Abstract 5368: A multiparameter assay for HER2 protein detection on circulating tumor cells in non-small cell lung cancer

Abstract

Abstract Lung cancer biopsy can be difficult to perform successfully; it has a 30% adverse event risk and often provides insufficient material to test. Therefore, a liquid biopsy method to analyze the tumor is advantageous. Analysis of circulating tumor cells (CTCs) by multiparameter immunofluorescence (IF) microscopy allows non-invasive characterization of cancer cell biomarker expression. HER2 is a well-known therapeutic target in breast cancer and studies have shown that HER2 status on CTCs may provide prognostic information about response to anti-HER2 therapies. Less is understood about its frequency and clinical importance in non-small cell lung cancer (NSCLC). The RareCyte platform is uniquely suited for CTC identification and phenotypic characterization with a sensitive, accurate, simple and repeatable workflow from blood collection to CTC characterization and single-cell isolation. We developed an assay for detecting HER2 expression on lung CTCs using the RareCyte platform and validated the assay on model CTC spike-in samples with high (BT-474), medium (MDA-MB-453), low (H1650 and OVCAR-3) and absent (MDA-MB-468) HER2 protein levels. Blood was processed to slides using the AccuCyte Sample Preparation System and stained with anti-HER2 together with the RarePlex Kit for CTC identification (nuclear dye, anti-CD45 to exclude WBC, and anti-cytokeratin/EpCAM for CTCs). The spike-in samples showed the expected trend in per-cell HER2 mean fluorescence intensity values. The percentage of HER2-positive cells was > 90% for the HER2-high, medium and low cell lines, and < 5% for the HER2-negative cell line. The assay was applied to 10 advanced stage (III or IV) post-treatment NSCLC patient samples. At least 1 CTC was found in 6 samples (range 0-2043) and HER2 expression was confirmed in 5 out of the 6 samples, indicating this assay is useful for characterizing HER2 expression in CTCs in NSCLC. Citation Format: Edward Lo, Daniel Campton, Lillian Costandy, Heather Itamoto, Ryan Huston, Braden Gardner, Steve Reese, Arturo Ramirez, Eric P. Kaldjian, Tad George, I-Ming Wang, Steven Pirie-Shepherd. A multiparameter assay for HER2 protein detection on circulating tumor cells in non-small cell lung cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5368.