Smoking-Driven Inflammasome-Associated Inflammation in Colorectal Cancer: A Two-Phase Discovery and Validation Study of Serum Biomarkers

Abstract

Introduction: To identify and validate serum biomarkers of smoking-related inflammasome activation in CRC and quantify the mediating role of inflammatory markers in the smoking–CRC association. Materials and Methods: This two-phase retrospective study was conducted at the Oncology Teaching Hospital, Baghdad Medical City, Iraq, from April 2024 to April 2025. A total of 200 participants were enrolled and evenly divided into four groups (n 50 each): non-smoker controls, smoker controls, non-smoker colorectal cancer (CRC) patients, and smoker CRC patients. nine serum biomarkers were measured using ELISA assays, including interleukin-8 (IL-8), interleukin-37 (IL-37), C-reactive protein (CRP), adiponectin, forkhead box P3 (FoxP3), sestrin-1, galectin-1, P selectin, and carcinoembryonic antigen (CEA). Three composite indices (Provisional Smoking-Driven Inflammasome Score - pSIS, Provisional Smoking-Attributable Risk Index - pSMRI, and Provisional Pyroptosis Activity Score - pPAS) were calculated. Statistical analyses involved mediation analysis, LASSO regression, and random forest with Boruta feature selection. Results: Outcomes revealed that smokers with CRC exhibited a distinct pro-inflammatory signature, characterized by significantly elevated IL-8, CRP, and galectin-1, alongside reduced IL-37 and adiponectin. Mediation analysis showed that these three markers collectively mediated 73.8% (95% CI: 52.1%–89.3%) of the smoking–CRC relationship. The three composite indices (pSIS, pSMRI, and pPAS) showed progressively increasing median values from healthy controls to smoker CRC patients (p < 0.001). All three indices demonstrated excellent discriminatory ability, with area under the curve (AUC) values of 0.92 (pSIS), 0.91 (pPAS), and 0.90 (pSMRI), significantly outperforming CEA (AUC: 0.85; DeLong test, p < 0.05). LASSO and Boruta algorithms confirmed IL-8, CRP, and galectin-1 as the most critical features. Conclusion: This study demonstrates that inflammatory markers (IL-8, CRP, and galectin-1) statistically mediate 73.8% of the smoking-CRC association, providing strong evidence consistent with, but not proof of, an inflammasome-mediated causal pathway. This study offers a blood test that detects harmful inflammation early, enabling earlier diagnosis and potential targets for prevention. Prospective validation is required to confirm causality.