Abstract 4822: Immunophenotyping circulating tumor cells in patients with unknown primary

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA Metastasis is responsible for the majority of cancer-related deaths. A limiting step in metastasis is access to circulation, thus circulating tumor cells (CTCs) should be present in all patients with metastatic tumors, which may have both diagnostic and prognostic value. Accounting for only 3-5%, carcinoma of unknown primary (CUP) presents a challenge for clinicians in diagnosis and therapy. In 20 to 50% of CUP patients, the primary remains undiagnosed even after a full diagnostic work up. Tissue biopsy is the standard for diagnosis but there is need for improved methodology, including a non-invasive blood test that relies on CTC analysis. Our overall objective is to utilize CTCs to provide insight into systemic cancer progression and approaches to therapy, including a CTC blood test as a tool for diagnosis, prognosis and therapy. We hypothesize that real-time, single-cell immunophenotype profiling of CTC populations will inform diagnosis of tissue of origin, reveal prognostic markers such as stem-like properties and predict tumor aggressiveness. We have been developing a post-Veridex CTC analysis method using multiplexed Q-dot conjugated antibodies with the goal of detecting multiple markers in each single cell within a CTC population to aid in CUP diagnosis including tissue of origin. We have adapted this method for use in CTCs captured using the flexible micro spring array (FMSA) size-based CTC enrichment protocol and other approaches for capturing and immunophenotyping live CTCs. Further adaptation of this protocol enables the use of Dye-Light conjugated primary antibodies. For carcinomas we use cytokeratin 7 (CK7), cytokeratin 20 (CK20), thyroid transcription factor (TTF-1), estrogen receptor (ER; for female patients) and prostate specific antigen (PSA; for male patients) as a minimal set of markers for the identification of lung, colon, prostate and breast cancer. Successful validation of antibodies to these five markers has enabled multiplexing after DyLight conjugation in positive and negative cell lines. This approach is currently being tested in CTCs from patients and is being expanded to understand the biology of CTCs through an evaluation of EMT and stem cell markers. Successful application of our CTC-CUP protocol to CTCs in patient samples is expected to provide a noninvasive, relatively quick and inexpensive blood test that can be both diagnostic and prognostic, which may be a valuable adjunct to routine biopsy. Circulating tumor cells may provide insight into the mechanism of systemic cancer progression, the characteristics of metastatic founder cells and changes within these cells as cancer progresses, thereby impacting the efficacy and evaluation of cancer therapy. Citation Format: Elizabeth M. Matthew, Lanlan Zhou, Bora Lim, Nicholas E. Lamparella, David T. Dicker, Jean-Nicolas Gallant, Monika Joshi, Sheldon L. Holder, Ramdane Harouaka, Siyang Zheng, Joseph J. Drabick, Cristina I. Truica, Zhaohai Yang, Wafik S. El-Deiry. Immunophenotyping circulating tumor cells in patients with unknown primary. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4822. doi:10.1158/1538-7445.AM2014-4822