Yuheng Geng

Introduction: Glioblastoma multiforme (GBM) pathobiology is characterized by its significant induction of immunosuppression within the tumor microenvironment, predominantly mediated by immunosuppressive tumor-associated myeloid cells (TAMCs). Myeloid cells play a pivotal role in shaping the GBM microenvironment and influencing immune responses, with direct interactions with effector immune cells critically impacting these processes. Methods: Our study investigates the role of the CXCR6/CXCL16 axis in T-cell myeloid interactions within GBM tissues. We examined the surface expression of CXCL16, revealing its limitation to TAMCs, while microglia release CXCL16 as a cytokine. The study explores how these distinct expression patterns affect T-cell engagement, focusing on the consequences for T-cell function within the tumor environment. Additionally, we assessed the significance of CXCR6 expression in T-cell activation and the initial migration to tumor tissues. Results: Our data demonstrates that CXCL16 surface expression on TAMCs results in predominant T-cell engagement with these cells, leading to impaired T-cell function within the tumor environment. Conversely, our findings highlight the essential role of CXCR6 expression in facilitating T-cell activation and initial migration to tumor tissues. The CXCL16-CXCR6 axis exhibits dualistic characteristics, facilitating the early stages of the T-cell immune response and promoting T-cell infiltration into tumors. However, once inside the tumor, this axis contributes to immunosuppression. Discussion: The dual nature of the CXCL16-CXCR6 axis underscores its potential as a therapeutic target in GBM. However, our results emphasize the importance of carefully considering the timing and context of intervention. While targeting this axis holds promise in combating GBM, the complex interplay between TAMCs, microglia, and T cells suggests that intervention strategies need to be tailored to optimize the balance between promoting antitumor immunity and preventing immunosuppression within the dynamic tumor microenvironment.

Glioblastoma is a Grade 4 primary brain tumor defined by therapy resistance, diffuse infiltration, and near-uniform lethality. The underlying mechanisms are unknown, and no treatment has been curative. Using a recently developed creatine kinase inhibitor (CKi), we explored the role of this inhibitor on GBM biology in vitro. While CKi minimally impacted GBM cell proliferation and viability, it significantly affected migration. In established GBM cell lines and patient-derived xenografts, CKi ablated both the migration and invasion of GBM cells. CKi also hindered radiation-induced migration. RNA-seq revealed a decrease in invasion-related genes, with an unexpected increase in glutathione metabolism and ferroptosis protection genes post-CKi treatment. The effects of CKi could be reversed by the addition of cell-permeable glutathione. Carbon-13 metabolite tracing indicated heightened glutathione biosynthesis post-CKi treatment. Combinatorial CKi blockade and glutathione inhibition or ferroptosis activation abrogated cell survival. Our data demonstrated that CKi perturbs promigratory and anti-ferroptotic roles in GBM, identifying the creatine kinase axis as a druggable target for GBM treatment.

Creatine, a naturally occurring compound in mammals, is crucial in energy metabolism, particularly within muscle and brain tissues. While creatine metabolism in cancer has been studied for several decades, emerging studies are beginning to clarify the sometimes-contradictory role creatine has in either the promotion or inhibition of cancer. On one hand, creatine can directly enhance anti-tumor CD8+ T-cell activity and induce tumor apoptosis, contributing to antitumor immunity. Conversely, other studies have shown that creatine can facilitate cancer cell growth and migration by providing an energy source and activating several signaling pathways. This review will examine what is known about creatine in cancer biology, with a focus on understanding its roles across different cellular compartments. Lastly, we discuss the emerging roles of creatine metabolism, providing exciting new insights into this often-overlooked pathway. This review highlights the complex role of creatine in cancer development and treatment, offering insights into its potential as both a therapeutic target and a risk factor in oncogenesis.

Abstract BACKGROUND Diffuse midline gliomas (DMG/DIPG) remain a devastating class of tumors with limited treatment options. Cancer vaccines educate the immune system to tumor neoantigens to facilitate immune-mediated tumor destruction. DMGs have high-frequency, co-occurring neoantigens and are therefore a relevant target for activation of anti-tumor immunity via vaccine. To this end, we have initiated a clinical trial (NCT04943848) to determine if a neoantigen peptide-based vaccine with recombinant human heat-shock constitutive protein 70 and QS-21 adjuvant can promote anti-tumor immunity against DMG/DIPG. NCT04943848 is ongoing and now enrolling subsequent arms with rHSC-DIPGVax plus checkpoint blockade. METHODS Whole blood was collected before the first vaccine cycle (C1D1). Vaccine doses were administered every 2 weeks and blood was collected prior to the third or fifth vaccine cycle (C3D1 & C5D1). Peripheral blood mononuclear cells (PBMCs) were isolated and stored at -160°C. PBMCs from each patient, pre- and post-vaccine, were stained with human T-cell, myeloid, and B-cell antibody panels before spectral flow cytometry, single-cell RNA sequencing, and genomic DNA isolation for T- and B-cell receptor (TCR/BCR) sequencing. Spectral flow cytometry data was analyzed via FlowJo v10. TCR/BCR sequencing was processed via MiXCR and Immunarch. RESULTS Following vaccination, there were higher percentages of two mature CD20+CD19+IgM+ B cell populations, including a 4-1BBL+CD86+ population previously shown to induce robust CD8+ T-cell activation in adults with glioblastoma. Interestingly, given the recent discovery of TIM3’s importance in DIPG, we also identified TIM3-expressing CD4+ and CD8+ T cell populations. Finally, TCR/BCR sequencing demonstrated increased receptor repertoire diversity after vaccination, which is indicative of the vaccine shaping adaptive immunity. CONCLUSIONS Peripheral immune populations and TCR/BCR sequences change during vaccination with rHSC-DIPGVax. Ongoing analyses will determine the specificity of the patient immune response to vaccine antigens and correlate changes in immune populations to clinical course.