Abstract B21: Circulating tumor cell by microfluidic magnetophoresis-based gene expression changes for monitoring of prognosis in advanced prostate cancer patient: A pilot study

Abstract Introduction: By using the circulating tumor cells (CTCs), we can get useful genomic information that enables monitoring of patients’ prognosis or selecting appropriate treatment over time by repeat biopsy. The aim of this study is to separate CTCs from prostate cancer patients using new microfluidic technique that is based on disposable lateral magnetophoretic microseparator and to assess the gene expression that is specific for prostate cancer using mRNA from isolated CTCs measured by droplet digital PCR (ddPCR) method. We also evaluated the treatment-dependent gene-profile changes in four metastatic castration-resistant prostate cancer patients (mCRPC). Patients and Methods: Total 55 samples of 49 patients who underwent treatment for prostate cancer between 06/2018 and 05/2019 were prospectively enrolled. Approximately 10 mL of whole blood was drawn from prostate cancer patients; Group A, 14 samples (25.4%) with localized stage II-III cancer; Group B, 5 samples (9.1%) with stage IV; Group C, 8 samples (14.5%) with metastatic hormone-sensitive prostate cancer (mHSPC); and Group D, 29 samples (52.7%) with mCRPC. In particular, more than two repeated blood collections were performed for 4 mCRPC. CTCs were positively isolated by using assembly-disposable CTC-μChip. CTCs from 5 mL of blood were used for counting to identify isolated CTC numbers with immunofluorescence detection procedure. CTCs from the remaining 5 mL of blood were used for gene analysis by ddPCR for 6 prostate cancer-related genes, such as androgen receptor (AR), androgen receptor splice variant 7 (AR-V7), prostate specific membrane antigen (PSMA), prostate specific antigen (PSA), cytokeratin-19 (CK-19), and epithelial cell adhesion molecule (EpCAM). Results: We identified the average of 3, 16, 14, and 26 CTCs per 1ml in group A, B, C, and D, respectively (P< 0.01). The gene positive rates of AR, AR-V7, KRT-19, EpCAM, PSA, and PSMA were 85.4% (47/55), 16.4% (9/55), 56.4% (31/55), 92.7% (51/55), 41.8% (23/55), and 50.9% (28/55), respectively. The copy number of PSA, PSAM, and KRT-19 increased in proportion as the clinical stage increased. 92.7% of samples showed EpCAM positive, whereas AR-V7 was a rare event, with only in 9 out 28 samples positive with mCRPC, but not in other stages. In particular, of the four mCRPC patients who repeated blood sampling, the number of CTCs and the expression of AR, PSA, PSMA, and KRT-19 decreased in patients who responded to drug (enzalutamide and docetaxel). On the other hand, patients who were resistant to drug showed increased expression of AR-V7 and KRT-19 with the increased number of CTC. Conclusions: This study demonstrated that CTC-based multigene profiling could be analyzed using ddPCR. We have also identified several genes associated with progression in mCRPC patients initiating enzalutamide or chemotherapy. While this is a pilot study and prospective validation is needed, these findings highlight the potential role for this approach in real-time monitoring of advanced prostate cancer patients. Citation Format: Jae-Seung Chung, Hyungseok Cho, Ki-Ho Han. Circulating tumor cell by microfluidic magnetophoresis-based gene expression changes for monitoring of prognosis in advanced prostate cancer patient: A pilot study [abstract]. In: Proceedings of the AACR Special Conference on Advances in Liquid Biopsies; Jan 13-16, 2020; Miami, FL. Philadelphia (PA): AACR; Clin Cancer Res 2020;26(11_Suppl):Abstract nr B21.