Immunophenotypes in "classical" B-cell chronic lymphocytic leukemia. Correlation with normal cellular counterpart and clinical findings

CD38/NAD+ glycohydrolase and associated antigens in chronic lymphocytic leukaemia: From interconnected signalling pathways to therapeutic strategies

Chronic lymphocytic leukaemia (CLL) is a heterogenous disease characterized by the accumulation of neoplastic CD5+/CD19+ B lymphocytes. The spreading of the leukaemia relies on the CLL cell's ability to survive in the blood and migrate to and proliferate within the bone marrow and lymphoid tissues. Some patients with CLL are either refractory to the currently available therapies or relapse after treatment; this emphasizes the need for novel therapeutic strategies that improving clinical responses and overcome drug resistance. CD38 is a marker of a poor prognosis and governs a set of survival, proliferation and migration signals that contribute to the pathophysiology of CLL. The literature data evidence a spatiotemporal association between the cell surface expression of CD38 and that of other CLL antigens, such as the B-cell receptor (BCR), CD19, CD26, CD44, the integrin very late antigen 4 (VLA4), the chemokine receptor CXCR4, the vascular endothelial growth factor receptor-2 (VEGF-R2), and the neutrophil gelatinase-associated lipocalin receptor (NGAL-R). Most of these proteins contribute to CLL cell survival, proliferation and trafficking, and cooperate with CD38 in multilayered signal transduction processes. In general, these antigens have already been validated as therapeutic targets in cancer, and a broad repertoire of specific monoclonal antibodies and derivatives are available. Here, we review the state of the art in this field and examine the therapeutic opportunities for cotargeting CD38 and its partners in CLL, e.g. by designing novel bi-/trispecific antibodies.

Chronic Lymphocytic Leukemia B-Cell Normal Cellular Counterpart: Clues From a Functional Perspective

Chronic lymphocytic leukemia (CLL) is characterized by the clonal expansion of small mature-looking CD19+ CD23+ CD5+ B-cells that accumulate in the blood, bone marrow, and lymphoid organs. To date, no consensus has been reached concerning the normal cellular counterpart of CLL B-cells and several B-cell types have been proposed. CLL B-cells have remarkable phenotypic and gene expression profile homogeneity. In recent years, the molecular and cellular biology of CLL has been enriched by seminal insights that are leading to a better understanding of the natural history of the disease. Immunophenotypic and molecular approaches (including immunoglobulin heavy-chain variable gene mutational status, transcriptional and epigenetic profiling) comparing the normal B-cell subset and CLL B-cells provide some new insights into the normal cellular counterpart. Functional characteristics (including activation requirements and propensity for plasma cell differentiation) of CLL B-cells have now been investigated for 50 years. B-cell subsets differ substantially in terms of their functional features. Analysis of shared functional characteristics may reveal similarities between normal B-cell subsets and CLL B-cells, allowing speculative assignment of a normal cellular counterpart for CLL B-cells. In this review, we summarize current data regarding peripheral B-cell differentiation and human B-cell subsets and suggest possibilities for a normal cellular counterpart based on the functional characteristics of CLL B-cells. However, a definitive normal cellular counterpart cannot be attributed on the basis of the available data. We discuss the functional characteristics required for a cell to be logically considered to be the normal counterpart of CLL B-cells.

Prognosis biomarkers evaluation in chronic lymphocytic leukemia

OBJECTIVE/BACKGROUND

From clinical and biological points of view, chronic lymphocytic leukemia (CLL) is a heterogeneous disease characterized by a progressive accumulation of lymphocytes in the peripheral blood, bone marrow, and lymphoid organs. New prognostic markers in CLL may be useful to clinicians for predicting outcome and in clinical decision-making. The aim of this study was to evaluate the potential prognostic value of the apoptotic/survival-controlling proteins and protein tyrosine kinase ZAP-70 gene expression in CLL patients and control individuals, correlating such findings with patients' clinical data.

METHODS

Fifty-three patients diagnosed with CLL attending the hematology service of a clinical hospital, and 24 healthy individuals with no history of leukemia (Control group) were enrolled in this study. Analyses of apoptotic/survival-controlling proteins were performed by western blot and ZAP-70 gene expression was evaluated by real-time polymerase chain reaction.

RESULTS

Significant differences were observed for the p-p38, Mcl-1 long, and Mcl-1 short proteins when patients were compared with CLL and controls. A positive correlation between the results for Mcl-1 short and Mcl-1 long and lymphocyte count was observed, corroborating the hypothesis of an imbalance between proteins of cell survival pathways/apoptosis in CLL.

CONCLUSION

ZAP-70 gene expression was not detected as a discriminant biomarker in these CLL patients. An imbalance between apoptosis-related proteins was observed in the present study, corroborating the hypothesis of increased survival of lymphocytes in CLL patients.

Clinical and laboratory parameters that define clinically relevant B-CLL subgroups

B cell-type chronic lymphocytic leukemia (B-CLL) is a heterogeneous disease. This is reflected by the very wide-ranging clinical courses that B-CLL patients experience and by the marked variation in laboratory findings between patients. In this chapter, we will review the various clinical and laboratory parameters that divide B-CLL patients into "subgroups," and correlate the parameters that define them. When feasible, we will also link clinical features to the cellular and genetic characteristics recently defined for these leukemic cells. The discussion is limited to parameters that define phenotypes or subgroups that may relate to disease activity and clinical outcome.

Pan B-cell markers are not redundant in analysis of chronic lymphocytic leukemia (CLL)

BACKGROUND

The classic immunophenotype for chronic lymphocytic leukemia (CLL) is CD19(+), restricted dim surface expression of kappa or lambda light chain, CD5(+), CD23(+), dim CD20(+), negative FMC7, and negative CD79b. However, the necessity of assaying for all 3 pan B-cell markers (CD20, FMC7, and CD79b) by flow cytometry has not been definitively documented for CLL.

METHODS

Qualitative patterns and semi-quantitative assessment of staining intensity for CD20, FMC7 and CD79b were performed in 70 cases with a current or prior diagnosis of CLL or CLL with increased prolymphocytes leukemia (CLL/PL). The concurrent morphology in 66 of 70 specimens was classified as typical CLL in 53 cases, CLL/PL in 10 cases, and large cell lymphoma in 3 cases.

RESULTS

Forty percent of the cases varied from the characteristic immunophenotype by having moderate or bright staining of CD20 (36%), FMC7 (7%), and/or CD79b (18%). Discrepant qualitative staining patterns were found between FMC7 and CD20 (21%), CD20 and CD79b (15%), and CD79b and FMC7 (10%). Semiquantitative measurement of staining intensity showed little correlation between CD79b and CD20 or FMC7. Moderate correlation was seen between CD20 and FMC7. No correlation was observed between morphology and intensity of marker expression.

CONCLUSIONS

Variable patterns and intensity of staining were seen for FMC7, CD20, and CD79b in this cohort of CLL samples. Dim or negative staining was most consistently seen for FMC7 (93% of specimens). Although FMC7 staining intensity was moderately correlated with CD20, CD79b intensity was poorly correlated with either CD20 or FMC7, and thus, may provide some independent information.

Diagnostic role and prognostic significance of a simplified immunophenotypic classification of mature B cell chronic lymphoid leukemias

We verified the diagnostic and prognostic role of a simplified immunophenotypic classification (IC) in a series of 258 patients (M/F: 1.4; median age: 64 years; median follow-up: 64 months; 75 deaths) with mature B cell lymphoid leukemias (MBC-LL) for whom no histopathological diagnosis was available because of minimal or no lymph node involvement. The IC was based on the reactivity of three pivotal immunophenotypic markers: CD5, CD23 and SIg intensity. On the basis of different expression patterns, we identified four diagnostic clusters (C) characterized by distinct clinico-biological features and different prognoses: C1 (149 patients) identified most classical B cell chronic lymphocytic leukemias (CLL-type cluster; SIg(dim)/CD5+/CD23+); C2, 38 patients whose clinico-hematological characteristics were intermediate between C1 and C3 (CLL-variant cluster; SIg(bright)/CD5+/CD23+/-or SIg(dim)/CD5-/-/CD23 indifferent); C3 (16 patients) most situations consistent with mantle cell lymphoma in leukemic phase (MCL-type cluster; SIg(bright)/CD5+/CD23-); and C4, 55 cases, most of whom were consistent with leukemic phase lymphoplasmacytic/splenic marginal zone lymphomas (LP/S-type cluster; SIg(bright)/CD5-/+/CD23 indifferent). At univariate survival analysis, prognosis worsened from C1 to C4, C2 and C3 (P = 0.0001), and this was maintained at multivariate analysis (P = 0.006), together with CD11c expression (P = 0.0043), age at diagnosis (cut-off 70 years; P = 0.0008) and platelet count (cut-off 140 x 10(9)/l; P = 0.0034). Besides recognising the two well-known situations of classic B-CLL and MCL, our IC identified situations with distinct prognostic and/or clinical behaviors.

CD5 negative B-cell chronic lymphocytic leukemia: clinical and biological features of 42 cases

Chronic lymphocytic leukemia cell (CLL) usually (95%) express B-phenotype and the CD5 antigen which is usually present on the surface of normal T cells. However, among B CLL, 7 to 20% do not express CD5. The significance of the lack of CD5 expression remains unclear. We reviewed 42 consecutive CD5- B CLL seen in three French medical centers from 1985 to 1991 and compared them with 79 CD5+ B CLL. Immunophenotype studies were performed using indirect immunofluorescence under light microscopy as well as flow cytometry after 1988. B CLL was considered to be CD5 negative when less than 5% of mononuclear cells expressed CD5 after subtraction of the number of T-cells. Cases with CD5- B CLL had isolated splenomegaly more frequently (p = 2.10(-7)). They frequently expressed a higher level of surface immunoglobulin (S-Ig) or the switch mu/delta phenotype (p = 4.7 10(-2)). The median survival time was not reached but no significant difference between CD5 negative and positive B CLL was observed at the time of our data analysis (p = 0.97). Clinical presentation of CD5- B CLL seems to be different from other forms of B CLL. Although, no conclusion can be reached in terms of prognosis, CLL with low expression of CD5 should be regarded as a subtype of CLL with a different clinical presentation than CD5+ CLL.

Trisomy 12 in chronic lymphocytic leukemia--geographical variation

Incidence of trisomy 12 was studied in 60 cases of chronic lymphocytic leukemia (CLL) with chromosome 12 specific alpha-satellite DNA probe by fluorescence in situ hybridization (FISH). Trisomy 12 was observed in 37 (61.8%) patients. Cells with trisomy 12 were detected in a varying proportion, ranging from > 2% to 86%. Patients with trisomy 12 were predominantly observed with total white blood cell (WBC) count > 80 x 10(9) l(-1) (P < 0.001). In addition, the percentage of trisomy 12 positive lymphocytes correlated with the high WBC counts. Trisomy 12 was observed equally in typical and atypical CLL. 90% of our patients were in the intermediate and high risk groups. It was seen that there was significantly higher percentage of trisomy 12 positive lymphocytes ( > 10%) in the high risk groups (P < 0.05). A higher incidence of FMC7 positivity in atypical CLL was seen in our study. However, there was no significant relationship found between trisomy 12 positivity and expression of either FMC7 or CD23 in our cases. It appears that the CLL that we see at our centre is at a different phase of evolution and perhaps biologically different compared to the CLL seen in the West.

Clinical heterogeneity reflects biologic diversity in chronic lymphocytic leukemia

As the incidence of B cell chronic lymphocytic leukemia increases in an aging population, it becomes more important to re-evaluate our understanding of the disease process and current therapy. Previous treatment strategies have been, for the most part, unsuccessful in prolonging survival and thus new approaches are needed. More intense cellular and molecular research on the biologic diversity of this neoplasm will further our understanding of the causes of clinical heterogeneity and refine our ability to predict progression. New approaches, based on alterations of neoplastic cell growth by cytokines or chemotherapeutic agents, may enable clinicians to 'customize' individual treatments based on the stages of CLL B cell differentiation and our understanding of factors involved in the regulation of apoptosis and proliferation at those stages. Taken together, these efforts should ultimately yield much new information that will lead to reduced morbidity and mortality in B-CLL, the most common form of human leukemia.

Structure and function of VLA integrins: differential expression in B-cell leukemia/lymphoma

The integrin family of adhesion receptors includes at least 11 different alpha subunits and 6 different beta subunits which are associated to form 14 different alpha beta heterodimers, divided into three subfamilies. In particular, beta 1 subfamily integrins (VLA 1-6 proteins) have been found to mediate cell adhesion to extracellular matrix (ECM) component such as fibronectin, collagen, laminin; however, VLA-4 has been found to exhibit both cell-cell and cell-matrix adhesion functions. The reactivity of VLAs is virtually ubiquitous and independent of line or tissue specificity. However, the expression of individual VLAs within single tissues can be modulated according to the type or functional status of the cell. One of the main reasons for interest in these molecules is that they may play a determining role in neoplastic transformation and diffusion; in particular, in lymphoproliferative syndromes, a lack of cell adhesiveness or an abnormal adhesion pattern in neoplastic lymphocytes may free these cells from regulation, thus contributing towards the development of leukemia and/or lymphoma. Studies of VLA expression in B-cell leukemia/lymphomas show a modulation of VLA3 and VLA4 reactivity. The most interesting element is the identification of a VLA3/VLA4 pattern associated with B-cell chronic lymphocytic leukemia (B-CLL) characterised by a reduced expression of VLA4 and the constant expression of VLA3. Although the value of VLA3 as an additional marker for the diagnosis of classical B-CLL is indisputable, the biological/functional significance of this reactivity remains to be confirmed.

Human CD5-positive B cells in lymphoid malignancy and connective tissue diseases

The current literature on human CD5-positive B cells (CD5 + B cells) has been analysed, with a special emphasis on non organ-specific auto-immune diseases. Malignant cells of most of the chronic lymphoid leukaemias of the B cell lineage express the CD5 molecule. Antibodies of the IgM class produced by leukaemic B cells are multispecific auto-antibodies. The CD5 + B cell subset may be expanded in non organ-specific autoimmune diseases, such as rheumatoid arthritis, primary Sjögren's syndrome, systemic lupus erythematosus. This holds true for various conditions, including organ-specific auto-immune diseases. Since auto-immune features are common in lymphoproliferative disorders, and the latter be a complication in non organ-specific auto-immune diseases, CD5 + B cells may represent an intermediary between these auto-immune diseases and B cell lymphoproliferations. Studies on the regulation of CD5 + B cell production and function are likely to shed light on the aetiology of, and pathogenetic mechanisms operating in the different disease states.

Immunophenotyping of low-grade B-cell lymphoma in blood and bone marrow: poor correlation between immunophenotype and cytological/histological classification

Results of immunophenotypic examinations of peripheral blood and/or bone marrow (BM), involved in low-grade B-cell non-Hodgkin's lymphomas, were compared with the results of cytomorphological and histopathological examinations in 133 adult patients. 69 cases of chronic B-lymphocytic leukaemia (B-CLL), 16 centrocytic (CC) lymphomas, 14 centroblastic-centrocytic (CB/CC) lymphomas, 15 immunocytomas (IC), 10 cases of hairy cell leukaemia (HCL), four prolymphocytic leukaemias (PLL), two B-CLL in transformation, one splenic lymphoma with villous lymphocytes (SLVL), one hairy cell leukaemia variant (HCL-V), and one lymphocytic lymphoma (LC) were classified according to the Kiel and/or FAB classification. Leukaemic disease was found in 105 cases. The following markers were used for immunocytology (APAAP technique) of blood and/or BM smears: CD19, CD5, CD10, CD11c, CD14, CD21, CD22, CD23, CD25, CD38 and TdT. All cases tested showed CD19, but no TdT expression. Every case of HCL had a distinct phenotype with expression of CD11c, CD22 and CD25 and the lack of CD5 and CD23 antigens. In all other NHL cases a very heterogenous expression of CD-antigens with no significant correlations to the cytomorphological subtypes was found. The expression of CD5 is a frequent but inconstant finding in lymphoproliferative diseases other than B-CLL, so 50% of CB/CC, 75% of CC and 80% of IC were CD5 positive. Our results indicate that, with the exception of HCL, the diagnostic relevance of immunophenotyping for the classification of cytomorphologically and histopathologically defined subtypes in blood and/or BM is of very limited value.

Serum levels of helper factors (IL-1 alpha, IL-1 beta and IL-6), T-cell products (sCD4 and sCD8), sIL-2R and beta 2-microglobulin in patients with B-CLL and benign B lymphocytosis

Chronic B-lymphocytic leukemia (B-CLL) cells may be regulated by immune functions. In an attempt to analyze such functions, helper factors (IL-1 alpha, IL-1 beta and IL-6), T-cell products (sCD4 and sCD8) and sIL-2R and beta 2-microglobulin were measured in serum of patients at different stages of the disease. Patients were classified as having monoclonal lymphocytosis of undetermined significance (MLUS), stable or progressive B-CLL respectively. A significant, but modest, increase of IL-1 alpha was found in B-CLL as well as in MLUS patients whereas IL-6 levels were increased in MLUS only. sCD8 levels were increased both in MLUS and B-CLL but augmented sCD4 concentrations were found statistically significant only in progressive B-CLL. beta 2-microglobulin and sIL-2R were related to the extent of the monoclonal B-cell fraction. The data indicate an increased T-suppressor activity in both MLUS and B-CLL patients and a selective increase of helper T-cell activity in progressive B-CLL. A possible immunoregulatory influence of helper T cells on disease progression is discussed.

Immunophenotypic subclassification of chronic lymphocytic leukaemia (CLL)

To determine the significance of the immunophenotypic heterogeneity of B-cell chronic lymphocytic leukaemia (CLL), surface immunoglobulins (SIgs), mouse rosette assays (MR), and a panel of monoclonal antibodies for B cells, T cells and myeloid cells were performed on peripheral blood samples from 61 newly diagnosed cases. Four groups were observed: group I (SIg+, MR+, CD19/20+, CD5+, T antigen (Ag)-; 27 cases); group II (SIg+, MR+, CD19/20+, CD5+, T Ag+; 17 cases); group III (SIg+, MR+ CD19/20+, CD5-, T AG-; 12 cases); and group IV (SIg-, MR+, CD19/20+, Cd5+, T Ag-; 5 cases). Groups were compared according to French-American-British Cooperative Group subtypes, clinical and laboratory features, Rai staging, and survival. Typical CLL morphology (greater than 90% small lymphocytes) was present in 20/20 (100%) of group I cases and 23/27 (85%) group II, III and IV cases (P = 0.09). Expression of a myeloid antigen was seen in 5/27 group I cases (18%) and 1/16 group II cases (6%), but was not predictive of survival (P = 0.36). The CD5- group III had a lower haemoglobin level (P less than 0.0001), higher Rai stage (P less than 0.002), and poorer survival at 5 years (P less than 0.02) than the other groups. We conclude that at least four distinct immunophenotypic subgroups of B-cell CLL can be determined. Expression of myeloid or T-cell antigens does not appear to predict for patient survival; however, lack of CD5 antigen may be associated with more advanced stage of disease and poor patient survival.