CXCR4 and CD74 together enhance cell survival in response to macrophage migration-inhibitory factor in chronic lymphocytic leukemia.

Chronic lymphocytic leukemia (CLL) is characterized by the accumulation of small, mature CD5+ B lymphocytes in the blood, marrow, and lymphoid organs. Cell survival depends on interaction with the leukemic microenvironment. However, the mechanisms controlling CLL cell survival are still incompletely understood. Macrophage migration-inhibitory factor (MIF), a pro-inflammatory and immunoregulatory chemokine-like cytokine, interacts with CXCR4, a major chemokine receptor, as well as with CD74/invariant chain, a single-pass type II receptor. In this study, we analyzed the roles of CXCR4, CD74, and MIF in CLL. Mononuclear cells from patients with hematological malignancies were analyzed for coexpression of CXCR4 and CD74 by flow cytometry. Strong co- and overexpression of CXCR4 and CD74 were observed on B cells of CLL patients (n = 10). Survival and chemotaxis assays indicated that CXCR4 and CD74 work together to enhance the survival and migration of malignant cells in CLL. Blockade of the receptors, either individually or in combination, promoted cell death and led to an abrogation of MIF-driven migration responses in murine and human CLL cells, suggesting that joint activation of both receptors is crucial for CLL cell survival and mobility. These findings indicate that the MIF/CXCR4/CD74 axis represents a novel therapeutic target in CLL.

Longitudinal changes in telomere length in PCB-exposed individuals: interaction with CMV infection.

We recently demonstrated a significant shortening of age-adapted telomere length (TL) in lymphocytes of polychlorinated biphenyls (PCB)-exposed individuals. Here, we analyzed TL in individuals of the same PCB-exposed cohort during a 6-year follow-up period, investigating the change in TL between the first and second measurement as a function of time, concentration of PCBs and cytomegalovirus (CMV) infection. The age-adjusted TL of lymphocytes within the cohort of PCB-exposed individuals recovered from a first assessment in 2011 to a second assessment in 2017. Remarkably, if the concentration of lower chlorinated PCBs (LC PCBs) in 2011 was high (≥ 0.055 µg/L), the TL of CMV seropositive individuals remained significantly shortened both compared to age-adjusted controls as well as intra individually. This was confirmed by analysis of covariance as well as by multivariate linear mixed effects models. Since telomeres are responsive to various stress response pathways, including viral infection, we conclude that PCBs could contribute to immune senescence-like phenotypes associated with CMV infections and exacerbate negative aspects associated with the aging of the immune system.

Accelerated telomere shortening in peripheral blood lymphocytes after occupational polychlorinated biphenyls exposure.

Polychlorinated biphenyls (PCBs) are organochlorine pollutants with a worldwide dissemination. We examined telomere length (TL) in peripheral blood cells of 207 individuals with a high body burden of PCBs due to occupational exposure in a transformer recycling company. Whereas TL in granulocytes was not affected, the age-adjusted TL in lymphocytes (∆TLLymph) of exposed individuals was significantly shorter than expected [-0.77 kb; 95 % confidence interval (CI) -0.9316; -0.6052; p = 0.0001]. PCB exposure did not affect lymphocyte numbers or T cell receptor excision circle (TREC) levels in T cells, suggesting that PCBs cause loss of telomeric DNA in T cells due to their metabolic activation and antigen-stimulated proliferation. In support of this hypothesis, blood plasma levels of PCB-exposed individuals inhibited expression of telomerase, the telomere elongating enzyme in vitro in antigen-specific T cell proliferation assays. 3-OH-CB28, a downstream metabolite of the lower chlorinated PCB-28 in PCB-exposed individuals (mean blood plasma concentration: 0.185 ± 0.68 ng/mL), inhibited telomerase gene expression within 48 h of incubation in lymphoproliferative assays starting at a concentration of 0.27-6.75 µg/mL and accelerated telomere shortening in long-term cell culture experiments. Accelerated telomere shortening due to PCB exposure may lead to limitations of cell renewal and clonal expansion of lymphocyte populations. As PCB-related immune dysfunctions have been linked to increased susceptibility to infectious diseases and increased risk of cancer, our data provide a possible explanation, for how PCBs could promote infections and cancer through limiting immune surveillance.

Telomere dynamics in patients with del (5q) MDS before and under treatment with lenalidomide.

Myelodysplastic syndrome (MDS) associated with an acquired, isolated deletion of chromosome 5q (del (5q) MDS), represent a clonal disorder of hematopoiesis and a clinically distinct entity of MDS. Treatment of del (5q) MDS with the drug lenalidomide has significantly improved quality of life leading to transfusion independence and complete cytogenetic response rates (CCR) in the majority of patients. Telomeres are located at the end of eukaryotic chromosomes and are linked to replicative history/potential as well as genetic (in) stability of hematopoietic stem cells. Here, we analyzed telomere length (TL) dynamics before and under lenalidomide treatment in the peripheral blood and/or bone marrow of del (5q) patients enrolled in the LEMON-5 study (NCT01081431). Hematopoietic cells from del (5q) MDS patients were characterized by significantly shortened TL compared to age-matched healthy controls. Telomere loss was more accelerated in patients with longer disease duration (>2 years) and more pronounced cytopenias. Sequential analysis under lenalidomide treatment revealed that previously shortened TL in peripheral blood cells was significantly "elongated" towards normal levels within the first six months suggesting a shift from clonal del (5q) cells towards normal hematopoiesis in lenalidomide treated MDS patients. Taken together our findings suggest that the development of the del (5q) clone is associated with accelerated telomere shortening at diagnosis. However, upon induction of CCR and reoccurrence of normal hematopoiesis, the lack of a persistent TL deficit argues against telomere-mediated genetic instability neither as a disease-promoting event of del (5q) MDS nor for lenalidomide mediated development of secondary primary malignancies of the hematopoietic system in responding patients.

Cup-like blasts in acute myeloid leukemia.

A patient with AML with normal karyotype and the cytological pattern of cup-like blasts (CLB) is reported. The typical morphology on Pappenheim stained blood smears is shown. In addition transmission electron microscopy pictures demonstrate impressively the invaginated nuclear pocket compressing the chromatin. Cup-like blasts usually do not express CD34. There is a close relationship of CLB-AML with the molecular aberrations of NPM1 and/or FLT3-ITD.

Telomere elongation and clinical response to androgen treatment in a patient with aplastic anemia and a heterozygous hTERT gene mutation.

Telomere length (TL) both reflects and limits the replicative life span of normal somatic cells. As a consequence, critically shortened telomeres are associated with a variety of disease states. Telomere attrition can be counteracted by a nucleoprotein complex containing telomerase. Mutations in subunits of telomerase, telomerase-binding proteins as well as in members of the shelterin complex have been described both in inherited and acquired bone marrow failure syndromes. Here, we report on a patient with acquired aplastic anemia and a nonsynonymous variation of codon 1062 of the hTERT gene (p.Ala1062Thr) whose substantial and maintained hematologic response to long-term androgen treatment (including complete transfusion independence) was paralleled by a significant and continued increase in TL in multilineage peripheral blood cells. To our knowledge, this represents the first case of sustained telomere elongation in hematopoietic stem cells induced by a pharmacological approach in vivo (141 words).