BIOM-43. TARGETING GRP78 WITH PAT-SM6 DISRUPTS GLIOBLASTOMA METABOLISM AND TUMOR GROWTH

Abstract Glioblastoma (GBM) is the most lethal primary brain tumor characterized by endoplasmic reticulum (ER) stress and metabolic plasticity. GRP78, an ER chaperone protein, supports tumor cell survival. We evaluated the therapeutic potential of the GRP78-targeting antibody PAT-SM6 using integrated omics and functional assays. Dose–response experiments were performed on GBM cell lines (A172, AHN) treated with PAT-SM6 (0–50 µg/mL). Cell viability (MTT), apoptosis (TUNEL, caspase-12), and migration (transwell, circulating tumor cell markers) were assessed. GRP78 expression was measured in patient-derived GBM tissues and cell lines by immunoblotting, qRT-PCR, and immunohistochemistry. Proteomics was performed by TMT-based LC-MS/MS and metabolomics by GC-MS. In vivo efficacy was tested in GL261 orthotopic mouse models, including GRP78-knockout. PAT-SM6 induced dose-dependent cytotoxicity, with maximal suppression at 12.5 µg/mL in A172 cells (p=0.004), sparing normal astrocytes (p=0.89). GRP78 was elevated 2.5–3.7-fold in patient GBM tissues versus normal brain (p=0.01). Apoptosis increased, demonstrated by TUNEL positivity (p=0.006) and caspase-12 activation (p=0.003). Migration assays showed reduced invasiveness and decreased circulating tumor markers (p=0.02). Proteomics revealed downregulation of glycolytic enzymes PKM2 (–2.3-fold, p=0.02), ENO2 (–2.1-fold, p=0.03), RNA-binding proteins HNRNPF (–4.3-fold) and UBQLN2 (–12.8-fold), and vimentin (–9.5-fold), with suppression of ER stress markers CALR, EIF2, and PDI. GC-MS showed decreased hexokinase, GAPDH, and enolase activity (p<0.05) and a 4.2-fold increase in pyruvate (p=0.01), indicating glycolytic collapse. UPR markers ATF6 and CHOP were significantly induced (p<0.05). In vivo, PAT-SM6 reduced tumor burden (p<0.01), with enhanced effect in GRP78-KO mice (p=0.004). PAT-SM6 selectively targets GRP78 to induce apoptosis, disrupt glycolysis, and inhibit migration in GBM, leading to decreased tumor growth, especially when GRP78 is genetically ablated. Combination studies with temozolomide and GRP78 biomarker validation are underway to improve therapeutic strategies against GBM.