Abstract 4909: Microbial stimuli differentially regulate astrocyte and glioblastoma cell phenotypes

Abstract Glioblastoma multiforme (GBM), an astrocytoma, is the most prevalent and aggressive primary brain tumor. These tumors present with an intricate molecular profile and resistance to treatment, thus resulting in poor prognosis. Astrocytes, the most abundant cells in the brain, maintain the blood-brain barrier (BBB) and support metabolic homeostasis. Studies have shown that, when exposed to inflammation, they can acquire a reactive phenotype, possibly contributing brain carcinogenesis. However, the mechanisms behind their role in tumor development remain unclear, highlighting the need to further understand the phenotype of astrocytes in GBM. Lipopolysaccharides (LPS) from periodontal disease-causing pathogen Porphyromonas gingivalis (Pg) are known endotoxins capable of crossing the BBB, inducing strong inflammatory responses. Thus, understanding the role of common microbial products in the brain microenvironment, and their influence on GBM pathogenesis is key. To assess this response, astrocytes and U87-GBM cells were cultured and exposed directly to Pg-LPS, Staphylococcus aureus lipoteichoic acids (Sa-LTA) and Escherichia coli lipopolysaccharides (Ec-LPS). Indirect treatments were also performed using astrocyte-conditioned media (ACM) primed with Pg-LPS, Sa-LTA and Ec-LPC. After 24- and 48-hour exposures, cytokine and protein expression were measured by ELLA assays and immunofluorescence (IF) respectively. Viability was assessed via MTT Assay. At 24 hours, exposure to Pg-LPS significantly increased astrocyte metabolic activity when compared to other treatments (p = 0.042), though this effect was not observed at 48 hours. IF staining of proliferation marker Ki67 in astrocytes revealed a significant increase when treated with Pg-LPS (p = 0.033) for 24H. In contrast, Pg-LPS-primed ACM for 48H, decreased proliferation in GBM cells compared to untreated (p = 0.007), directly treated U87-GBM cells with Pg-LPS (p = 0.003), and not-primed astrocyte-conditioned media (p = 0.024). GBM cells expressed consistently higher levels of Ki67 than all astrocyte treatments and viability remained unchanged across treatments. Moreover, Pg-LPS-primed ACM presented detectable levels of IL-10, IFN-a2, IL-4 and TGF-beta. Our results suggest that Pg-LPS promotes a shift toward an anti-inflammatory phenotype and may reduce proliferation in GBM cells. Further studies are needed to elucidate how Pg-LPS-conditioned astrocytes modulate GBM progression. Citation Format: Ariana N. De Jesus-Carrasquillo, Claudia M. Ramos-Lugo, Aliaha Serpa-Figueroa, Alondra Soto-Nieves, Alexander Y. Morlá-Sevilla, Yaraliz Corchado-Vargas, Joseph Torres-Cruz, Yisel M. Cantres-Rosario. Microbial stimuli differentially regulate astrocyte and glioblastoma cell phenotypes [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 4909.