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Repeated peripheral infusions of anti-EGFRvIII CAR T cells in combination with pembrolizumab remodel the tumor microenvironment in de novo glioblastoma

ABSTRACT: Treatment efficacy with chimeric antigen receptor (CAR) T cell therapy in glioblastoma (GBM) is undermined by an immunosuppressive tumor microenvironment (TME). We previously showed that CAR T cell therapy targeting epidermal growth factor receptor variant III (EGFRvIII) produces anti-tumor activity against recurrent GBM and causes upregulation of programmed death-ligand 1 (PD-L1) in the TME. Here, we conducted a phase I trial to study the safety and tolerability of CART-EGFRvIII cells administered concomitantly with the PD-1 inhibitor pembrolizumab in patients with newly diagnosed, EGFRvIII+ GBM (n=7). Treatment was well tolerated in this small cohort without incidence of dose-limiting toxicity. However, no signal of efficacy was detected with a median progression-free survival of 5.2 months (90% CI, 2.9 – 6.0 months) and overall survival of 11.8 months (90 % CI, 9.2 – 14.2 months). We aimed to elucidate reasons for limited efficacy through correlative analyses. Using BBZ qPCR, we found circulating CAR T cells in 5 out of 7 patients at the time of repeat resection, but only in 1 patient in the tumor. However, shared T-cell receptors (TCRs) were found between the infusion product and the relapsed tumors, which could indicate an infiltration but lack of persistence of the CAR T cells. We further compared the tumor microenvironment of the tumors harvested before and after CAR+aPD1 administration using single cell RNA sequencing and observed comparable proportions of the major immune cell subsets. However, the myeloid and T cells infiltrating the tumors significantly evolved, with more exhausted, regulatory, and IFN-stimulated T cells at the relapse. At that time, the amount of IFN-stimulated T cells positively correlated with time from relapse to death. Together, these findings suggest that the combination of CAR T cells and PD-1 inhibition in GBM is safe and biologically active but, given the lack of efficacy, also indicate a need to consider alternative immunotherapeutic strategies. ClinicalTrials.gov registration: NCT03726515.

ORGANISM(S): Homo sapiens

PROVIDER: GSE242790 | GEO | 2023/09/12

REPOSITORIES: GEO

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Project description:PD-L1 Inhibitor Regulates the miR-33a-5p/PTEN Signaling Pathway and Can Be Targeted to Sensitize Glioblastomas to Radiation. Glioblastoma (GBM) is the most common and lethal brain tumor in adults. Ionizing radiation (IR) is a standard treatment for GBM patients and results in DNA damage. However, the clinical efficacy of IR is limited due to therapeutic resistance. The programmed death ligand 1 (PD-L1) blockade has a shown the potential to increase the efficacy of radiotherapy by inhibiting DNA damage and repair responses. The miR-33a-5p is an essential microRNA that promotes GBM growth and self-renewal. In this study, we investigated whether a PD-L1 inhibitor (a small molecule inhibitor) exerted radio-sensitive effects to impart an anti-tumor function in GBM cells by modulating miR-33a-5p. U87 MG cells and U251 cells were pretreated with PD-L1 inhibitor. The PD-L1 inhibitor-induced radio-sensitivity in these cells was assessed by assaying cellular apoptosis, clonogenic survival assays, and migration. TargetScan and luciferase assay showed that miR-33a-5p targeted the phosphatase and tensin homolog (PTEN) 3' untranslated region. The expression level of PTEN was measured by western blotting, and was also silenced using small interfering RNAs. The levels of DNA damage following radiation was measured by the presence of γ-H2AX foci, cell cycle, and the mRNA of the DNA damage-related genes, BRCA1, NBS1, RAD50, and MRE11. Our results demonstrated that the PD-L1 inhibitor significantly decreased the expression of the target gene, miR-33a-5p. In addition, pretreatment of U87 MG and U251 cells with the PD-L1 inhibitor increased radio-sensitivity, as indicated by increased apoptosis, while decreased survival and migration of GBM cells. Mir-33a-5p overexpression or silencing PTEN in U87 MG and U251 cells significantly attenuated PD-L1 radiosensitive effect. Additionally, PD-L1 inhibitor treatment suppressed the expression of the DNA damage response-related genes, BRCA1, NBS1, RAD50, and MRE11. Our results demonstrated a novel role for the PD-L1 inhibitor in inducing radio- sensitivity in GBM cells, where inhibiting miR-33a-5p, leading to PTEN activated, and inducing DNA damage was crucial for antitumor immunotherapies to treat GBM.

Project description:Glioblastoma multiforme (GBM) is a highly aggressive and heterogeneous form of primary brain tumors, driven by a complex repertoire of oncogenic alterations, including the constitutively active epidermal growth factor receptor (EGFRvIII). EGFRvIII impacts both cell-intrinsic and non-cell autonomous aspects of GBM progression, including cell invasion, angiogenesis and modulation of the tumor microenvoiront, this is, at least in part, attributable to the release and intercellular trafficking of extracellular vesicles (EVs), heterogeneous membrane structures containing multiple bioactive macromolecules. Here we analyzed the impact of EGFRvIII on the profile of glioma EVs using a series of isogenic tumor cell lines, in which this oncogene exhibits a strong transforming activity. Thus, we observed that EGFRvIII expression alters several properties of glioma EVs, including their output and global protein composition. Using mass spectrometry, quantitative proteomic analysis and Gene Ontology terms filters, we observed that EVs released by EGFRVIII-transformed cells were enriched for extracellular exosome and focal adhesion related proteins. Among them, we validated the association of pro-invasive proteins (CD44, BSG, CD151) with EVs of EGFRvIII expressing cells, and down-regulation of exosomal markers (CD81 and CD82) in EVs of their indolent counterparts. Nano-flow cytometry revealed that the EV output from individual glioma cell lines was highly heterogeneous, such that only a fraction of EVs contained specific proteins such as EGFR, CD9, or others. Notably, cells expressing EGFRvIII released ample EVs double positive for CD44/BSG, and these proteins also co-localized in cellular filopodia. We also detected the expression of homophilic adhesion molecules and increased homologous EV uptake by EGFRvIII-positive glioma cells. These results suggest that oncogenic EGFRvIII reprograms the proteome of GBM-related EVs, a notion with considerable implications for their biological activity and properties relevant for development of EV-based cancer biomarkers.

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Repeated peripheral infusions of anti-EGFRvIII CAR T cells in combination with pembrolizumab remodel the tumor microenvironment in de novo glioblastoma

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