Homozygous deletion of methylthioadenosine phosphorylase (MTAP) is one of the most frequent genetic alterations in glioblastoma (GBM), but its pathologic consequences remain unclear. In this study, we report that loss of MTAP results in profound epigenetic reprogramming characterized by hypomethylation of PROM1/CD133-associated stem cell regulatory pathways. MTAP deficiency promotes glioma stem-like cell (GSC) formation with increased expression of PROM1/ CD133 and enhanced tumorigenicity of GBM cells and is associated with poor prognosis in patients with GBM. As a combined consequence of purine production deficiency in MTAP-null GBM and the critical dependence of GSCs on purines, the enriched subset of CD133 þ cells in MTAP-null GBM can be effectively depleted by inhibition of de novo purine synthesis. These findings suggest that MTAP loss promotes the pathogenesis of GBM by shaping the epigenetic landscape and stemness of GBM cells while simultaneously providing a unique opportunity for GBM therapeutics. Significance: This study links the frequently mutated metabolic enzyme MTAP to dysregulated epigenetics and cancer cell stemness and establishes MTAP status as a factor for consideration in characterizing GBM and developing therapeutic strategies.
BackgroundSym004 is a mixture of two monoclonal antibodies (mAbs), futuximab and modotuximab, targeting non-overlapping epitopes on the epidermal growth factor receptor (EGFR). Previous studies have shown that Sym004 is more efficient at inducing internalization and degradation of EGFR than individual components, which translates into superior cancer cell inhibition. We investigated whether Sym004 induces removal of EGFRvIII and if this removal translates into tumor growth inhibition in hard-to-treat glioblastomas (GBMs) harboring the mutated, constitutively active EGFR variant III (EGFRvIII).MethodsTo address this question, we tested the effect of Sym004 versus cetuximab in eight patient-derived GBM xenograft models expressing either wild-type EGFR (EGFRwt) and/or mutant EGFRvIII. All models were tested as both subcutaneous and orthotopic intracranial xenograft models.ResultsIn vitro studies demonstrated that Sym004 internalized and removed EGFRvIII more efficiently than mAbs, futuximab, modotuximab, and cetuximab. Removal of EGFRvIII by Sym004 translated into significant in vivo anti-tumor activity in all six EGFRvIII xenograft models. Furthermore, the anti-tumor activity of Sym004 in vivo was superior to that of its individual components, futuximab and modotuximab, suggesting a clear synergistic effect of the mAbs in the mixture.ConclusionThese results demonstrate the broad activity of Sym004 in patient-derived EGFRvIII-expressing GBM xenograft models and provide a clear rationale for clinical evaluation of Sym004 in EGFRvIII-positive adult GBM patients.Electronic supplementary materialThe online version of this article (10.1007/s11060-018-2832-6) contains supplementary material, which is available to authorized users.
Background: The complex and dynamic nature of the tumor-immune microenvironment presents challenges for identification of robust and predictive biomarkers in immuno-oncology (IO). Multiplex immunohistochemistry (mIHC) facilitates the ability to detect, phenotype, and quantify spatial relationships of cells within the tumor microenvironment (TME). Gene expression profiling allows for sensitive and high-throughput analysis of genes and signatures associated with the tumor, the immune response, and the TME, allowing examination of tumor-immune cell interactions. We used these approaches to generate multiple data sets from a cohort of HNSCC tumors and evaluated the correlation of the various analyte detection methods. These complementary technologies provide useful tools in the IO biomarker toolkit. Methods: Formalin-fixed paraffin-embedded (FFPE) specimens from HNSCC patients were cut into 5µm sections for all technologies. Multiplex fluorescent IHC was performed for TME markers CD3, CD8, PD-L1, PD1, CD68, Granzyme B, Ki67, and panCK/SOX10. Visualization and data analysis were performed with an Akoya Vectra Polaris and Akoya inForm and HALO software (Indica Labs). Data analysis included cell identification, phenotyping, spatial relationships, and quantitative digital pathology. Gene expression for 770 genes was performed utilizing the NanoString PanCancer IO 360 Gene Expression Panel. Transcripts were quantitated using a NanoString nCounter and target gene counts were normalized to internal housekeeping genes. Results: Analysis of the multiplex fluorescent IHC indicated a range of expression for the assayed TME biomarkers for the different tumor samples. Quantitative analysis of mIHC phenotype counts and normalized RNA counts for the targets contained in the antibody panel revealed a significant correlation between the analytic methods. Comparison of mIHC phenotype counts with a previously validated IO gene signature containing a broader set of IO-relevant genes, the Tumor Information Signature, (Ayers, et al., J Clin Invest. 2017; 127:2930) also showed a correlation. Conclusions: The technologies described above enable the investigation of the TME for use in biomarker discovery, drug discovery, and IO pathway interrogation. These technologies can be used in parallel to uncover roles in the biomarker discovery pathway for genes of interest. The combination of mIHC and gene expression panels can be used to screen a broad range of targets, that then can be further investigated using the spatial analysis capabilities of mIHC to gain greater insight into the immune infiltrate density at any singular area of the TME. Citation Format: Carlee Hemphill, Timothy Maynor, John Bauman, Caitlin Schroyer, Jeffery Shuster, Thomas Turi, Steven M. Anderson. Multiplex immunohistochemistry, spatial analysis, and gene expression profiling of the tumor-immune microenvironment in HNSCC tumors [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2637.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.