Niche-expressed Galectin-1 is involved in pre-B acute lymphoblastic leukemia relapse through pre-B cell receptor activation.

B-cell acute lymphoblastic leukemia (B-ALL) reflects the malignant counterpart of developing B cells in the bone marrow (BM). Despite tremendous progress in B-ALL treatment, the overall survival of adults at diagnosis and patients at all ages after relapse remains poor. Galectin-1 (GAL1) expressed by BM supportive niches delivers proliferation signals to normal pre-B cells through interaction with the pre-B cell receptor (pre-BCR). Here, we asked whether GAL1 gives non-cell autonomous signals to pre-BCR+ pre-B ALL, in addition to cell-autonomous signals linked to genetic alterations. In syngeneic and patient-derived xenograft (PDX) murine models, murine and human pre-B ALL development is influenced by GAL1 produced by BM niches through pre-BCR-dependent signals, similarly to normal pre-B cells. Furthermore, targeting pre-BCR signaling together with cell-autonomous oncogenic pathways in pre-B ALL PDX improved treatment response. Our results show that non-cell autonomous signals transmitted by BM niches represent promising targets to improve B-ALL patient survival.

Modeling Heterogeneity of Triple-Negative Breast Cancer Uncovers a Novel Combinatorial Treatment Overcoming Primary Drug Resistance.

Triple-negative breast cancer (TNBC) is a highly aggressive breast cancer subtype characterized by a remarkable molecular heterogeneity. Currently, there are no effective druggable targets and advanced preclinical models of the human disease. Here, a unique mouse model (MMTV-R26Met mice) of mammary tumors driven by a subtle increase in the expression of the wild-type MET receptor is generated. MMTV-R26Met mice develop spontaneous, exclusive TNBC tumors, recapitulating primary resistance to treatment of patients. Proteomic profiling of MMTV-R26Met tumors and machine learning approach show that the model faithfully recapitulates intertumoral heterogeneity of human TNBC. Further signaling network analysis highlights potential druggable targets, of which cotargeting of WEE1 and BCL-XL synergistically kills TNBC cells and efficiently induces tumor regression. Mechanistically, BCL-XL inhibition exacerbates the dependency of TNBC cells on WEE1 function, leading to Histone H3 and phosphoS33RPA32 upregulation, RRM2 downregulation, cell cycle perturbation, mitotic catastrophe, and apoptosis. This study introduces a unique, powerful mouse model for studying TNBC formation and evolution, its heterogeneity, and for identifying efficient therapeutic targets.

GRASP55 Is Dispensable for Normal Hematopoiesis but Necessary for Myc-Dependent Leukemic Growth.

Grasp55 is a ubiquitous Golgi stacking protein involved in autophagy, protein trafficking, and glucose deprivation sensing. The function of Grasp55 in protein trafficking has been attributed to its PDZ-mediated interaction with the C-terminal PDZ-binding motifs of protein cargos. We have recently shown that such an interaction occurs between Grasp55 and the adhesion molecule Jam-C, which plays a central role in stemness maintenance of hematopoietic and spermatogenic cells. Accordingly, we have found that Grasp55-deficient mice suffer from spermatogenesis defects similar to Jam-C knockout mice. However, whether Grasp55 is involved in the maintenance of immunohematopoietic homeostasis through regulation of protein transport and Jam-C expression remains unknown. In this study, we show that Grasp55 deficiency does not affect hematopoietic stem cell differentiation, engraftment, or mobilization, which are known to depend on expression of Grasp55-dependent protein cargos. In contrast, using an Myc-dependent leukemic model addicted to autophagy, we show that knockdown of Grasp55 in leukemic cells reduces spleen and bone marrow tumor burden upon i.v. leukemic engraftment. This is not due to reduced homing of Grasp55-deficient cells to these organs but to increased spontaneous apoptosis of Grasp55-deficient leukemic cells correlated with increased sensitivity of the cells to glucose deprivation. These results show that Grasp55 plays a role in Myc-transformed hematopoietic cells but not in normal hematopoietic cells in vivo.

In vivo evaluation of safety, biodistribution and pharmacokinetics of laser-synthesized gold nanoparticles.

Capable of generating plasmonic and other effects, gold nanostructures can offer a variety of diagnostic and therapy functionalities for biomedical applications, but conventional chemically-synthesized Au nanomaterials cannot always match stringent requirements for toxicity levels and surface conditioning. Laser-synthesized Au nanoparticles (AuNP) present a viable alternative to chemical counterparts and can offer exceptional purity (no trace of contaminants) and unusual surface chemistry making possible direct conjugation with biocompatible polymers (dextran, polyethylene glycol). This work presents the first pharmacokinetics, biodistribution and safety study of laser-ablated dextran-coated AuNP (AuNPd) under intravenous administration in small animal model. Our data show that AuNPd are rapidly eliminated from the blood circulation and accumulated preferentially in liver and spleen, without inducing liver or kidney toxicity, as confirmed by the plasmatic ALAT and ASAT activities, and creatininemia values. Despite certain residual accumulation in tissues, we did not detect any sign of histological damage or inflammation in tissues, while IL-6 level confirmed the absence of any chronic inflammation. The safety of AuNPd was confirmed by healthy behavior of animals and the absence of acute and chronic toxicities in liver, spleen and kidneys. Our results demonstrate that laser-synthesized AuNP are safe for biological systems, which promises their successful biomedical applications.

Nidogen-1 Contributes to the Interaction Network Involved in Pro-B Cell Retention in the Peri-sinusoidal Hematopoietic Stem Cell Niche.

In the bone marrow, CXCL12 and IL-7 are essential for B cell differentiation, whereas hematopoietic stem cell (HSC) maintenance requires SCF and CXCL12. Peri-sinusoidal stromal (PSS) cells are the main source of IL-7, but their characterization as a pro-B cell niche remains limited. Here, we characterize pro-B cell supporting stromal cells and decipher the interaction network allowing pro-B cell retention. Preferential contacts are found between pro-B cells and PSS cells, which homogeneously express HSC and B cell niche genes. Furthermore, pro-B cells are frequently located in the vicinity of HSCs in the same niche. Using an interactome bioinformatics pipeline, we identify Nidogen-1 as essential for pro-B cell retention in the peri-sinusoidal niche as confirmed in Nidogen-1-/- mice. Finally, human pro-B cells and hematopoietic progenitors are observed close to similar IL-7+ stromal cells. Thus, a multispecific niche exists in mouse and human supporting both early progenitors and committed hematopoietic lineages.

Genetic, structural, and chemical insights into the dual function of GRASP55 in germ cell Golgi remodeling and JAM-C polarized localization during spermatogenesis.

Spermatogenesis is a dynamic process that is regulated by adhesive interactions between germ and Sertoli cells. Germ cells express the Junctional Adhesion Molecule-C (JAM-C, encoded by Jam3), which localizes to germ/Sertoli cell contacts. JAM-C is involved in germ cell polarity and acrosome formation. Using a proteomic approach, we demonstrated that JAM-C interacted with the Golgi reassembly stacking protein of 55 kDa (GRASP55, encoded by Gorasp2) in developing germ cells. Generation and study of Gorasp2-/- mice revealed that knock-out mice suffered from spermatogenesis defects. Acrosome formation and polarized localization of JAM-C in spermatids were altered in Gorasp2-/- mice. In addition, Golgi morphology of spermatocytes was disturbed in Gorasp2-/- mice. Crystal structures of GRASP55 in complex with JAM-C or JAM-B revealed that GRASP55 interacted via PDZ-mediated interactions with JAMs and induced a conformational change in GRASP55 with respect of its free conformation. An in silico pharmacophore approach identified a chemical compound called Graspin that inhibited PDZ-mediated interactions of GRASP55 with JAMs. Treatment of mice with Graspin hampered the polarized localization of JAM-C in spermatids, induced the premature release of spermatids and affected the Golgi morphology of meiotic spermatocytes.

For3D: Full organ reconstruction in 3D, an automatized tool for deciphering the complexity of lymphoid organs.

To decipher the complex topology of lymphoid structures, we developed an automated process called Full Organ Reconstruction in 3D (For3D). A dedicated image-processing pipeline is applied to entire collections of immunolabeled serial sections, acquired with a slide-scanning microscope. This method is automated, flexible and readily applicable in two days to frozen or paraffin-embedded organs stained by fluorescence or brightfield immunohistochemistry. 3D-reconstructed organs can be visualized, rotated and analyzed to quantify substructures of interest. Usefulness of For3D is exemplified here through topological analysis of several mouse lymphoid organs exhibiting a complex organization: (i) the thymus, composed of two compartments, a medulla intricately imbricated into a surrounding cortex, (ii) lymph nodes, also highly compartmentalized into cortex, paracortex and medulla and (iii) the vascularization of an EG7 primary thymoma. This open-source algorithm, based on ImageJ and Matlab scripts, offers a user-friendly interface and is widely applicable to any organ or tissue, hence readily adaptable to a broad range of biomedical samples.