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Abstract 2229: PD-L1 is expressed on CD11bhighCD14highHLA-DR+ myeloid cells in the tumor microenvironment of non-small cell lung cancer (NSCLC)

Understanding the immune system of cancer patients is essential for the development of optimal treatment. We analyzed tumor cells and infiltrating immune cells in tumor tissues of NSCLC to determine the type of cells which expressed immune checkpoint molecules and/or their ligands, and compared them to clinicopathological characteristics. To obtain a single cell suspension from the tumor tissues of lung cancer patients, each fresh tumor sample was chopped and treated with collagenase and DNase. The dissociated tumor tissue cells (DTCs) were stained with fluorochrome-labeled mAbs and the distribution of immune cell components and expression of surface markers in DTCs were determined by FACSuite analysis. The yield of DTCs was 5.87±4.73×10⁁7/gram. PD-L1, which is a ligand for immune checkpoint molecule PD-1, is expressed on CD11bhigh myeloid cells in the blood, regardless of HLA-DR expression. On the other hand, PD-L1 is expressed on CD11highCD14highSSClow myeloid cells in the tumor site. All PD-L1 expressing cells were positive for HLA-DR, a ligand for a T cell receptor of CD4 T cells. Furthermore, these cells also expressed both CD86 and CD124. Interestingly, most tumor cells expressed very low levels of the PD-L1 molecule. And we found that CD11highCD14+HLA-DR- myeloid cells did not express PD-L1. The proportion of CD11highCD14+HLA-DR-PD-L1- myeloid cells was higher in advanced stage patients than early stage patients. In conclusion, PD-L1 is expressed on CD11bhighCD14highHLA-DR+SSClow myeloid cells, but not CD11bhighCD14+HLA-DR- myeloid cells. We propose that the PD-L1+ myeloid cells are likely to play an important role in tumor immunity. Further functional studies will be necessary to determine how the interaction between the cells will affect immunity.
 Citation Format: Chung-Hee Sonn, Yunji Oh, Tae Eun Kim, Jung Sun Ha, Hong Kwan Kim, Jong Ho Cho, Sumin Shin, Jhingook Kim. PD-L1 is expressed on CD11bhighCD14highHLA-DR+ myeloid cells in the tumor microenvironment of non-small cell lung cancer (NSCLC). [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2229.