2025-04-12 | | Total: 7
Glioblastoma (GBM) is a common and highly lethal type of primary brain tumor in adults. Therapeutic failure is partly attributed to a fraction of Glioblastoma Stem Cells (GSCs) that show high levels of heterogeneity and plasticity. GSCs exist in a transcriptional gradient between two states: Developmental (Dev) and Injury Response (IR) in which IR-GSCs exhibit more invasive behaviors. While previous studies have identified fitness genes in GSCs, the genes required to establish and maintain the Dev and IR states remain poorly defined. To identify the regulators of the IR GSC state, we performed a phenotypic genome-wide CRISPR-Cas9 knockout (KO) screen in patient-derived GSCs based on cell surface expression of the IR marker CD44. Notably, we found that perturbations of the histone acetyltransferase EP300 in IR GSCs led to decreased CD44 cell surface expression, significant downregulation of gene expression signatures associated with the IR state, and to decreased self-renewal and invasion. Furthermore, genetic targeting of Ep300 in a mouse GBM model delayed tumor initiation and/or progression. Collectively, our results establish EP300 as a regulator of the IR state in GSCs and provide a mechanistic basis for its therapeutic targeting in GBM.
Tumor-infiltrating lymphocyte (TIL) therapy, recently approved by the FDA for melanoma, is an emerging modality for cell-based immunotherapy. However, its application in immunologically 'cold' tumors such as glioblastoma remains limited due to sparse T cell infiltration, antigenic heterogeneity, and a suppressive tumor microenvironment. To identify genomic and spatial determinants of TIL expandability, we performed integrated, multimodal profiling of high-grade gliomas using spectral flow cytometry, TCR sequencing, single-cell RNA-seq, Xenium in situ transcriptomics, and CODEX spatial proteomics. Comparative analysis of TIL-generating (TIL⁺) versus non-generating (TIL⁻) tumors revealed that IL7R expression, structured perivascular immune clustering, and tumor-intrinsic metabolic programs such as ACSS3 were associated with successful TIL expansion. In contrast, TIL⁻ tumors were enriched for neuronal lineage signatures, immunosuppressive transcripts including TOX and FERMT1, and tumor-connected macrophages. This study defines spatial and molecular correlates of TIL manufacturing success and establishes a genomics-enabled selection platform for adoptive T cell therapy. The profiling approach is now being prospectively implemented in the GIANT clinical trial (NCT06816927), supporting its translational relevance and scalability across glioblastoma and other immune-excluded cancers.
Purine metabolism is a promising therapeutic target in cancer; however how cancer cells respond to purine shortage,particularly their adaptation and vulnerabilities, remains unclear. Using the recently developed purine shortage-inducing prodrug DRP-104 and genetic approaches, we investigated these responses in prostate, lung and glioma cancer models. We demonstrate that when de novo purine biosynthesis is compromised, cancer cells employ microtubules to assemble purinosomes, multi-protein complexes of de novo purine biosynthesis enzymes that enhance purine biosynthesis efficiency. While this process enables tumor cells to adapt to purine shortage stress, it also renders them more susceptible to the microtubule-stabilizing chemotherapeutic drug Docetaxel. Furthermore, we show that although cancer cells primarily rely on de novo purine biosynthesis, they also exploit Methylthioadenosine Phosphorylase (MTAP)-mediated purine salvage as a crucial alternative source of purine supply, especially under purine shortage stress. In support of this finding, combining DRP-104 with an MTAP inhibitor significantly enhances tumor suppression in prostate cancer (PCa) models in vivo. Finally, despite the resilience of the purine supply machinery, purine shortage-stressed tumor cells exhibit increased DNA damage and activation of the cGAS-STING pathway, which may contribute to impaired immunoevasion and provide a molecular basis of the previously observed DRP-104-induced anti-tumor immunity. Together, these findings reveal purinosome assembly and purine salvage as key mechanisms of cancer cell adaptation and resilience to purine shortage while identifying microtubules, MTAP, and immunoevasion deficits as therapeutic vulnerabilities.
The efficacy of T cell-activating therapies against glioma is limited by an immunosuppressive tumor microenvironment and tumor-induced T cell sequestration. We investigated whether peripherally infused non-antigen specific autologous lymphocytes (ALT) could accumulate in intracranial tumors. We observed that non-specific autologous CD8+ ALT cells can indeed accumulate in this context, despite endogenous T cell sequestration in bone marrow. Rates of intratumoral accumulation were significantly increased when expanding lymphocytes with IL-7 compared to IL-2. Pre-treatment with IL-7 ALT also enhanced the efficacy of multiple tumor-specific and non-tumor-specific T cell-dependent immunotherapies against orthotopic murine and human xenograft gliomas. Mechanistically, we detected increased VLA-4 on mouse and human CD8+ T cells following IL-7 expansion, with increased transcription of genes associated with migratory integrin expression (CD9). We also observed that IL-7 increases S1PR1 transcription in human CD8+ T cells, which we have shown to be protective against tumor-induced T cell sequestration. These observations demonstrate that expansion with IL-7 enhances the capacity of ALT to accumulate within intracranial tumors, and that pre-treatment with IL-7 ALT can boost the efficacy of subsequent T cell-activating therapies against glioma. Our findings will inform the development of future clinical trials where ALT pre-treatment can be combined with T cell-activating therapies.
The impact of the microenvironment on epigenetically plastic cancer cells underpins phenotypic heterogeneity, a major cause of metastatic dissemination and therapy resistance that together represent the primary cause of cancer-related death. Nutrient limitation is a key microenvironmental stress that can cause a phenotypic transition from proliferation to invasion via activation of the integrated stress response. However, whether and how the capacity to store and mobilize nutrients impacts phenotype-switching through metabolic buffering remains unknown. Here, using melanoma as a model, we reveal that the ability to accumulate and mobilize glycogen, that buffers glucose availability, plays a key role in phenotypic transitions in melanoma. While proliferative phenotype cells exhibit high levels of glycogen, invasion is marked by low glycogen levels. Significantly, an inability to store and metabolize glycogen leads to phenotype instability and a switch to invasion. Accordingly, glycogen levels inversely correlate with Clark levels in primary melanomas, with low expression of the glycogen phosphorylases PYGB/L and phosphoglucomutase 1 (PGM1) being associated with worse overall survival. The importance of metabolic buffering in suppressing phenotypic transitions likely extrapolates to other cancer types.
Reinvigoration of tumor-reactive T-cells using co-stimulatory bispecific antibodies (bsAbs) targeting CD28 or CD137 is emerging as a promising therapeutic strategy. Conditional, tumor-specific recruitment can offer a necessary layer of control and specificity. We developed pH-selective CD28xVISTA bsAbs to act specifically within the acidic tumor microenvironment (TME), aiming for enhanced T-cell-mediated cancer cell killing while minimizing systemic T-cell activation and Cytokine Release Syndrome (CRS) risk. CD28 agonism by CD28xVISTA bsAbs relies on pH-selective engagement of VISTA, a protein robustly expressed on myeloid cells highly prevalent in most solid tumors. This modality avoids engagement of tumor-associated antigens (TAAs) with the potential to provide highly tumor specific activity with minimal on-target/off-tumor side effects. We report the identification of a lead candidate with pH-dependent simultaneous engagement of both targets, and VISTA-dependent CD28 signaling in a reporter cell line. CD28xVISTA avidly bound VISTA-positive cells, and co-stimulation was shown in vitro by its ability to activate and expand T-cells and enhance T-cell mediated cancer cell killing in co-cultures of human PBMCs and cancer cells in the presence of a TAA-targeted anti-CD3 T-cell engager. Interestingly, our findings support both signaling in cis (between T-cell and cell displaying peptide-MHC complex) and in trans with stimulation occurring through CD28 clustering outside of the immune synapse. Our lead candidate displayed efficient tumor growth inhibition of human VISTA-expressing MC38 cells in a humanized CD28 syngeneic mouse model in combination with PD-1 blockade. Importantly, our CD28xVISTA bsAb showed no signs of superagonistic properties in several in vitro assays geared towards revealing induction of CRS. Our data supports clinical development in combination with anti-PD-1 or any TAA-targeted anti-CD3 T-cell engagers developed for solid tumors.
Glutamine serves as a major fuel source for tumor cell proliferation while simultaneously playing an essential role in maintaining gastrointestinal health and immune function. Controversy exists regarding glutamine supplementation for cancer patients undergoing chemotherapy and radiation, with concerns that it may stimulate cancer growth. The present study is the first to examine the effects of dietary glutamine supplementation (0.4g/kg/day) on the growth of malignant gliomas, which utilize large amounts of glutamine to satisfy metabolic demands. Brain bioluminescence and subcutaneous tumor volumes were used to assess the influence of glutamine supplementation on the growth of the syngeneic VM-M3 and CT-2A preclinical models of glioma. Glutamine supplementation had no significant effect on the orthotopic growth of the VM-M3 or the CT-2A gliomas when compared to non-supplemented controls. However, glutamine supplementation significantly increased tumor volume by 28% in the VM-M3 and by 166% in the CT-2A tumors when grown subcutaneously outside the central nervous system (CNS) relative to controls. Additionally, glutamine supplementation increased serum glutamine despite a localized decrease in intratumoral glutamine concentrations. Caution is warranted when considering glutamine supplementation in patients with glutamine-dependent malignancies. Further studies are needed to better understand the potential risks and benefits of glutamine supplementation in cancer therapy.