia-variant (HCL-v). Here, we assessed the usefulness of a flow cytometric panel combining CD200 and CD1d with CD25, CD103, and CD11c to distinguish CD10-, CD5- B-LPDs.

METHODS

We analyzed the expression of CD200 and CD1d by flow cytometric analysis in 79 cases of CD10-, CD5- mature B-LPDs.

RESULTS

Distinct patterns of CD200 and CD1d expression were seen in the examined B-LPDs. HCL showed bright positivity for CD200 along with positive staining for CD1d, whereas HCL-v showed low levels of expression for both markers. LPL demonstrated positive staining for CD200 in combination with dim to negative staining for CD1d. In contrast, MZL was commonly positive for CD1d and negative for CD200.

CONCLUSIONS

Flow cytometric analysis of CD200 and CD1d, along with CD25, CD103, and CD11c, can aid in the diagnosis of CD10-, CD5- mature B-LPDs.