Hypoxia-Associated Alternative Polyadenylation of CARM1 and Tumor Microenvironment Alterations in Non-Small Cell Lung Cancer

Background: Tumor hypoxia in non-small cell lung cancer (NSCLC) promotes malignant progression and treatment resistance by enhancing abnormal vasculature, invasiveness, and metastasis. However, the molecular mechanisms underlying hypoxia-driven tumor progression remain incompletely understood. Methods: In this study, patient samples, cell lines, single-cell transcriptomic data, and spatial transcriptomic data were comprehensively analyzed to investigate hypoxia-associated molecular alterations in NSCLC. Results: A global trend toward shortened 3’ untranslated regions (3’UTRs) was observed in hypoxic tumors. Analysis of hypoxia-related alternative polyadenylation (APA) events revealed preferential usage of proximal polyadenylation sites (poly(A) sites, PASs) in CARM1. Shortening of the CARM1 3’UTR was associated with hypoxia and may serve as a candidate biomarker. This APA event may reduce putative microRNA (miRNA) binding sites and contribute to increased CARM1 expression, while potentially influencing the expression of hypoxia-related genes such as SELENBP1. Drug sensitivity analysis further suggested that patients with shorter CARM1 3’UTRs may exhibit differential responses to cisplatin chemotherapy. Moreover, single-cell and spatial transcriptomic analyses demonstrated enhanced interactions between hypoxic tumor cells and fibroblasts, highlighting a potential role for APA in remodeling the hypoxic tumor microenvironment. Conclusions: Our findings identify hypoxia-related APA features and characterize hypoxia-associated alterations within the NSCLC tumor microenvironmen, providing new insights into the molecular landscape of hypoxia-associated tumor progression.