Abstract 1460: Quantification of circulating tumor cells using multiplexed Surface-Enhanced Raman Scattering Nanoparticles.

Background: Detection, quantification, and molecular characterization of CTCs may aid physicians in treatment decision making and optimizing. However, the major challenge in the detection and characterization of CTCs is the lack of a highly specific and sensitive assay to isolate and identify the rare population of CTCs in complex blood samples. Moreover, current approaches for CTC detection including CellSearch (FDA approved CTC detection method) which primarily relays on single biomarker are suboptimal because of tumor heterogeneity. Here we develop a multiplexed single-tube assay for directly detection of CTCs in blood sample using two targeted Surface-Enhanced Raman scattering (SERS) nanoparticles. Methods: SERS nanoparticles (60 nm) were prepared by spectral encoding with a Raman reporter molecule (QSY or BHQ) and then stabilized and protected by low molecular weight polyethylene glycols (PEGs). A targeting ligand, epidermal growth factor (EGF) peptide or epithelial cell adhesion molecule (EpCAM) antibody, was covalently conjugated to PEG layer of SERS nanoparticle. The functionalized EGF- or EpCAM- SERS nanoparticle was able to identify CTCs in the peripheral blood with high specificity and affinity. Results: We collected and examined fresh blood samples from 20 SCCHN patients with various histologies and successfully detected positive SERS signals that were greater than background in 9 of 12 (75%) of patients. This technique was demonstrated to be capable of identifying rare CTCs by two biomarkers simultaneously, with a range of 5-720 cells per ml of whole blood. Blood samples from 3 normal controls did not show any CTCs. In one patient who had 0 count of CTC detected by EGFR-targeting SERS tag showed 170 CTCs/ml of blood detected by EpCAM-targeting SERS tags. Conclusion: Special design of the two SERS nanoparticles, distinguished with unique spectral signatures and bio-conjugation of EGF or EpCAM antibody as targeting molecule, allowed simultaneous detection of epidermal growth factor receptor (EGFR) or EpCAM on CTCs in one blood sample. Our technique based on two biomarkers rather than those relayed on single biomarker may improve CTC assessment in clinical settings. (This research was supported by the National Cancer Institute award 5 P50 CA128613 and U54CA119338-04). Citation Format: Xu Wang, Ximei Qian, Jonathan J. Beitler, Zhuo (Georgia) Chen, Fadlo R. Khuri, Melinda M. Lewis, Hyung J. Shin, Shuming Nie, Dong M. Shin. Quantification of circulating tumor cells using multiplexed Surface-Enhanced Raman Scattering Nanoparticles. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1460. doi:10.1158/1538-7445.AM2013-1460