Abstract 5248: Quantum dot multiplexing of prognostic marker and stem cell marker expression in colorectal cancer circulating tumor cells

Abstract

Abstract Circulating tumor cells (CTCs) reflect disease burden in metastatic colorectal cancer (mCRC) and show reduced numbers in patients who are responding to chemotherapy. Current analysis is limited to counting CTCs and little additional marker analysis. We sought to develop methodology to allow multiplexing of marker detection in individual CTCs to assess tumor cell heterogeneity and to gain insight into relationships of prognostic and therapy response markers. This ongoing study is evaluating expression of up to 8 markers in a single CTC by a multispectral multiplex imaging technique using nano-particle type quantum dot (Q-Dot) dyes. We hypothesize that CTCs that are extremely rare (∼ 1 in 10 million RBCs) in the blood of cancer patients play an important role in metastasis. In view of the small number of such cells in the blood of mCRC patients (prognostication based on <3 versus >3 CTCs/7.5 ml of blood) there is a need to derive more molecular correlations from single CTCs. We designed a clinical protocol to collect blood from mCRC patients receiving chemotherapy with the intent to evaluate multiplexed molecular marker expression in CTCs in responders versus non-responders using the FDA-approved Veridex CellSearch technology. We are evaluating CD26, CD133, EGFR, Ki 67, p27, c-Myc, ALDH1, Bcl-Xl, Mcl-1, phosho-Akt, phospho-ERK, TRAIL receptors, IAPs, and p53 using antibodies conjugated to different Q-Dots. Ongoing studies include prognostic marker, stem cell marker, and cell proliferation/death response marker analysis in human tumor xenografts of HCT116, p53-null HCT116, DLD1, SW620, and SW480. Initial profiling of tumor cell lines revealed that mutant p53 and KRAS-expressing SW620 derived from a patient with mCRC has CD26 and CD133 expression including a sub-population of tumor cells that co-express these two stem cell markers. HCT116 showed positive EGFR, CD26, but little or no CD133 expression. We are evaluating correlations between the primary tumors in mice as compared to the CTCs in mice and similar experiments are part of the clinical protocol. The studies should unravel the complexity of CTC heterogeneity, and define informative subsets of markers that can be routinely included in studies to assess prognosis and response to therapy. The ease with which CTCs can be isolated makes these studies of comparisons with primary tumors critical in order to establish and validate new methods for assessing tumor behavior and response to therapy in the clinic through this CTC “liquid biopsy” technique. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5248. doi:10.1158/1538-7445.AM2011-5248