Abstract SY24-01: High-throughput CTC detection for noninvasive cancer monitoring

Circulating tumor cells (CTCs) provide a noninvasive source of patient-derived material to repeatedly sample cancer cells during the course of therapy, assessing changes in tumor burden, genetic composition, and transcriptional and RNA-based abnormalities. While some CTCs are viable and tumorigenic ex vivo, the majority of these cells die in the circulation, and some localized cancers with vascular invasion appear to shed CTCs long before the initiation of metastatic lesions. CTC detection therefore also offers an opportunity for early cancer detection. Two major technologic hurdles have limited the broad clinical application of CTC analyses: 1) the capture of these rare cells, estimated at approximately one tumor cell per billion normal blood cells in the circulation; and 2) the complex imaging criteria required for scoring rare and heterogeneous tumor cells using antibody-dependent staining. To address the primary challenge of capturing rare CTCs admixed with large numbers of normal blood cells, we have previously described a microfluidic device, the CTC-iChip, capable of high throughput depletion of normal hematopoietic cells, producing an output that is highly enriched for CTCs. This negative-depletion strategy enables isolation of CTCs across most types of cancer, independent of cell surface markers, and it ensures the highest quality of cellular RNA for downstream molecular analyses. To address the secondary challenge of imaging CTCs using accurate and high throughput platforms, we took advantage of the intact cancer cell–derived transcriptome within microfluidically enriched cancer cells to establish digital PCR platforms, capable of highly sensitive, reliable, and robust detection of CTCs from different cancer types. As proof of principle, we tested the application of such a digital CTC detection in patients with hepatocellular cancer, prostate cancer, and melanoma, demonstrating accurate measurement of tumor burden and associated RNA-based alterations and genotypes, as well as cancer cell–derived predictive markers of drug response. Taken together, the digital scoring of CTCs from microfluidically enriched blood cell populations provides a high throughput and highly quantitative platform for serial noninvasive monitoring of cancer. For future early cancer detection applications, the use of intact cancer cells in the circulation as a source of molecular markers may help distinguish invasive from indolent cancers. Citation Format: Shyamala Maheswaran, Mark Kalinich, Irun Bhan, David Miyamoto, Yu Zheng, Xin Hong, Tanya Todorova Kwan, Ravi Kapur, Lecia Sequist, Ryan Sullivan, Aditya Bardia, Richard Lee, David Ting, Mehmet Toner, Daniel A. Haber. High-throughput CTC detection for noninvasive cancer monitoring [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr SY24-01. doi:10.1158/1538-7445.AM2017-SY24-01