Benzo(a)pyrene promotes malignant progression of human lung cancer LTEP-a-2 cells through the NLRP3 pyroptosis signaling pathway: Validation based on bioinformatics and cellular experiments

Benzo(a)pyrene (BaP), as the most common polycyclic aromatic hydrocarbon pollutant, exhibits potent carcinogenic, teratogenic, and inflammatory toxic effects. Previous studies have demonstrated that BaP promotes invasion and migration capabilities of human bronchial epithelial cells following malignant transformation by suppressing ferroptosis; however, whether BaP can regulate tumor cell pyroptosis remains unclear. This study aims to elucidate the mechanism by which BaP promotes lung cancer invasion and migration through suppressing pyroptosis in human lung cancer cell line LTEP-a-2.

Potential target genes of BaP were retrieved from the Comparative Toxicogenomics Database (CTD), and lung cancer-related differentially expressed genes (DEGs) were screened from the Gene Expression Omnibus (GEO) database. Subsequently, an intersection analysis of these 2 gene sets was performed to obtain key candidate genes. Protein-Protein Interaction (PPI) network analysis on these candidate genes was conducted using the STRING database, and topological attribute analysis was performed for topological properties with Cytoscape software to screen key hub target genes based on high node degree values. Survival analysis of these PPI-derived hub genes was performed using the Kaplan-Meier Plotter database. Molecular docking simulations between BaP and each target protein were conducted with AutoDock Vina to predict binding conformations and calculate binding free energies. Visualization and analysis of the docking results were carried out using PyMOL software, and detailed ligand-receptor interactions were visualized and analyzed using 2D interaction diagrams generated by LigPlot+. LTEP-a-2 cells were exposed to gradient concentrations of BaP (0, 0.1, 1, and 10 μmol/L) for 48 h. Subsequently, cell viability was evaluated with CCK-8 assay, invasive and migratory capabilities were assessed with Transwell assay, cytotoxicity was determined by lactate dehydrogenase (LDH) release assay, and apoptosis was detected via Annexin V-FITC/PI flow cytometry. The concentrations of IL-1β and IL-18 in the supernatant were determined by enzyme-linked immunosorbent assay (ELISA). RT-qPCR and Western blotting were performed to measure the expression of key pyroptosis-related molecules (NLRP3, ASC, caspase-1, GSDMD, IL-1β, and IL-18) at mRNA and protein levels. Cell viability and invasive/migratory capabilities were assessed after LTEP-a-2 cells treated with BaP combined with pyroptosis agonists, as well as pyroptosis inhibitors combined with pyroptosis agonists. Concurrently, alterations in pyroptosis-related indicators, including IL-1β/IL-18 release and expression of the aforementioned key molecules, were examined.

In vitro experiments demonstrated that compared to the control group, exposure to 1 or 10 μmol/L BaP significantly promoted the proliferation, invasion, and migration of LTEP-a-2 cells (P<0.01), but did not induced obvious changes in apoptosis. Bioinformatics analysis revealed significant enrichment of BaP-related genes in the pyroptosis pathway. Treatment with different doses of BaP significantly inhibited pyroptosis, as evidenced by reduced LDH release (P<0.05), downregulated secretion levels of the inflammatory cytokines IL-1β and IL-18, and notable decreases in both mRNA and protein expression levels of key molecules in the pyroptosis pathway (NLRP3, ASC, caspase-1, GSDMD, IL-1β, and IL-18) (P<0.05). Conversely, pyroptosis agonist (compared to the control group) induced pronounced pyroptotic phenotypes and suppressed cell proliferation and invasive and migratory capacities (P<0.05). In the BaP or pyroptosis inhibitor combined with pyroptosis agonist treatment groups, the inhibitory effects of the agonists on tumor cell proliferation and invasion/migration were significantly reversed (P<0.01). Bioinformatics prediction and molecular docking analysis indicated that NLRP3 and PTGS2 may serve as potential molecular targets for BaP-mediated regulation of pyroptosis in lung cancer cells.

BaP promotes the invasion and migration of LTEP-a-2 cells by inhibiting the NLRP3-caspase-1-GSDMD pyroptosis signaling pathway.