Abstract 5107: Phenotypic characterization of circulating tumor cells (CTCs) in triple negative breast cancer patients.

Abstract

Abstract Triple negative (ER-negative, PR-negative, HER2-negative) considered as poor prognosis breast cancer patients without many therapeutic options. Circulating Tumor Cells (CTCs) have been proposed as a “real time liquid biopsy” in breast cancer patients. CTCs are associated with disease relapse and could serve as a target for molecular cancer therapies. The aim of the present study was the phenotypic characterization of CTCs in triple negative patients to explore new therapeutic strategies for these patients. We evaluated peripheral blood mononuclear cells (PBMC) cytospins from 29 triple negative patients, before the initiation of adjuvant (19 early) and front-line (10 metastatic) treatment. The expression of Cytokeratins (CK) (marker for CTCs), Estrogen Receptor (ER), Progesterone Receptor (PR), EGFR and HER2 in CTCs was assessed using double immunofluorescent experiments. Our results revealed that median expression per patient for ER, PR, EGFR and HER2 was 16.7%, 0%, 42.9% and 91.4%. The respective numbers for early versus (vs) metastatic patients were 29.7% vs 0% for ER, 27.1% vs 0% for PR, 70.8% vs 52.3% for EGFR and 50% vs 48.7% for HER2. In addition ER, PR, EGFR and HER2 were expressed in 33.1%, 28%, 67.7% and 45.1%, respectively, of the total examined CTCs. Triple staining experiments with the Ariol system could not revealed any no co-expression of CK/EGFR/ER in CTCs; however, there was only one patient with CTCs co-expressing CK/HER2/ER. Consequently in order to identify whether chemotherapy could induce phenotypic changes of CTCs, 18 patients were analyzed after the completion of adjuvant treatment. ER, PR, EGFR and HER2 median expression per patients was identified in 0.2%, 15.2%, 66.7%, and 50% suggesting that adjuvant chemotherapy does not significantly influence the phenotype of CTCs in triple negative patients.The majority of CTCs in triple negative patients revealed expression of HER2 and EGFR implying that these receptors could be a potential target for the limitation of metastasis in these patients. Citation Format: Galatea Kallergi, Haris Markomanolaki, Dimitrios Mavroudis, Vassilis Georgoulias, Sofia Agelaki. Phenotypic characterization of circulating tumor cells (CTCs) in triple negative breast cancer patients. [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 5107. doi:10.1158/1538-7445.AM2013-5107