Abstract 6684: Detection of PD-L1, HER2 and EGFR on circulating tumor cells in carcinoma patients
Authors: Khandare Jayant , Bharde Atul , Jayant Sreeja , Aland Gourishankar , Garbhe Meghana , Gosavi Sayali , Janorkar Apoorva , Tikekar Purva , Patil Mrunmayi , Jadhav Vikas , Khutale Ganesh , Ashturkar Amrut , Vasudevan Aravindan , Prabhash Kumar , Raut Nirmal , Chaturvedi Pankaj 
Published: April 2023

Abstract
Background: Small molecular inhibitors and immunotherapy has emerged as a novel alternative treatment regime for a variety of epithelial cancers. Large number of clinical trials are in progress to gauge efficacy of tyrosine kinase inhibitors or immune checkpoint inhibitors against actionable targets such as receptor tyrosine kinases and program death ligand 1 (PD-L1). Although highly effective, the outcome of PD-L1 based ICI or TKI against RTKs is vitally contingent on the presence of PD-L1 or RTK expression on circulating tumor cells. We report validation of CTCs with PD-L1, HER2 and EGFR expression in different epithelial cancers.
Methods: We retrospectively evaluated 134 carcinoma patients blood for presence of CTCs expressing PD-L1, HER2 or EGFR markers respect. 45 % patients had lung cancer, while 25 % and 20 % were presented with breast and GI and CRC malignancies. Remaining were gallbladder, ovarian, prostate, and head and neck cancers. CTCs were isolated from DCGI approved OncoDiscover platform with immunomagnetic targeting of EpCAM. CTCs were confirmed with expression of CK18, absence of CD45 and presence of DAPI nucleus. Presence/absence of biomarkers was determined using fluorescence imaging. Expression of PD-L1, HER2 or EGFR was detected by fluorescence microscopy using fluorescently labelled anti PD-L1, HER2 or EGFR antibodies respect. Based on fluorescence intensity CTCs were binned as PD-L1, HER2 or EGFR negative for no detectable fluorescence signal or weakly or strongly positive based on low or high fluorescence signal.
Results: Among the evaluated cohort, 51% of CTCs showed presence of PD-L1 expression. While 63% showed HER2 positive CTCs (breast cancer). 20% from the PD-L1 positive population showed stronger PD-L1 expression. 78% of CTCs from lung cancer patients showed presence of detectable PD-L1 signal, while 66% breast, GI and CRC patients showed CTCs with PD-L1 expression. CTCs from HNC and gall bladder cancer patients showed low PD-L1 expression (25% and 50% respect.). Among CTCs originating from different cancer types, breast cancer CTCs showed higher mean expression of PD-L1 compared to CTCs from CRC patients. A clear subset of CTCs for PD-L1 and Her2 expression was observed in lung and breast cancer patients respect, suggesting the heterogeneity in expression or presence of different subclones within the same tumor type. CTCs evaluated for EGFR expression, 50% showed presence of detectable EGFR compared to the cut-off signal.
Conclusions: CTC can be used as a real-time surrogate for molecular profiling of PD-L1, HER2 and EGFR expression. These CTC cell surface markers offer alternative for immunotherapy or targeted therapies decisions in a adenocarcinomas.
Citation Format: Jayant Khandare, Atul Bharde, Sreeja Jayant, Gourishankar Aland, Meghana Garbhe, Sayali Gosavi, Apoorva Janorkar, Purva Tikekar, Mrunmayi Patil, Vikas Jadhav, Ganesh Khutale, Amrut Ashturkar, Aravindan Vasudevan, Kumar Prabhash, Nirmal Raut, Pankaj Chaturvedi. Detection of PD-L1, HER2 and EGFR on circulating tumor cells in carcinoma patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6684.