Ornella Lovato

The TNF-Family Cytokine TL1A Inhibits Proliferation of Human Activated B Cells

Death receptor (DR3) 3 is a member of the TNFR superfamily. Its ligand is TNF-like ligand 1A (TL1A), a member of the TNF superfamily. TL1A/DR3 interactions have been reported to modulate the functions of T cells, NK, and NKT cells and play a crucial role in driving inflammatory processes in several T-cell-dependent autoimmune diseases. However, TL1A expression and effects on B cells remain largely unknown. In this study, we described for the first time that B cells from human blood express significant amounts of DR3 in response to B cell receptor polyclonal stimulation. The relevance of these results has been confirmed by immunofluorescence analysis in tonsil and spleen tissue specimens, which showed the in situ expression of DR3 in antigen-stimulated B cells in vivo. Remarkably, we demonstrated that TL1A reduces B-cell proliferation induced by anti-IgM-antibodies and IL-2 but did not affect B-cell survival, suggesting that TL1A inhibits the signal(s) important for B-cell proliferation. These results revealed a novel function of TL1A in modulating B-cell proliferation in vitro and suggest that TL1A may contribute to homeostasis of effector B-cell functions in immune response and host defense, thus supporting the role of the TL1A/DR3 functional axis in modulating the adaptive immune response.

Low catalase expression confers redox hypersensitivity and identifies an indolent clinical behavior in CLL

B-cell receptor (BCR) signaling is a key determinant of variable clinical behavior and a target for therapeutic interventions in chronic lymphocytic leukemia (CLL). Endogenously produced H2O2 is thought to fine-tune the BCR signaling by reversibly inhibiting phosphatases. However, little is known about how CLL cells sense and respond to such redox cues and what effect they have on CLL. We characterized the response of BCR signaling proteins to exogenous H2O2 in cells from patients with CLL, using phosphospecific flow cytometry. Exogenous H2O2 in the absence of BCR engagement induced a signaling response of BCR proteins that was higher in CLL with favorable prognostic parameters and an indolent clinical course. We identified low catalase expression as a possible mechanism accounting for redox signaling hypersensitivity. Decreased catalase could cause an escalated accumulation of exogenous H2O2 in leukemic cells with a consequent greater inhibition of phosphatases and an increase of redox signaling sensitivity. Moreover, lower levels of catalase were significantly associated with a slower progression of the disease. In leukemic cells characterized by redox hypersensitivity, we also documented an elevated accumulation of ROS and an increased mitochondrial amount. Taken together, our data identified redox sensitivity and metabolic profiles that are linked to differential clinical behavior in CLL. This study advances our understanding of the redox and signaling heterogeneity of CLL and provides the rationale for the development of therapies targeting redox pathways in CLL.

Integration of B-cell receptor-induced ERK1/2 phosphorylation and mutations of SF3B1 gene refines prognosis in treatment naive chronic lymphocytic leukemia.

Signaling events downstream of the B-cell receptor (BCR) are key determinants of the clinical behavior of chronic lymphocytic leukemia (CLL).[1][1],[2][2] Extracellular signal-regulated kinase 1/2 (ERK1/2) is a major pathway downstream of BCR stimulation.[3][3],[4][4] In a recent study, applying a

Expression and function of the TL1A/DR3 axis in chronic lymphocytic leukemia

TNF-like ligand 1A (TL1A) and its unique receptor death receptor 3 (DR3) acts as broad T-cell costimulator involved in regulatory mechanisms of adaptive immune response under physiological and pathological settings. Moreover, we have recently shown that TL1A negatively regulates B-cell proliferation. Despite increasing interest on the TL1A/DR3-axis functions, very little is known on its expression and role in leukemia. In this study, we investigated the expression and function of TL1A/DR3 axis in chronic lymphocytic leukemia (CLL). DR3 was differentially expressed in activated CLL cells and predominantly detected in patients with early clinical stage disease. Soluble TL1A has been revealed in the sera of CLL patients where higher TL1A levels were associated with early stage disease. T cells, monocytes and leukemic B cells have been identified as major sources of TL1A in CLL. The relevance of these findings has been sustained by functional data showing that exogenous TL1A reduces CLL proliferation induced by stimulation of the B cell receptor. Overall, these data document the expression of the TL1A/DR3 axis in early-stage CLL. They also identify a novel function for TL1A as a negative regulator of leukemic cell proliferation that may influence the CLL physiopathology and clinical outcome at an early-stage disease.

35 BCR-signaling profiles associated with prognosis and progression in B-CLL

Background. B-cell chronic lymphocytic leukemia (B-CLL) patients exhibit a variable clinical course. Several biological parameters have been shown to be associated with clinical outcome in CLL. Among them, the most reliable markers are represented by the absence of somatic mutations within the immunoglobulin variable heavy chain genes (IGHV), the expression of CD38 antigen, or the presence of the ZAP-70 tyrosine kinase. These parameters of poor clinical outcome are structurally and/or functionally linked to B-cell Receptor (BCR) expressed by CLL cells, thereby strengthening the hypothesis that antigenic stimulation mediated by the BCR represents a driving event in the onset and progression of the malignant B cells. Methods. We applied a “network level” analysis of BCR signaling by measuring single-cell profiles of phosphoprotein networks by flow cytometry. We evaluated the response to BCR engagement in primary cells isolated from 27 CLL patients by analyzing the phosphorylation states of 5 phosphoproteins on the route of BCR signaling, including p-Syk, p-NF-kappaB, p-Erk1/2, p-p38 and p-JNK. BCR was cross-linked by incubating cells with anti-IgM antibodies. Results. Unsupervised clustering analysis distinguished BCR response profiles of phosphoproteins that differentiated cases of CLL with mutated IGHV from those with unmutated IGHV (P=0.0003), cases with low levels of CD38 expression from those with high levels (P=0.0004) and cases with ZAP-70negative leukemic cells from cases that were ZAP-70-positive (P=0.001). Furthermore, the same BCR response profiles were also associated with time to progression (P=0.0014) and with overall survival (P=0.049), as assessed by Kaplan–Meier curves and the log-rank test. Independent survival analysis of time to progression via fitting Cox proportional hazards models comprising clinical covariates and/or BCR network response to modulation demonstrated that measuring modulated BCR network signaling can yield improved prognostic information compared to CD38 status alone (likelihood ratio test 5.8 for CD38 versus 10.6 for signaling) and enhance prognostic assessment using IGHV status (likelihood ratio test for IGHV = 14.8 versus for IGHV + signaling = 17.9).