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Martina Angi, Leila Khoja, Bertil Damato, Paul Lorigan, Caroline Dive, Sarah Coupland, Helen Kalirai; Detection of circulating tumor cells in uveal melanoma using the CellSearch® system. Invest. Ophthalmol. Vis. Sci. 2013;54(15):4225.
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© ARVO (1962-2015); The Authors (2016-present)
Circulating tumor cells (CTC) have been identified previously in the peripheral blood of uveal melanoma (UM) patients using either PCR analysis of tumor-associated RNA or immunomagnetic cell-sorting based on the expression of the melanoma associated chondroitin sulphate proteoglycan (MCSP) antigen. Published data, however, vary significantly between groups. The CellSearch® system (Veridex, New Jersey, USA) is the only FDA approved technology for the enumeration of CTC in the clinical setting. The aim of our study was to apply the CellSearch® system for the detection of CTC in UM patients at different stages of disease.
Blood samples from UM patients with and without metastases were prospectively collected prior to treatment and processed according to the CellTracks® Circulating Melanoma Cell (CMC) kit standard protocol. Patients with primary UM were classified either as high (HR) or low (LR) risk of developing metastases on the basis of clinical, histopathological and genetic features of the ocular tumor, and correlations were drawn with CTC number. Additional validation of the expression of the CMC enrichment (CD146) and detection (MSCP) antigens was performed by flow cytometry using directly conjugated immunofluorescence antibodies in 5 UM cell lines (Mel270, 92.1, Omm1, Omm2.3, Omm2.5) grown as adherent and non-adherent cultures.
CTC were detected in 7/13 metastatic (range 1-525), in 5/14 HR (range 1-2) and in 0/6 LR UM patients. The presence of CTC correlated significantly with monosomy 3 (Chi-square, p<0.01) but not with age, sex, tumor dimensions, ciliary body involvement, epithelioid cellularity or mitotic count (all p>0.05). CD146 was detected in >98% of all cell lines and culture conditions, although the fluorescence intensity (FI) varied between cell lines (range18.1-299.1). Expression of MCSP showed a high degree of heterogeneity within and between cell lines. In general, the FI for MCSP was low across all cell lines (range 10.5-37.2).
The CellSearch® system can detect CTC in the peripheral blood of UM patients at different stages of the disease; however, further studies are necessary to establish its clinical value. CD146 appears suitable for UM cell enrichment, while MCSP may not be an optimal antigen for detection. Additional markers, which can be added to the customizable channel present in the CMC kit, are being investigated to further characterize CTC in UM.
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