Altering the dendritic cell signature in the lung: a new adjuvant to immune checkpoint inhibitor therapies?

Abstract

Abstract Lung cancer is the leading cause of cancer-related death. While the recent introduction of immune checkpoint immunotherapies significantly improves patient outcome, many do not respond to this treatment. Dendritic cells (DCs) activate CD8+ T cells to promote the anticancer immune response. Also, in mice, pulmonary CD103+ DC1s specialize in tumour antigen presentation. However, cancer induces an immunosuppressive microenvironment that alters immune function to promote tumor development. Yet, the impact of lung tumor development on DCs remains misunderstood. To study the impact of lung tumour development on the lung dendritic cell signature, Lewis lung carcinoma (LLC) and B16F10 cells (melanoma lung metastasis) were injected intravenously, and lung DC populations analysed by flow cytometry. We observed that in cancer, the proportions of CD103+ DC1 are largely reduced, while an uncharacterized lung CD103+CD11b+ DC population is induced. The latest express surface markers and transcription factors associated with the DC2 population and high levels of PD-L1 and PD-L2 regulatory molecules. This is of crucial importance to immune checkpoint inhibitor therapies, as they rely on the efficient presentation of tumour antigen by DCs to induce T cell responses. In order to promote the anti-tumor capacity of the DC signature, CD103+ DC1s were injected in combination with an immune checkpoint inhibitor (anti-PD-1) in the B16F10 model of resistance to anti-PD1 therapy. The co-injection led to improved sensitivity to immunotherapy. Thus, promoting the replenishment of an anticancer DC environment could be an interesting therapeutic avenue to increase the efficiency of existing immune checkpoint inhibitor therapies.