POR and squamous cell lung carcinoma: As shown in forest plots (Figs. 7A, B), these 7 genes show highly consistent causal effect directions on RA and squamous cell lung cancer risk (for example, POR and EIF3CL are risk factors for both diseases, while ANTXR2 is a protective factor for both), indicating they are key genetic nodes connecting the pathophysiological processes of both diseases.