Abstract 471: Detection of circulating tumor cells in high-risk primary uveal melanoma by the photoacoustic method
Authors: Weight Ryan M. , Sato Shingo , Ohara Masahiro , Terai Mizue , Mastrangelo Michael , Orloff Marlana , Goldschmidt Benjamin , Viator John , Sato Takami 
Published: July 2016

Abstract
Circulating tumor cells (CTCs) have been shown to be a prognostic marker in breast cancer1. We hypothesize that circulating melanoma cell (CMC) detection could be utilized in the management of uveal melanoma, including early intervention. Prior methodologies for circulating uveal melanoma cell (CUMC) detection have been fraught with poor sensitivity, limiting their clinical utility2. Development of an improved method is necessary to establish the clinical utility of CUMC monitoring. Photoacoustics, also referred to as laser-induced ultrasound, is a novel platform for the detection and capture of CMCs. Photoacoustics uses short duration pulsed light to create ultrasonic acoustic waves in an optically absorbing medium, in this case melanin within melanoma3. As light is absorbed by irradiated chromophores, the optical energy gets converted into kinetic thermal energy trapped within the chromophore and subsequent thermal expansion ensues. Transient thermoelastic expansion of the absorbent cell results in the propagation of ultrasonic acoustic waves which can be detected and analyzed using a piezoelectric response mechanism. In addition, detected CMCs can be isolated by a two-phase flow cell separation technique4. Due to the low cost and melanoma specific capabilities of photoacoustics, we evaluated this technology for the purpose of CUMC detection. Methods: Cells from uveal melanoma cell line UM002B, established at Thomas Jefferson, were titrated to various cell concentrations and analyzed in a neutral density solution utilizing the photoacoustic method. Uveal melanoma cells of differing concentrations were spiked into isolated healthy donor peripheral blood mononuclear cells (PBMCs) and healthy whole blood samples. PBMC isolates were analyzed for CUMCs. Results: CUMCs were successfully quantified by the photoacoustic method including single cell detection. Recovery rates of cultured cells in a neutral density solution approached 25%. Recovery rates for CUMCs in whole blood averaged 10% of expected cell yield (56/540 cells detected) with a higher detection rate at lower cell concentrations. Photoacoustics offers a viable method for the detection of CUMCs with an accuracy that meets or exceeds previously reported CUMC yields. Studies analyzing CUMCs from patients with metastatic disease are ongoing.
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3. Weight RM, et al. Photoacoustic detection of metastatic melanoma cells in the human circulatory system. Opt Lett. 2006 Oct 15;31(20):2998-3000.
4. O’Brien CM, et al. Capture of circulating tumor cells using photoacoustic flowmetry and two phase flow. J Biomed Opt. 2012 Jun;17(6):061221.
Citation Format: Ryan M. Weight, Shingo Sato, Masahiro Ohara, Mizue Terai, Michael Mastrangelo, Marlana Orloff, Benjamin Goldschmidt, John Viator, Takami Sato. Detection of circulating tumor cells in high-risk primary uveal melanoma by the photoacoustic method. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 471.