tumor-engraftment-xenograft-mouse-model-human-mantle-cell

Tumor Engraftment in a Xenograft Mouse Model of Human Mantle Cell Lymphoma

B lymphocytes are key players in immune cell circulation and they mainly home to and reside in lymphoid organs. While normal B cells only proliferate when ...

simultaneous-study-recruitment-monocyte-subpopulations-under-flow

Simultaneous Study of the Recruitment of Monocyte Subpopulations Under Flow In Vitro

The recruitment of monocytes from the blood to targeted peripheral tissues is critical to the inflammatory process during tissue injury, tumor development ...

University Hospital, Geneva

University of Geneva

Idiopathic acquired sideroblastic anaemias (IASAs) form a subgroup of the myelodysplastic syndromes and are characterized by mitochondrial iron accumulation, bone marrow erythroid hyperplasia and decreased peripheral red blood cell counts. Increased intramedullary apoptosis of erythroid precursors is presumed to constitute the pathophysiological mechanism explaining this ineffective erythropoiesis, but if and how mitochondrial dysfunction is implicated in this process is currently unknown. We therefore studied bone marrow precursor cells obtained from nine patients with IASA for (i) caspase 3 activity, (ii) numbers of Annexin V- and 7-amino-actinomycin-positive cells, (iii) numbers of cells with diminished mitochondrial membrane potential, Delta Psi(m), and (iv) numbers of cells producing reactive oxygen species (ROS), and we compared the results with those of five normal bone marrow samples. Compared with controls, we found increased caspase 3 activity in all IASA samples, which correlated with increased numbers of Annexin-V-positive cells (r = 0.7). Analysis of different subpopulations showed increased apoptosis in erythroid populations compared with myeloid and/or lymphoid populations in five out of nine cases, and increased apoptosis in the last two populations in four out of nine cases. As evidence of mitochondrial dysfunction, Delta Psi(m) was found to be diminished in the erythroid subpopulations of all cases of IASA (66.6 +/- 17% vs. 34.6 +/- 12% in normals). Delta Psi(m) decrease was correlated to Annexin V positivity (r = 0.7). Astonishingly, no difference was found between IASA and normal bone marrows with regard to the number of ROS-producing cells. In fact, both groups exhibited a similar low proportion of ROS production (10.3 +/- 7% in normals vs. 6.8 +/- 5% in IASA). Taken together, our results show that mitochondria are clearly implicated in the apoptotic process in IASA patients. Whether this is a result of an intramitochondrial defect (e.g. Fe accumulation, secondary to mitochondrial or nuclear DNA mutations) or is secondary to an extracellular stimulus [e.g. tumour necrosis factor (TNF), Fas ligand (FasL)] remains to be determined.

Increased apoptosis in acquired sideroblastic anaemia.

Antigens of the Cromer blood group system reside on the glycoprotein CD55 (decay-accelerating factor). The Inab phenotype is the null phenotype of this system. So far, only five propositi have been described who exhibit this phenotype, and single-nucleotide substitutions in the CD55 gene have been found in three of them. This report describes the first example of a patient with an acquired and transient form of the Inab phenotype.

Acquired and transient RBC CD55 deficiency (Inab phenotype) and anti-IFC.

May-Hegglin anomaly (MHA), Fechtner syndrome (FTNS), Sebastian syndrome (SBS), and Epstein syndrome (EPS) are a group of rare, autosomal dominant disorders characterized by thrombocytopenia, giant platelets, and Döhle-like inclusion bodies, together with variable manifestations of Alport-like symptoms that include high-tone sensorineural deafness, cataracts, and nephritis. These disorders result from mutations in the MYH9 gene, which encodes for the nonmuscle myosin heavy chain A protein (also known as NMMHC-A). To date 20 different mutations have been characterized for this gene, but no clear phenotype-genotype correlation has been established, and very little is known regarding the molecular pathogenesis of this group of diseases. Here, we describe 2 new families with MHA/FTNS phenotypes that have been characterized in terms of their mutations, protein localization in megakaryocytes, protein expression, and mRNA stability. Our findings suggest that, at least for the Asp1424Asn mutation in the MYH9 gene, the phenotypes result from a highly unstable protein. No abnormalities in protein localization or mRNA stability were observed. We hypothesize that haploinsufficiency of the MYH9 results in a failure to properly reorganize the cytoskeleton in megakaryocytes as required for efficient platelet production.

Asp1424Asn MYH9 mutation results in an unstable protein responsible for the phenotypes in May-Hegglin anomaly/Fechtner syndrome.

We report on a case of cytomegalovirus (CMV) enterocolitis occurring in a 65-year-old patient after a first course of standard chemotherapy for a small cell lung carcinoma (SCLC). Colonic biopsies showed typical inclusion bodies, CMV IgM and IgG antibodies were found in the serum, and polymerase chain reaction for CMV-DNA was positive. Lymphopenia and diminished CD4 T-cell counts were observed. Diarrhoea ceased under ganciclovir treatment, the patient recovered, but died several months later of metastatic lung cancer. Significant immunosuppression leading to severe colitis by CMV infection or reactivation can occur after standard chemotherapy.

Cytomegalovirus colitis--a severe complication after standard chemotherapy.

Juvenile hereditary hemochromatosis is a genetically heterogeneous disorder transmitted as an autosomal recessive trait. It is most often caused by mutations in the HJV gene and rarely in the HAMP gene. Hepcidin is considered to constitute a negative regulator of iron absorption, and its production is increased in inflammatory states and iron overload. We report the detection of a new mutation in the HAMP gene leading to juvenile hemochromatosis in 2 members of a Portuguese family. The mutation lies in the 5'-UTR (untranslated region) of the gene and creates a new initiation codon in the context of a Kozak sequence. We found no trace of hepcidin protein in the patients' urine, suggesting that ribosomes select the mutant initiation codon for translation. The decrease of hepcidin production would thus lead to increased iron absorption, resulting in iron deposition in parenchymal tissues. Phlebotomy therapy of the 2 patients resulted in impressive clinical improvement.

Severe hemochromatosis in a Portuguese family associated with a new mutation in the 5'-UTR of the HAMP gene.

Sideroblastic anemias are a heterogenous group of disorders characterized by the presence of sideroblasts in the bone marrow aspirate. Current classification schemes distinguish between diseases of the heme synthesis pathway and diseases of other mitochondrial pathways which can either be of primary origin (defects in mitochondrial DNA) or of secondary origin (defects in nuclear DNA). Although several distinct hereditary forms exist, sideroblastic anemias are most frequently acquired diseases and belong to the group of myelodysplastic syndromes with the propensity to develop into overt leukemia. Treatment is mainly supportive (vitamins, blood transfusions, cytokines) and only rarely are bone marrow transplantations performed. The molecular defects of a few hereditary forms have already been elucidated, but the genes involved in the acquired forms are still largely unknown.

[Sideroblastic anemias].

Sideroblastic anemias (SA) are characterized by iron accumulation in the mitochondria of erythroblasts. Although we have evidence of mitochondrial gene alterations in sporadic congenital cases, the origin of acquired forms [refractory anemia with ring sideroblasts (RARS)], is still largely unknown. Here, we report the analysis of respiratory chain function in a patient with a large mitochondrial deletion and in patients with RARS. A young boy with SA showed symptoms typical of a mitochondrial disease with metabolic acidosis, muscle weakness and cerebral involvement. His bone marrow DNA was analyzed for the presence of mitochondrial deletions. We found a new mitochondrial (mt)DNA deletion spanning 3,614 bp and including all the mt genes encoding complex IV, plus ATPase 6 and 8, and several transfer (t)RNAs. All tissues analyzed (liver, skeletal muscle, brain, pancreas) showed a heteroplasmic distribution of this mutant DNA. Bone marrow homogenates were obtained from five patients with RARS and from three patients with normal bone marrow and respiratory chain function assayed by spectrophotometric analysis. Cytochrome c oxidase (CCO) activity was greatly reduced in the patient's bone marrow. In contrast, CCO activity and global respiratory chain function were conserved in patients with RARS. We conclude that deficient CCO activity secondary to mtDNA deletions is related to intramitochondrial iron accumulation, as in our patient or in those with Pearson's syndrome, whereas other mechanisms, e.g. nuclear DNA mutations, have to be proposed to be involved in the acquired forms of SA.

Different pathophysiological mechanisms of intramitochondrial iron accumulation in acquired and congenital sideroblastic anemia caused by mitochondrial DNA deletion.

Junctional adhesion molecule (JAM)-C is a member of the JAM family, expressed by a variety of different cell types, including human B lymphocytes and some B-cell lymphoma subtypes-in particular, mantle cell lymphoma (MCL). Treatment with anti-JAM-C pAbs reduces homing of human B cells to lymphoid organs in a NOD/SCID mouse model. In the present study, the role of JAM-C in the engraftment of human lymphoma B cells in mice was investigated. Administration of novel anti-JAM-C mAbs reduced tumor growth of JAM-CMCL cells in bone marrow, spleen, liver, and lymph nodes of mice. Treatment with anti-JAM-C antibodies significantly reduced the proliferation of JAM-C-expressing lymphoma B cells. Moreover, the binding of anti-JAM-C antibodies inhibited the phosphorylation of ERK1/2, without affecting other signaling pathways. The results identify for the first time the intracellular MAPK cascade as the JAM-C-driven signaling pathway in JAM-CB cells. Targeting JAM-C could constitute a new therapeutic strategy reducing lymphoma B-cell proliferation and their capacity to reach supportive lymphoid microenvironments.

Anti-JAM-C therapy eliminates tumor engraftment in a xenograft model of mantle cell lymphoma.

IL-6, a cytokine with broad functions in inflammation and immunity, has been extensively studied for its role on normal antibody-producing plasma cells. In addition, IL-6 is recognized as a proliferative factor for multiple myeloma (MM), a malignant plasma cell tumor developing in the bone marrow. Blocking IL-6 signaling was thus developed into a therapeutic approach for MM already early after its discovery, in 1991. Unfortunately, the first clinical trials did not demonstrate a clear benefit, but despite this apparent failure hopes on IL-6 antagonism are still high and trials ongoing. The cellular source of IL-6 has long been a matter of debate. IL-6 was first recognized as an autocrine factor produced by the malignant plasma cells themselves, but later reports clearly showed that IL-6 was a paracrine factor, produced by the microenvironment, mostly by cells from the myeloid lineage. Recently, we have confirmed that IL-6 originates from myeloid lineage cells, mainly from myeloid precursors. We have also demonstrated that IL-6 amplifies the pool of myeloid cells producing a second key factor for MM, a proliferation inducing ligand (APRIL). These findings form a new rationale for IL-6 inhibition in MM and for new ways to use IL-6 blocking in the clinics.

Revisiting IL-6 antagonism in multiple myeloma.

During hematopoiesis, the balance between proliferation, differentiation, and apoptosis is tightly regulated in order to maintain homeostasis. Failure in these processes can ultimately lead to uncontrolled proliferation and leukemia. Phosphatase and tensin homolog (PTEN) is one of the molecular pathways involved in this balance. By opposing PI3-kinases, PTEN inhibits proliferation and promotes differentiation and is thus considered a tumor suppressor. Indeed, PTEN is frequently mutated in many cancers, including leukemias. Loss of PTEN often leads to lymphoid cancers. However, little is known about the molecular events that regulate PTEN signaling during lymphopoiesis. In this study, we used zebrafish to address this. We report that N-myc downstream-regulated gene 1b (ndrg1b) rescues lymphoid differentiation after PTEN inhibition. We also show that a previously uncharacterized gene, fam49ab, inhibits T-cell differentiation, a phenotype that can be rescued by ndrg1b We propose that ndrg1b and fam49ab are 2 new modulators of PTEN signaling that control lymphoid differentiation in the zebrafish thymus.

Ndrg1b and fam49ab modulate the PTEN pathway to control T-cell lymphopoiesis in the zebrafish.

CD47, an ubiquitously expressed innate immune checkpoint receptor that serves as a universal "don't eat me" signal of phagocytosis, is often upregulated by hematologic and solid cancers to evade immune surveillance. Development of CD47-targeted modalities is hindered by the ubiquitous expression of the target, often leading to rapid drug elimination and hemotoxicity including anemia. To overcome such liabilities, we have developed a fully human bispecific antibody, NI-1701, designed to coengage CD47 and CD19 selectively on B cells. NI-1701 demonstrates favorable elimination kinetics with no deleterious effects seen on hematologic parameters following single or multiple administrations to nonhuman primates. Potent  and  activity is induced by NI-1701 to kill cancer cells across a plethora of B-cell malignancies and control tumor growth in xenograft mouse models. The mechanism affording maximal tumor growth inhibition by NI-1701 is dependent on the coengagement of CD47/CD19 on B cells inducing potent antibody-dependent cellular phagocytosis of the targeted cells. NI-1701-induced control of tumor growth in immunodeficient NOD/SCID mice was more effective than that achieved with the anti-CD20 targeted antibody, rituximab. Interestingly, a synergistic effect was seen when tumor-implanted mice were coadministered NI-1701 and rituximab leading to significantly improved tumor growth inhibition and regression in some animals. We describe herein, a novel bispecific antibody approach aimed at sensitizing B cells to become more readily phagocytosed and eliminated thus offering an alternative or adjunct therapeutic option to patients with B-cell malignancies refractory/resistant to anti-CD20-targeted therapy. .

Thomas Matthes

Hematology Service

University Hospital, Geneva

Tumor Engraftment in a Xenograft Mouse Model of Human Mantle Cell Lymphoma

Simultaneous Study of the Recruitment of Monocyte Subpopulations Under Flow In Vitro

Thomas Matthes

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Hematology Service

University Hospital, Geneva

Tumor Engraftment in a Xenograft Mouse Model of Human Mantle Cell Lymphoma

Simultaneous Study of the Recruitment of Monocyte Subpopulations Under Flow In Vitro

Hematology Service