Human Plasma-Like Medium Activates Immune Elements in Glioma

Abstract

INTRODUCTION: Glioma Surgically eXplanted Organoids (SXOs) are ex vivo three-dimensional models demonstrated to recapitulate the parental tumor microenvironment (TME). Human plasma-like medium (HPLM), a culture medium that mirrors physiologic nutrient conditions, has been found in other cancer subtypes to induce transcriptional differences in T-lymphocyte activation. We hypothesized that SXO culture in HPLM would maintain immune cell populations and induce physiologically relevant immune-modulatory pathways. METHODS: SXOs were established and cultured in conventional Glioma Organoid Complete medium (GOC) and transitioned to HPLM for 24 or 120 hours. Formalin-fixed paraffin-embedded samples were stained for tumor cells (GFAP), immune cells (CD45), and nucleic acid (SYTO-13) and analyzed using the Nanostring GeoMx™ Digital Spatial Profiler for spatial transcriptomics. Gene expression clustering profiles were conducted using GSEA and CIBERSORT. The gene expression differences of SXOs cultured in HPLM for 24 and 120 hours compared to those in GOC were analyzed by unpaired t-tests. RESULTS: Glioma SXOs retain diverse cell populations, with 20-30% of cells belonging to the TME. CD4+ T-cells were the most common (9.7 ± 1.0), followed by CD8+ T-cells (4.4 ± 0.6) and macrophages (3.1 ± 1.2). Following the transition to HPLM for 24 or 120 hours, there were no significant differences in tumor, immune, and stromal cell fractions. HPLM culture upregulated the immune response in SXOs, encompassing enhanced cytokine secretion, as well as improved adaptive and innate immune pathways. We particularly highlighted CD4+ T-cell activation (CD69+), Treg, and TGF-β signaling pathways as significantly increased. CONCLUSIONS: Here, we present that the culture of SXOs in physiologically similar media retains the heterogeneous TME and activates innate and adaptive immune signaling pathways. Culture in HPLM enables investigation of the glioma immune microenvironment, expanding the biological relevance of experimental results from in vitro SXO models.