RNF200 enhances radiotherapy sensitivity by modulating PD-L1 stability in tumor-associated macrophages of lung cancer.

Radiotherapy is a cornerstone treatment for lung cancer; however, enhancing its efficacy and overcoming immune escape mechanisms - particularly those mediated by tumor-associated macrophages (TAMs) expressing programmed death-ligand 1 (PD-L1) - remain significant challenges. The E3 ubiquitin ligase RNF200 has been implicated in the regulation of PD-L1 expression, yet its role in the context of radiotherapy is not well understood. To address this, non-small cell lung cancer (NSCLC) tissue samples from patients with and without prior radiotherapy were analyzed for RNF200 and PD-L1 expression using quantitative RT-PCR and Western blotting. Additionally, RAW264.7 macrophages were subjected to ionizing radiation and genetically manipulated to assess the impact of RNF200 on PD-L1 expression and stability through co-immunoprecipitation and ubiquitination assays. Co-culture experiments with macrophages and lung cancer cells were performed to evaluate the influence of RNF200 on radiotherapy sensitivity. In NSCLC tissues and macrophages, radiotherapy was found to downregulate RNF200 expression while upregulating PD-L1 expression. Overexpression of RNF200 led to marked suppression of PD-L1 expression, whereas RNF200 knockdown produced the opposite effect. Co-immunoprecipitation and ubiquitination assays revealed that RNF200 physically interacted with PD-L1 and promoted its polyubiquitination and proteasomal degradation. Furthermore, co-culture studies demonstrated that macrophages overexpressing RNF200 enhanced the sensitivity of lung cancer cells to radiotherapy, as evidenced by reduced proliferation, increased necrosis, and decreased secretion of transforming growth factor beta TGF-β. Collectively, these findings indicate that RNF200 enhances radiotherapy sensitivity in lung cancer by regulating PD-L1 expression through ubiquitination. Targeting RNF200 may represent a promising strategy to improve the efficacy of radiotherapy in lung cancer treatment.