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[Evidence of urinary glomerular basement membrane (GBM) antigens excretion in 3 rodents (rat, mouse, and guinea-pig) (author's transl)].

Immunodiffusion technique, with rabbits antibodies against rat glomerular basement membrane (GBM), permits to evidence the presence of GBM antigens into normal urines of 3 rodents (rat, mouse, and guinea-pig). These results confirm the earlier works in human and rabbit urines and show the antigenic communauty existing between the 3 rodents GBM, since we can evidence antigens of 3 different mammals with the same antibody. The origin and the nature of this patterns and the signification of this presence into mammalian urines are discussed.

Animals

Plasma protein handling in the rat kidney: micropuncture experiments in the acute heterologous phase of anti-GBM-nephritis.

Glomerular filtration and tubular uptake of plasma proteins have been studied in the rat using micropuncture techniques. 1. Under control conditions the glomerular capillary wall is an effective barrier, only 7.6 microgram/min x 100 g BW albumin have been measured as filtered load. Four to twelve hours after i.v. injection of anti-glomerular-basement membrane serum (anti-GBM-serum sieving coefficient phi and filtered load increased in a dose-dependent manner (phi albumin in controls = 0.27 x 10(-3), after injection of 0.5 ml Antiserum phi = 0.28 x 10(-3) and 1.0 ml Antiserum phi = 2.32 x 10(-3)). 2. The tubular reabsorption capacity is almost reached under control conditions and amounts to 5.6--10.7 microgram/min x 100 g BW for albumin. Only reduced GFR (0.36 +/- 0.07 ml/min x 100 g BW) and reduced tubular flow lead to increased tubular uptake under overload conditions (10.7 vs. 99.0 microgram albumin/min x 100 g BW). 3. Tubular reabsorption of so-called high-molecular-weight proteins seems to be a nonselective mechanism. The ratio Alb/Alb + Glob (89.9--93.1%) did not differ significantly at the individual puncture sites and in the final urine.

Animals

Nephrotic syndrome in anti-GBM antibody mediated glomerulonephritis.

Glomerulonephritis induced by antibodies to the glomerular basement membrane is a well recognized cause of renal disease and is responsible for 5% to 15% of all glomerular disease. The patients usually present with an acute nephritic syndrome followed by rapidly progressive renal failure. We report two patients who presented with the nephrotic syndrome and anti-GBM glomerulonephritis, and who exhibited differing clinical courses not characteristic of "rapidly progressive glomerulonephritis" or Goodpasture's syndrome.

Adult

Evidence of both anti-GBM and immune complex mediated pathogenesis in the initial phase of Goodpasture's syndrome.

A 19 year old women presented with pulmonary hemorrhage, rapidly progressive glomerulonephritis and antiglomerular basement membrane antibody in her serum. In the initial phase of the disease a double layered linear deposit of IgG was seen on the glomerular capillary basement membrane together with a finely granular or focal and lumpy single layer deposit of C3 and numerous small subepithelial electron dense deposits. These findings are suggestive of the simultaneous occurrence of anti-GBM and immune complex glomerulonephritis.

Adult

Glomerular basement membrane: biosynthesis and chemical composition in the streptozotocin diabetic rat.

To study the effect of streptozotocin induced diabetes on glomerular basement membrane (GBM) synthesis, an isolated rat glomerular preparation has been developed, and its metabolic properties have been defined. The chemical composition of normal rat GBM isolated from this preparation closely resembles human GBM. Incubation with [U-14C] lysine leads to prompt incorporation of label into GBM and the subsequent appearance of labeled hydroxylysine. A 1-h lag before detection of labeled hydroxylysine in GBM suggests a delay in the release of GBM precursors. Significantly lower counts appeared in the nondialyzable fraction of the medium than in insoluble GBM during pulse-chase experiments, and labeled hydroxylysine accounted for a lower portion of the total counts in the medium (0.85%) than in the GBM (1.98%). Isolated glomeruli were prepared from streptozotocin diabetic rats of 4-6 wks duration. After incubation with [ U-14C] lysine recovery of label in diabetic GBM (88.98+/-8.26 nmol/g GBM) did not differ from age matched controls (82.52 +/- 8.26 nmol/g GBM). In pulse-chase experiments recovery of label in hydroxylysine of diabetic GBM (o.473 +/- 0.082 nmol/g GBM) did not differ from age matched controls (0567+/-0.065 nmol/g GBM). These findings indicate normal rates of GBM synthesis and hydroxylation of lysine residues in animals with streptozotocin diabetes.

Amino Acids

High affinity binding of 125I-angiotensin II to rat glomerular basement membranes.

125I-angiotensin II (AII) specifically bound to rat glomerular basement membrane (GBM). The kinetics of binding were similar to those obtained with the total glomeruli. The apparent dissociation constant was close to 50 pM with both preparations. The number of sites related to the amount of protein was two times greater with GBM than with total glomeruli. Since the amount of GBM protein extracted from a given amount of glomerular protein was about 10%, it was possible to estimate the share of the GBM binding sites for AII as representing 20% of the total number present in the entire glomerulus. Binding studies at equilibrium as a function of 125I-AII concentration and competitive binding experiments suggested either multiplicity of the binding sites or cooperativity in the binding reaction. Degradation of 125I-AII in the presence of GBM was slight and did not increase with time. The difference in the degrees of degradation of 125I-AII was too small to account for the observed difference in binding when the results obtained with GBM and isolated glomeruli preparations were compared. 125I-AII binding to GBM was increased after treatment of these membranes with collagenase, slightly diminished with neuraminidase, and almost completely abolished with trypsin suggesting the proteic nature of the receptor. 125I-AII binding to GBM was diminished after incubation of GBM with anti-GBM antibodies as a result of a decrease in the number of binding sites. 125I-AII binding was even more diminished in preparations of glomeruli isolated from rats passively immunized with anti-GBM antibodies when compared with glomeruli from control animals. This resulted from both smaller affinity for AII and decrease in the number of the binding sites. The present data provides evidence for specific binding sites for AII localized on GBM. This is noteworthy since receptors for polypeptide hormones are currently observed on the surface of cell membranes. These findings also suggest a new physiological role for AII which might involve modification of GBM permeability.

Angiotensin II

Immunochemical characterization and quantitation of the human glomerular basement membrane antigen from the urine of patients with glomerular diseases.

A soluble glomerular basement membrane (GBM) antigen was detected in the urines of patients with various glomerular diseases including chronic glomerulonephritis, nephrotic syndrome, chronic renal insufficiency, and lupus nephropathy. The urinary GBM antigen (u-GBM) was immunochemically distinct from other renal antigens and other serum components, but it was cross-reactive with trypsinized human GBM antigen (t-GBM). The molecular size of u-GBM was approximately the same as human serum albumin as estimated by elution patterns on Sephadex G-200. The concentration of u-GBM was estimated quantitatively by a single radial radioimmunodiffusion. Although differed from case to case, a rough correlation with the type and/or stage of nephrotic syndrom existed. It was also demonstrated that the amounts of u-GBM decreased in response to steroid therapy of nephrotic syndrome. It was further shown that in a case of membranoproliferative glomerulonephritis, anti-GBM antibody could be eluted from the kidney removed from the patient. These findings imply that the GBM antigen plays an important role in the pathogenesis of human renal diseases. The pathophysiological significance of urinary GBM excretion in renal diseases is also discussed here.

Antigens

Spatial orientation and distribution of antigens within human glomerular basement membrane.

Antibodies to GBM have a linear staining pattern along the GBM by immunofluorescence. In this study, we have examined the distribution of human GBM antigens using Goodpasture antibody and heterologous rabbit anti-human GBM antibody. Goodpasture sera and Goodpasture antibody eluted from diseased kidneys reacted as a single linear component within the GBM. Rabbit anti-human GBM was shown to react along distinctly separate zones of the inner and outer aspects of the GBM; the central portion of the GBM seemed to be nonreactive with this antibody. In comparison, Goodpasture antibodies reacted along the inner zone of the GBM but at a locus external to that reacting with heterologous rabbit anti-GBM antibody. These observations of linear binding of antibody to different sites along the GBM suggest a spatial organization of antigen not previously observed.

Anti-Glomerular Basement Membrane Disease

Infectious bursal disease virus (IBDV) as a novel oncolytic virotherapy in glioblastoma.

BACKGROUND: Glioblastoma (GBM) is the most aggressive form of cancer of the central nervous system. Despite advances in immunotherapies and standard-of-care treatments for GBMs, clinical outcomes remain limited-owing to the immunosuppressive tumor microenvironment and the intrinsic resistance of GBM to conventional approaches. As a result, there is growing interest in rational combination strategies, particularly those pairing oncolytic viruses with immune-based therapies or established treatment modalities. Oncolytic viruses, by displaying conditionally enabled tumor cell-restricted replication, while stimulating antitumor immune responses and leaving healthy tissue unharmed, have the potential to reshape the therapeutic landscape in GBM and aid in achieving more durable benefits for patients. This study investigates the use of infectious bursal disease virus (IBDV) as a potential virotherapy for GBM. METHODS AND RESULTS: In vitro, IBDV infects and replicates within murine GBM cells and patient-derived GBM stem cells, inducing direct oncolysis and activating proinflammatory gene expression programs. IBDV also enhances the cytolytic activity of temozolomide (TMZ) in treated GBM cells, complementing TMZ chemotherapeutic activity. In vivo, treatment with IBDV in CT-2A GBM-bearing syngeneic mice significantly reduced tumor growth and improved survival compared with control mice. Intratumoral administration of IBDV induces a deep remodeling of the tumor immune microenvironment, reducing immunosuppressive M2-like macrophages and increasing the ratio of CD8+T cells to regulatory T cells. This reversion of immunosuppression linked to monocyte-derived macrophages has been confirmed on experimental ex vivo infections of explants derived from human GBM donors. CONCLUSION: These findings support further consideration of IBDV as a novel virotherapeutic agent for GBM.

Oncolytic Virotherapy

Efficacy of MET-targeting CAR T cells against glioblastoma patient-derived xenograft models.

BACKGROUND: Genetic alteration of the MET receptor tyrosine kinase frequently occurs in glioblastoma (GBM). Clinically, bevacizumab treatment results in MET signaling activation, leading to GBM recurrence with a more malignant phenotype. While MET has been a promising therapeutic target, MET inhibitors have not been successful in treating GBM patients. MET-directed chimeric antigen receptor (CAR) T cells hold the promise of targeting MET-positive GBM regardless of genetic alterations or kinase activity. METHODS: GBM patient-derived xenografts (PDX) harboring MET amplification (METamp) or PTPRZ-MET fusion (ZM) were propagated in vivo followed by glioma stem cell (GSC) isolation. Cell-based assays were used for comparing GSC survival in response to MET inhibitors and CAR T cells. Multi-panel cytokine release was analyzed to profile MET-CAR T cell activation during co-culture with GBM. Orthotopic tumor growth and real-time imaging were performed to evaluate MET-CAR T cell therapeutic efficacy in vivo. RESULTS: Although GBM are heterogeneous tumors, neuro-sphere cells isolated from METamp or ZM fusion PDX tumors showed universal cognate genetic MET alteration along with GSC markers such as SOX2 and nestin. Both METamp and ZM fusion tumors showed MET overexpression but only the METamp cells presented activated MET signaling which was vulnerable to MET inhibitors. In contrast, MET-CAR T cells specifically inhibited all MET-positive tumor growth regardless of MET activation status. CONCLUSIONS: Whereas MET inhibitors are effective in MET-active tumors, MET-CAR T cells eradicate MET-positive GBM growth in an antigen-dependent manner, demonstrating a promising therapeutic approach for treating MET-positive GBM. MET overexpression, especially METamp and ZM fusion may be used to predefine the GBM patients for treating with MET-CAR T cell therapy.

Glioblastoma

Induction of autoimmunity to antigens of the glomerular basement membrane in inbred Brown-Norway rats.

Induction of autoimmune antibodies against antigens of glomerular basement membrane (GBM) was studied in nine inbred strains of rats each with a different major histocompatibility complex H-1. Brown-Norway (BN) (H-1n), Lewis (H-1(1)), PVG/c (H-1c), AS2 (H-1f), AVN (H-1a), BD V (H-1d), DA (H-1a) and F344 (H-1(1)) rats were immunized with bovine GBM and Freund's complete adjuvent (CFA). A pronounced linear deposition of host IgG (IgG1 and IgG2a) along the GBM was found in BN rats. No deposition of C3 could be detected in the glomeruli nor did the animals develop proteinuria. The quantity of autoimmune antibodies fixed to the GBM was low (48 microgram +/- 14) which could explain the absence of C3 deposition and proteinuria. The antigenic specificity of the antibodies deposited along the GBM in BN rats was shown by the fixation in vitro of the eluted antibodies to the GBM and tubular basement membrane (TBM) of normal kidneys. A much weaker and irregular deposition of host IgG along the GBM was observed in PVG/c, AS2. AVN, BD V, DA and F344 rats. Of these strains, eluates from the glomeruli of PVG/c, AVN, BD V and DA rats fixed very weakly to the GBM of normal kidneys whereas eluates from AS2 and F344 rats did not fix to GBM or TBM. No deposition of host IgG was found in Lewis rats, and the eluates did not fix to normal kidneys. Congenic L.BN rats with the BN H-1n haplotype and a Lewis background did not respond. This study shows a genetic predisposition in rats to an autoimmune anti-GBM response which is not, or not exclusively, controlled by genes linked to the H-1 histo-compatibility complex.

Animals

Circadian variation in MGMT promoter methylation and expression predicts sensitivity to temozolomide in glioblastoma.

PURPOSE: Recent studies show that glioblastoma (GBM) is more sensitive to temozolomide (TMZ) in the morning. In cells, inhibiting O6-Methylguanine-DNA-Methyltransferase (MGMT) abolished time-dependent TMZ efficacy, suggesting that circadian regulation of this DNA repair enzyme underlies daily TMZ sensitivity. Here, we tested the hypotheses that MGMT promoter methylation and protein abundance vary with time-of-day in GBM, resulting in daily rhythms in TMZ efficacy. METHODS: We assessed daily rhythms in MGMT promoter methylation in GBM in vitro and retrospectively analyzed MGMT methylation status in human GBM biopsies collected at different times of day. Next, we measured MGMT and BMAL1 protein abundances in GBM cells collected at four-hour intervals. To understand the therapeutic implications of circadian variations in MGMT, we incorporated its daily rhythms into an in vitro mathematical model capturing interactions between MGMT, TMZ, and GBM DNA. RESULTS: We found daily rhythms in MGMT promoter methylation and protein levels in GBM in vitro, and in patient biopsies peaking at midday. Further, MGMT protein levels peaked at CT4, corresponding to the time of maximal TMZ efficacy in vitro. When we incorporated cell-intrinsic circadian rhythms in MGMT protein into a mathematical model for GBM chemotherapy, we found that dosing when daily MGMT levels peaked and began to decline produced maximum DNA damage. CONCLUSION: Our findings suggest that the likelihood of diagnosis of MGMT promoter methylation may vary with time of biopsy in GBM. Furthermore, theoretical modeling predicts that efforts to deliver TMZ after the daily peak of MGMT activity, with exact time being dose-dependent, may significantly enhance its therapeutic efficacy.

Humans

Putative glioblastoma origin-like cells in the subventricular zone: isolation and characterization.

Glioblastoma (GBM) remains lethal despite maximal therapy. The adult subventricular zone (SVZ), a neural stem-cell niche, has been implicated as a potential site of origin, yet the identity and functional properties of putative GBM origin-like cells (GBM-OCs) within the SVZ remain unclear. An SVZ-restricted somatic mutation mouse model (Cre-induced EGFRvIII expression with Trp53 and Pten disruption) was established and mouse SVZ-derived cells were prospectively isolated for functional and molecular profiling. Self-renewal, multipotency, invasive potential and tumour-initiating capacity were assessed relative to control SVZ cells and matched tumour-derived tumourspheres. Whole-genome and RNA sequencing defined genomic and transcriptional alterations during early progression. Mouse GBM-OCs exhibited self-renewal and multilineage differentiation and initiated tumours only after re-implantation into the SVZ (11/29, 38%), whereas direct striatal implantation failed (0/25, 0%), indicating context-dependent tumorigenic potential associated with the SVZ microenvironment. In contrast, tumour-derived tumourspheres retained tumorigenic capacity upon implantation into both the SVZ and the striatum. During progression from mouse GBM-OCs to tumours, whole-chromosome and arm-level aneuploidies accumulated. In patients with GBM, multi-region single-nucleus RNA sequencing of tumour-free SVZ, matched tumours and tumour-free cortex identified rare neural stem cell-like, astrocyte-like and oligodendrocyte precursor-like SVZ populations transcriptionally aligned with GBM programmes. These cells showed single-nucleus RNA-inferred chromosome 7 gain and/or chromosome 10 loss signals, with concordant low-frequency copy-number alterations in the SVZ detected by exome sequencing and enriched in matched tumours. Together, these findings support the presence of SVZ-resident stem or progenitor-like populations with early GBM-associated features, consistent with putative GBM-OCs, and highlight the SVZ niche as a potential target for early detection and niche-informed therapeutic strategies.

Animals

GBMdeconvoluteR accurately infers proportions of neoplastic and immune cell populations from bulk glioblastoma transcriptomics data.

BACKGROUND: Characterizing and quantifying cell types within glioblastoma (GBM) tumors at scale will facilitate a better understanding of the association between the cellular landscape and tumor phenotypes or clinical correlates. We aimed to develop a tool that deconvolutes immune and neoplastic cells within the GBM tumor microenvironment from bulk RNA sequencing data. METHODS: We developed an IDH wild-type (IDHwt) GBM-specific single immune cell reference consisting of B cells, T-cells, NK-cells, microglia, tumor associated macrophages, monocytes, mast and DC cells. We used this alongside an existing neoplastic single cell-type reference for astrocyte-like, oligodendrocyte- and neuronal progenitor-like and mesenchymal GBM cancer cells to create both marker and gene signature matrix-based deconvolution tools. We applied single-cell resolution imaging mass cytometry (IMC) to ten IDHwt GBM samples, five paired primary and recurrent tumors, to determine which deconvolution approach performed best. RESULTS: Marker-based deconvolution using GBM-tissue specific markers was most accurate for both immune cells and cancer cells, so we packaged this approach as GBMdeconvoluteR. We applied GBMdeconvoluteR to bulk GBM RNAseq data from The Cancer Genome Atlas and recapitulated recent findings from multi-omics single cell studies with regards associations between mesenchymal GBM cancer cells and both lymphoid and myeloid cells. Furthermore, we expanded upon this to show that these associations are stronger in patients with worse prognosis. CONCLUSIONS: GBMdeconvoluteR accurately quantifies immune and neoplastic cell proportions in IDHwt GBM bulk RNA sequencing data and is accessible here: https://gbmdeconvoluter.leeds.ac.uk.

Humans

First-in-Class Small Molecule Inhibitor of Oncogene AVIL in Glioblastoma.

Glioblastoma multiforme (GBM) is the most prevalent and aggressive malignant primary brain tumor, marked by rapid growth, extensive invasiveness, and a median survival of only ∼15 months despite current multimodal therapy. To identify new therapeutic vulnerabilities, we investigated the actin-regulatory protein AVIL, previously implicated through a MARS-AVIL gene fusion in rhabdomyosarcoma. Comprehensive genomic and transcriptomic analyses across REMBRANDT, TCGA, and CGGA datasets revealed recurrent AVIL amplification and consistently elevated AVIL expression in GBM compared with normal brain tissue. AVIL was overexpressed across all GBM molecular subtypes and glioma stem cell (GSC) states but was nearly undetectable in normal astrocytes, neural stem cells, and brain tissues. Functional studies demonstrated that AVIL is both necessary and sufficient for glioma genesis: AVIL silencing eradicated GBM cells in vitro and suppressed xenograft growth in vivo, while AVIL overexpression enhanced proliferation, migration, and transformation. Mechanistically, AVIL drives tumor progression through actin cytoskeleton remodeling and activation of the FOXM1-LIN28B oncogenic pathway. Using a small molecule microarray screen, we identified a selective AVIL-binding compound (compound A) that potently inhibited GBM cell growth with minimal toxicity to normal astrocytes. Gene expression changes induced by compound A mirrored those following AVIL knockdown, indicating on-target activity. Compound A demonstrated robust antitumor efficacy in multiple preclinical GBM models, including orthotopic xenografts, GSC-derived tumors, patient-derived xenografts, and temozolomide-resistant GBM with favorable pharmacokinetics and blood-brain barrier penetration. The minimal AVIL expression in normal tissues and lack of phenotype in AVIL-deficient mice underscore its potential as a low-toxicity therapeutic target. Together, these findings establish AVIL as a critical oncogenic driver in GBM and introduce a first-in-class AVIL inhibitor with strong translational promise for precision neuro-oncology.

Glioblastoma