The novel CXCR4 antagonist POL5551 mobilizes hematopoietic stem and progenitor cells with greater efficiency than Plerixafor

Mobilized blood has supplanted bone marrow (BM) as the primary source of hematopoietic stem cells for autologous and allogeneic stem cell transplantation. Pharmacologically enforced egress of hematopoietic stem cells from BM, or mobilization, has been achieved by directly or indirectly targeting the CXCL12/CXCR4 axis. Shortcomings of the standard mobilizing agent, granulocyte colony-stimulating factor (G-CSF), administered alone or in combination with the only approved CXCR4 antagonist, Plerixafor, continue to fuel the quest for new mobilizing agents. Using Protein Epitope Mimetics technology, a novel peptidic CXCR4 antagonist, POL5551, was developed. In vitro data presented herein indicate high affinity to and specificity for CXCR4. POL5551 exhibited rapid mobilization kinetics and unprecedented efficiency in C57BL/6 mice, exceeding that of Plerixafor and at higher doses also of G-CSF. POL5551-mobilized stem cells demonstrated adequate transplantation properties. In contrast to G-CSF, POL5551 did not induce major morphological changes in the BM of mice. Moreover, we provide evidence of direct POL5551 binding to hematopoietic stem and progenitor cells (HSPCs) in vivo, strengthening the hypothesis that CXCR4 antagonists mediate mobilization by direct targeting of HSPCs. In summary, POL5551 is a potent mobilizing agent for HSPCs in mice with promising therapeutic potential if these data can be orroborated in humans

Natalizumab affects T-cell phenotype in multiple sclerosis: implications for JCV reactivation

The anti-CD49d monoclonal antibody natalizumab is currently an effective therapy against the relapsing-remitting form of multiple sclerosis (RRMS). Natalizumab therapeutic efficacy is limited by the reactivation of the John Cunningham polyomavirus (JCV) and development of progressive multifocal leukoencephalopathy (PML). To correlate natalizumab-induced phenotypic modifications of peripheral blood T-lymphocytes with JCV reactivation, JCV-specific antibodies (serum), JCV-DNA (blood and urine), CD49d expression and relative abundance of peripheral blood T-lymphocyte subsets were longitudinally assessed in 26 natalizumab-treated RRMS patients. Statistical analyses were performed using GraphPad Prism and R. Natalizumab treatment reduced CD49d expression on memory and effector subsets of peripheral blood T-lymphocytes. Moreover, accumulation of peripheral blood CD8+ memory and effector cells was observed after 12 and 24 months of treatment. CD4+ and CD8+ T-lymphocyte immune-activation was increased after 24 months of treatment. Higher percentages of CD8+ effectors were observed in subjects with detectable JCV-DNA. Natalizumab reduces CD49d expression on CD8+ T-lymphocyte memory and effector subsets, limiting their migration to the central nervous system and determining their accumulation in peripheral blood. Impairment of central nervous system immune surveillance and reactivation of latent JCV, can explain the increased risk of PML development in natalizumab-treated RRMS subjects

MicroRNA-146a and AMD3100, two ways to control CXCR4 expression in acute myeloid leukemias

CXCR4 is a negative prognostic marker in acute myeloid leukemias (AMLs). Therefore, it is necessary to develop novel ways to inhibit CXCR4 expression in leukemia. AMD3100 is an inhibitor of CXCR4 currently used to mobilize cancer cells. CXCR4 is a target of microRNA (miR)-146a that may represent a new tool to inhibit CXCR4 expression. We then investigated CXCR4 regulation by miR-146a in primary AMLs and found an inverse correlation between miR-146a and CXCR4 protein expression levels in all AML subtypes. As the lowest miR-146a expression levels were observed in M5 AML, we analyzed the control of CXCR4 expression by miR-146a in normal and leukemic monocytic cells and showed that the regulatory miR-146a/CXCR4 pathway operates during monocytopoiesis, but is deregulated in AMLs. AMD3100 treatment and miR-146a overexpression were used to inhibit CXCR4 in leukemic cells. AMD3100 treatment induces the decrease of CXCR4 protein expression, associated with miR-146a increase, and increases sensitivity of leukemic blast cells to cytotoxic drugs, this effect being further enhanced by miR-146a overexpression. Altogether our data indicate that miR-146a and AMD3100, acting through different mechanism, downmodulate CXCR4 protein levels, impair leukemic cell proliferation and then may be used in combination with anti-leukemia drugs, for development of new therapeutic strategies

Evidence That a Lipolytic Enzyme—Hematopoietic-Specific Phospholipase C-β2—Promotes Mobilization of Hematopoietic Stem Cells by Decreasing Their Lipid Raft-Mediated Bone Marrow Retention and Increasing the Promobilizing Effects of Granulocytes

Hematopoietic stem/progenitor cells (HSPCs) reside in the bone marrow (BM) microenvironment and are retained there by the interaction of membrane lipid raft-associated receptors, such as the α-chemokine receptor CXCR4 and the α4β1-integrin (VLA-4, very late antigen 4 receptor) receptor, with their respective specific ligands, stromal-derived factor 1 and vascular cell adhesion molecule 1, expressed in BM stem cell niches. The integrity of the lipid rafts containing these receptors is maintained by the glycolipid glycosylphosphatidylinositol anchor (GPI-A). It has been reported that a cleavage fragment of the fifth component of the activated complement cascade, C5a, has an important role in mobilizing HSPCs into the peripheral blood (PB) by (i) inducing degranulation of BM-residing granulocytes and (ii) promoting their egress from the BM into the PB so that they permeabilize the endothelial barrier for subsequent egress of HSPCs. We report here that hematopoietic cell-specific phospholipase C-β2 (PLC-β2) has a crucial role in pharmacological mobilization of HSPCs. On the one hand, when released during degranulation of granulocytes, it digests GPI-A, thereby disrupting membrane lipid rafts and impairing retention of HSPCs in BM niches. On the other hand, it is an intracellular enzyme required for degranulation of granulocytes and their egress from BM. In support of this dual role, we demonstrate that PLC-β2-knockout mice are poor mobilizers and provide, for the first time, evidence for the involvement of this lipolytic enzyme in the mobilization of HSPCs

Endosymbiont DNA in Endobacteria-Free Filarial Nematodes Indicates Ancient Horizontal Genetic Transfer

Background: Wolbachia are among the most abundant symbiotic microbes on earth; they are present in about 66% of all insect species, some spiders, mites and crustaceans, and most filarial nematode species. Infected filarial nematodes, including many pathogens of medical and veterinary importance, depend on Wolbachia for proper development and survival. The mechanisms behind this interdependence are not understood. Interestingly, a minority of filarial species examined to date are naturally Wolbachia-free. Methodology/PrincipalFindings:We used 454 pyrosequencing to survey the genomes of two distantly related Wolbachia- free filarial species, Acanthocheilonema viteae and Onchocerca flexuosa. This screen identified 49 Wolbachia-like DNA sequences in A. viteae and 114 in O. flexuosa. qRT-PCR reactions detected expression of 30 Wolbachia-like sequences in A. viteae and 56 in O. flexuosa. Approximately half of these appear to be transcribed from pseudogenes. In situ hybridization showed that two of these pseudogene transcripts were specifically expressed in developing embryos and testes of both species. Conclusions/Significance: These results strongly suggest that the last common ancestor of extant filarial nematodes was infected with Wolbachia and that this former endosymbiont contributed to their genome evolution. Horizontally transferred Wolbachia DNA may explain the ability of some filarial species to live and reproduce without the endosymbiont while other species cannot

ErbB2 (HER2)-CAR-NK-92 cells for enhanced immunotherapy of metastatic fusion-driven alveolar rhabdomyosarcoma

IntroductionMetastatic rhabdomyosarcoma (RMS) is a challenging tumor entity that evades conventional treatments and endogenous antitumor immune responses, highlighting the need for novel therapeutic strategies. Applying chimeric antigen receptor (CAR) technology to natural killer (NK) cells may offer safe, effective, and affordable therapies that enhance cancer immune surveillance. MethodsHere, we assess the efficacy of clinically usable CAR-engineered NK cell line NK-92/5.28.z against ErbB2-positive RMS in vitro and in a metastatic xenograft mouse model.ResultsOur results show that NK-92/5.28.z cells effectively kill RMS cells in vitro and significantly prolong survival and inhibit tumor progression in mice. The persistence of NK-92/5.28.z cells at tumor sites demonstrates efficient antitumor response, which could help overcome current obstacles in the treatment of solid tumors.DiscussionThese findings encourage further development of NK-92/5.28.z cells as off-the-shelf immunotherapy for the treatment of metastatic RMS