Introduction Prostate cancer is the second leading cancer among men in the world and known as the most frequently diagnosed cancer in more than half of countries with estimated 1.3 million new emerging cases. Because of low specificity of serum PSA screening for prostate cancer, it raised concerns in keep management of clinical prognosis and therapeutic decision and thereby, there are still needed precise real-time biomarkers. Many recent studies have reported that circulating tumor cells (CTCs) can be used as important biomarkers for prostate cancer at cellular and molecular levels. However, due to their extreme rarity in the circulatory system and the lack of technology to isolate them precisely, it is still difficult to isolate them with high purity and efficiency that can be applied for clinical purposes. In this study, we introduce a microfluidic technology using lateral magnetophoresis for isolating CTCs from blood of prostate cancer patients (n=62) with high purity and efficiency and demonstrate clinical usefulness of isolated CTCs at cellular and molecular levels.

Materials and methods By the lateral magnetophoretic technology using immunomagnetic nanobeads, highly pure CTCs were isolated from 5 ml blood, drawn from patients with localized (n=25) and metastatic (n=37) prostate cancer. Then, prostate cancer related genes (AR, AR-V7, EpCAM, KRT-19, PSA and PSMA) were quantified by droplet digital PCR (ddPCR) method using mRNA in CTCs.

Results and discussion CTCs were detected from all blood samples (n=62). In localized cases, the average number of isolated CTCs and purity were 6.58 per ml and 2.09%. In metastatic cases, the average number of isolated CTCs and purity were 27.55 per ml and 6.00%, higher than those of localized cases. Then, mRNA was extracted from isolated CTCs and used for detecting prostate cancer specific genes. Their detection rate and expression level were increased from localized to metastatic stages. AR was detected at a similar rate of 76.00% in both localized and mHSPC stages and increased to 100% in mCRPC stage. AR-V7 was detected only in metastatic stages, mainly in mCRPC stages. EpCAM showed the highest detection rate in all stages, such as 96.00% in localized, 88.89% in mHSPC and 100% in mCRPC. This result indicates that CTCs are isolated from all blood of patients. KRT-19 showed slightly lower detection rate than EpCAM, but tend to be similar to EpCAM expression for cancer stages. PSA and PSMA were expressed very high in metastatic stage. PSA expression level in metastatic stage was 198.28 times higher than that in localized stage. Interestingly, the expression of PSA mRNA measured from CTCs was linearly proportional to serum PSA protein level, which is a commonly used diagnostic biomarker for prostate cancer.

Conclusions In all stages of prostate cancer patients, the proposed microfluidic technology using the lateral magnetophoresis is a high-performance method for isolating CTCs with high detection rate and purity that can be used for precision genetic analysis.

Citation Format: Hyungseok Cho, Ki-Ho Han, Jae-Seung Chung. Highly effective isolation of circulating tumor cells using lateral magnetophoretic technology for precise genetic analysis of prostate 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 774.