Abstract 1469: Specific detection tool for mesenchymal and epithelial-mesenchymal transformed circulating tumor cells.
Authors: Satelli Arun , Mitra Abhisek , Cutrera Jeffery J. , Xeuqing Xia , Denada Dibra , Chelouche Dina Lev , Overman Michael James , Lee Ellis , Li Shulin 
Published: August 2014

Circulating tumor cells (CTC) released from primary tumor tissues into bloodstream or lymphatic vessels are emerging as novel tools in the detection and prognosis of several types of metastatic cancers. At present, CTC markers are limited to epithelial cancers and there are no specific markers available to detect mesenchymal and epithelial-mesenchymal transformed (EMT) CTCs. EMT cells are characterized by increased motility and invasiveness and are known to escape detection technologies that use EpCAM and cytokeratins as CTC markers. Here we report a novel antibody, 84-1 for detection of mesenchymal and EMT CTC. Antibodies were raised in mice after injecting metastatic cancer cells and clones were selected that were positive only for CTC and negative for PBMCs and normal cells. 84-1 was the only antibody that was unique in its ability to detect CTCs from mesenchymal tumors and EMT CTC from epithelial tumors. Studies for characterization of the epitope for 84-1 antibody are ongoing. We then analyzed the sensitivity and specificity of the antibody by utilizing spiking assay and were able to specifically detect and isolate as low as one cell from 1 ml of blood. In a pilot analysis, we were able to detect CTCs from patients with colon cancer, hepatocellular carcinoma, osteosarcoma, and leukemia with very high specificity, while CTCs were not observed in healthy subjects. CTCs were characterized based on the size of the nucleus and for 84-1 positivity and CD45 negativity using fluorescence microscopy. The CTCs from cancer patients were isolated and cultured for mutational analysis. CTCs were also detectable in the blood of mice with tumors of both epithelial (colon) and non-epithelial (osteosarcoma) origin and were isolated and cultured in vitro, which formed colonies of cells that were used for further analysis to confirm the identity of CTCs. Furthermore, we also evaluated CTCs in mutant p53 mice that developed spontaneous tumors of both mesenchymal and epithelial origin. Collectively, our observations provide a novel technology to selectively detect and isolate both mesenchymal and EMT CTC. Detection and molecular characterization of CTCs is one of the fastest growing areas of translational cancer research. Utilizing our antibody, we can enumerate and isolate rare CTCs that will aid in the early detection of tumors, metastasis, and relapse and will contribute to the development of specific targeted therapies, an ultimate goal of personalized medicine.

Citation Format: Arun Satelli, Abhisek Mitra, Jeffery J. Cutrera, Xia Xeuqing, Dibra Denada, Dina Lev Chelouche, Michael James Overman, Ellis Lee, Shulin Li. Specific detection tool for mesenchymal and epithelial-mesenchymal transformed circulating tumor cells. [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 1469. doi:10.1158/1538-7445.AM2013-1469