Characterizing PD-L1 expression in tumor-associated cells and CTC using IncellDx and Celsee molecular diagnostic technologies

Abstract Detection of PD-L1 expression in NSCLC cancer patients is increasingly becoming a widely used molecular diagnostic tool. Evidence also suggests that PD-L1 can be induced with radiotherapy and may be an immune escape mechanism in cancer. Current methods analyze PD-L1 expression in either solid tumor biopsies or circulating tumor cells (CTC), independent of each other. In order to design a comprehensive PD-L1 treatment regime, it is imperative to look at the PD-L1 expression in cancer cells of the tumor as well as in CTCs. In this study we present a comprehensive profiling of PD-L1 expression in solid tumor biopsy and CTC of 10 lung cancer patients. We further extend the study by evaluating the co-relation of the PD-L1 expression with other immune cell infiltration markers in the lung biopsy samples. There is no single technology that can provide a comprehensive profiling of PD-L1 expression in lung biopsies as well as the CTCs isolated from the peripheral blood. Using two very different and unique molecular diagnostic technologies, IncellDx OncoTect iO Single Cell Quantitative PD-L1 assay and automated CTC analysis Celsee C-PREP GENESIS, we present the first report discussing the PD-L1 expression in tumor cells of the solid and liquid biopsies and its correlation with DNA content and infiltrating immune cell markers. Nine out of the ten patient samples evaluated showed strong correlation between DNA content and PD-L1 expression in tumor-associated cells and CTC. One aneuploid patient sample showed very low expression of PD-L1 in tumor-associated cancer cells; however, it still showed a positive staining for PD-L1 in CTC. Obtaining a comprehensive PD-L1 expression and associated immune cell marker profile in solid tumor biopsy and circulating tumor cells may be needed to design a more effective and lasting immunotherapy to treat NSCLC lung cancer patients. The results discussed in this study will strongly impact the current understanding and implementation of the molecular diagnostics tools to evaluate cancer patients in order to define a robust therapeutic regimen. Citation Format: Fariba Fazeli, Vishal Premdev Sharma, William Chiro Chow, Amanda Chargin, Priya Gogoi, Kalyan Handique, Bruce Patterson. Characterizing PD-L1 expression in tumor-associated cells and CTC using IncellDx and Celsee molecular diagnostic technologies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 635.