TMIC-121. p52 promotes proliferation and immune evasion in glioma through distinct cell-intrinsic and -extrinsic mechanisms

Abstract BACKGROUND Glioblastoma (GBM) is the most common primary malignant intracranial neoplasm. p52, a central component of the non-canonical nuclear factor-κB pathway, regulates numerous targets involved in promoting inflammation and cancer. The role of p52 in GBM remains understudied but has the potential to elucidate novel therapies. METHODS We examined p52 mRNA and protein in multiple GBM datasets. Fresh patient-derived GBM cells were isolated and NF-κB profiled. Stemness and cell proliferation assays were performed. CRISPR-Cas9-and viral technology were utilized to modulate p52 expression in GBM cells. Unbiased RNA-sequencing was used to elucidate the p52-dependent expression profile. Intracranial allografts of p52 wild-type or knockout cells in immunocompetent and athymic nude mice were examined to evaluate tumor growth and animal survival. The immune landscape regulated by p52 was examined using flow cytometry. Lymphocyte-depleting antibodies were administered in immunocompetent nude mice to understand the role of T-cells in modulating the p52-dependent response. Anti-PD1 therapy was administered to mice with p52-wild type and knockout tumors to evaluate the role of combination immunotherapy and p52 inhibition in GBM. RESULTS Elevated p52 correlated with worse survival in GBM (P=0.04). p52 overexpression enhanced GBM cell stemness and proliferation, while loss of p52 induced G2/M cell cycle arrest. Overexpression of p52 led to pan immune checkpoint factor upregulation (P < 0.0001). In intracranially implanted tumors, loss of p52 in GBM cells resulted in increased animal survival. This was abrogated by CD4+/CD8+-lymphocyte-depletion and in athymic nude mice. Flow cytometric analysis revealed higher T-reg/CD8+ ratios in p52 wild-type tumors compared to p52-knockout tumors. Finally, loss of p52 when combined with anti-PD1 antibody resulted in significantly increased survival using highly resistant SB28 GBM model (P =0.01). CONCLUSION p52 promotes GBM cell growth cell-intrinsically by promoting cell cycle progression and promotes overall GBM pathobiology in a cell-extrinsic manner by inducing tumor immune evasion via T-cell response modulation. These findings highlight a role for p52 inhibition as a novel adjunct for improving GBM treatment.