Fusion gene recurrence in non-small cell lung cancers and its association with cigarette smoke exposure.

Background: Lung cancer remains the leading cause of cancer-related deaths in the US despite novel treatment protocols, with about 235,000 new cases and 131,000 deaths expected from this cancer in 2021 alone. Lung adenocarcinoma and squamous cell carcinoma, which are both subtypes of non-small cell lung cancer, account for most lung cancer cases, and comparing the molecular signatures in these two cancers can identify novel mechanisms that contribute to non-small cell lung cancer oncogenesis. Methods: We, in this study, performed a comprehensive gene fusion profiling of these cancers, which is understudied in lung cancers. Using an alignment-free fusion detection tool, 'ChimeRScope', we screened for gene fusions in lung adenocarcinoma and squamous cell carcinoma datasets from The Cancer Gene Atlas database. Fusion profiles in these two cancer subtypes were essentially different with minimal overlap. Results: Our analysis revealed a positive association of smoking to fusion frequency in lung adenocarcinoma but not in squamous cell carcinoma and identified several fusion genes that could be explored as markers associated with cigarette smoke exposure. We also identified differentially regulated pathways linked to E2F, G2M checkpoint, and MTORC1 signaling upregulated and P53 pathway downregulated in samples containing high fusions in lung adenocarcinoma. Our results indicate that downregulation of the P53 pathway leads to higher gene fusion formation in lung adenocarcinoma. Conclusions: This manuscript provides a strong rationale for investigating the molecular mechanisms of cigarette smoke-induced gene fusion formation associated with lung cancer. Novel recurrent fusions associated with cigarette smoke were identified in our study, which could further be investigated for patient stratification, personalized therapy, and therapeutic monitoring.