Abstract 629: Label-free isolation of circulating tumor cells for cytomorphological analysis
Authors: Renier Corinne , Pao Edward , Go Derek E. , Che James , Rao Jianyu , Rao Nagesh , Garon Edward , Goldman Jonathan , Kulkarni Rajan P. , Jeffrey Stefanie S. , Sollier Elodie , Di Carlo Dino 
Published: August 2015

INTRODUCTION: The isolation of circulating tumor cells (CTCs) from the bloodstream is a promising tool for improving cancer prognosis, targeted therapies, and to understand the biology of metastatic processes. CTC analysis could benefit from conventional cytology staining procedures and cytopathologist expertise in classifying malignant cells from body fluids, to monitor CTC levels in patients in a low-cost system. However, CTCs are very rare with usually only 1-10 CTCs per mL of blood, which limited their use by cytopathologists in the past. Many current approaches for CTC isolation lead to high backgrounds of non-malignant cells (low purity) and/or capture over large areas, which are difficult to analyze microscopically.

METHODS: Vortex is a label-free approach for rare malignant cell enrichment from bodily fluids. This technology requires no prior sample preparation, is cost effective and able to deliver viable and pure cells in a small volume. 21 blood samples were processed through our Vortex device. Larger CTCs are trapped within an array of micro-scale fluid vortices that form in simple rectangular reservoirs, while smaller erythrocytes and leukocytes pass through. The tumor cells are released into a small volume of buffer (&lt; 500uL) and collected directly on a chamber slide for fixation and cytological staining using cytopathology standard operating procedures. After Papanicolaou staining, the slides are examined by cytopathologists.

RESULTS: Our CTC collection method was optimized to reduce the loss of rare atypical cells during the cytology procedure (&gt;70% cell recovery), improve the cytological staining quality (defined as good by cytopathologists), with an overall fast workflow (&lt;12H). The collection protocol was designed to be cost-effective, and compatible with commercially available reagents and consumables to facilitate the broad use of our platform by research and clinical labs. Atypical cell populations were isolated by Vortex and identified through conventional Papanicolaou staining in the blood of 15/16 patients with metastatic lung (N = 10) and breast cancer (N = 6). No atypical cells were identified in the blood of 5/5 healthy donors. For 2 lung cancer patients, similar morphological features were seen in the corresponding primary tumors.

CONCLUSION: Vortex CTC enrichment is compatible with existing cytology staining and analysis procedures, with significant advantages in terms of processing time, low cost, simplicity, cell integrity and purity. The detection of atypical cells in 15/16 metastatic cancer patient blood samples demonstrates the utility of Vortex enrichment combined with cytological staining as a non-invasive and cost effective method to monitor disease progression and help guide clinical decision-making.

Citation Format: Corinne Renier, Edward Pao, Derek E. Go, James Che, Jianyu Rao, Nagesh Rao, Edward Garon, Jonathan Goldman, Rajan P. Kulkarni, Stefanie S. Jeffrey, Elodie Sollier, Dino Di Carlo. Label-free isolation of circulating tumor cells for cytomorphological analysis. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 629. doi:10.1158/1538-7445.AM2015-629