Abstract A31: CDK4/6 inhibition plus radiotherapy enhances anti-tumor immune responses in non-small cell lung cancer


 Background: Lung cancer is the main cause of cancer-related mortality, of which non-small cell lung cancer (NSCLC) accounts for 85%. Abemaciclib, a selective CDK4/6 inhibitor, enhanced the radiosensitivity of NSCLC in vivo and in vitro and improved the prognosis of advanced NSCLC patients according to a Phase Ⅰ clinical trial. This study aimed to explore the impact of CDK4/6 inhibition combined with irradiation and immunotherapy on NSCLC.Methods: The in vivo xenograft tumor mouse model was used to investigate the synergistic effects of CDK4/6 inhibitor abemaciclib and irradiation together with anti-PD-1 antibodies. The tumor infiltrating lymphocytes (TILs) in tumor microenvironment (TME) were analyzed by flow cytometry. The complete blood count and serum tests were used to determine the safety of this combination therapy. The human phospho-kinase array and dual-luciferase report assay were used to study the regulatory mechanisms of abemaciclib and irradiation combination on PD-L1 transcription in NSCLC cells in vitro.Results: Our results indicated the significantly synergistic effects of abemaciclib, irradiation and anti-PD-1 antibodies on NSCLC growth in vivo, accompanied by increased CD8+ T cell infiltration and decreased regulatory T cells and myeloid-derived suppressor cells (MDSCs), suggesting a strong anti-tumor combination of CDK4/6 inhibition, radiotherapy and immunotherapy. This synergistic effect could be partially impaired by CD8 depletion, and alleviated the anemia and inflammation caused by tumor burden without hepatorenal toxicity. Abemaciclib induced PD-L1 transcription through JNK/c-Jun pathway in vitro, which might elevate PD-L1 expression synergistically with irradiation through TBK1/IRF3 pathway.Conclusions: Our studies suggested that CDK4/6 inhibition plus irradiation enhanced anti-tumor immune responses in NSCLC. Together with immunotherapy, the combination of CDK4/6 inhibitors and radiotherapy could lower the doses of individual treatment, thus alleviating the potential toxicity and side effects of CDK4/6 inhibition and irradiation on normal cells.
 Citation Format: Zhengrong Huang, Hongxin Xie, Mengqin Wang, Conghua Xie, Yan Gong. CDK4/6 inhibition plus radiotherapy enhances anti-tumor immune responses in non-small cell lung cancer [abstract]. In: Proceedings of the AACR Special Conference: Tumor Immunology and Immunotherapy; 2022 Oct 21-24; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2022;10(12 Suppl):Abstract nr A31.