Simple Summary The impact of smoking on the development of lung cancer is widely acknowledged; however, all of the molecular processes behind this effect, as well as their possible clinical applications, are still unclear. The current study aimed to identify and describe a potential smoking-related molecular mechanism in squamous cell lung cancer, with its possible connection to the immunotherapy response. By analyzing bioinformatic data from different databases and conducting experiments on clinical tumor samples, we demonstrated the connection between the microRNA mir-301a and the transcription factor IRF1, which demonstrated the capacity to affect many immune pathways in lung cancer and the efficacy of treatment with immune checkpoint inhibitors. These findings not only clarify certain molecular characteristics of squamous cell lung cancer but also open up new avenues for future immunotherapy research.Abstract Smoking is an established risk factor for a variety of malignant tumors, the most well-known of which is lung cancer. Various molecular interactions are known to link tobacco smoke exposure to lung cancer, but new data are still emerging on the effects of smoking on lung cancer development, progression, and tumor response to therapy. In this study, we reveal in further detail the previously established association between smoking and hsa-mir-301a activity in lung squamous cell carcinoma, LUSC. Using different bioinformatic tools, we identified IRF1 as a key smoking-regulated target of hsa-mir-301a in LUSC. We further confirmed this relationship experimentally using clinical LUSC tissue samples and intact lung tissue samples. Thus, increased hsa-mir-301a levels, decreased IRF1 mRNA levels, and their negative correlation were shown in LUSC tumor samples. Additional bioinformatic investigation for potential pathways impacted by such a mechanism demonstrated IRF1's multifaceted role in controlling the antitumor immune response in LUSC. IRF1 was then shown to affect tumor immune infiltration, the expression of immune checkpoint molecules, and the efficacy of immune checkpoint blockade therapy. As a result, here we suggest a smoking-regulated mir301a/IRF1 molecular axis that could modulate the antitumor immune response and immunotherapy efficacy in LUSC, opening up novel opportunities for future research.
