Unraveling the role of NLRP1-mediated inflammation in glioblastoma pathophysiology.

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Background: Glioblastoma (GBM) is the most aggressive type of brain cancer with a median survival of less than 14 months even after surgery, chemo, and radiotherapy. Innate and adaptive immune cells express members of the nucleotide-binding domain, leucine-rich repeat-containing receptors (NLRs), a family of pattern recognition receptors. NLRs are central to innate immunity, detect danger signals, and form a multi-protein cytosolic complex called the inflammasome that plays a critical role in regulating innate immunity and cancer development. NLRP1 is the first discovered inflammasome sensor that contains a pyrin domain, leucine-rich repeats (LRRs), and a caspase recruitment domain (CARD). The CARD domain recruits Caspase-1 that can cleave pro-inflammatory cytokines IL-1β and IL-18, which may regulate cell death. NLRP1 inflammasome activation positively correlates with breast cancer. The exact role of NLRP1 in glioblastoma remains undiscovered. This research aims to assess the role of NLRP1 in glioblastoma pathophysiology. Methods: RNA-seq data from TCGA-LGG (low-grade glioma) (n=523), TCGA-GBM (n=166), and GTEx normal brain tissues (n=1141) were taken from the UCSC Xena platform. Differential expression across tumor grades was analyzed using R packages (v4.4.1). Overall survival (OS) was assessed using Kaplan–Meier analysis with log-rank testing. Immune cell infiltration correlations were evaluated using TIMER 2.0 with the CIBERSORT algorithm. DNA methylation data from TCGA were analyzed to assess correlations between promoter-associated CpG β-values and NLRP1 expression. NLRP1 protein expression was evaluated using immunohistochemistry and immunocytochemistry on normal and GBM tissue and cell lines, respectively. Results: NLRP1 expression was significantly elevated in lower-grade glioma (LGG) relative to GBM and normal brain tissue. Low-grade glioma patients with high NLRP1 expression demonstrate significantly poorer overall survival (p=0.027). NLRP1-associated immune cell infiltration is higher in lower-grade glioma than in GBM. Promoter-proximal CpG sites showed moderate-to-strong negative correlations with expression. ICC shows NLRP1 is differentially expressed in astrocytes (SVG) and GBM (LN229) cell lines. NLRP1 is differentially expressed in the astrocytes and microglia of GBM and the non-tumor-associated brain tissues. Conclusions: NLRP1 integrates with the remodeling of the GBM microenvironment and is associated with adverse survival in LGG. These findings position NLRP1 as a potential prognostic biomarker and immunometabolic therapeutic target.