Abstract 3285: Phenotypic characterization of circulating tumor cells (CTCs) in triple negative breast cancer patients

Abstract

Abstract Background: Molecular classification of breast cancer revealed that there are five different subtypes related to clinical outcome:. luminal A, luminal B, normal-like, ERBB2-positive and basal-like. Triple negative patients (ER-negative, PR-negative, HER2-negative) belong to the basal-like subtype. Their tumors commonly express EGFR and are associated with poor prognosis. 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, for the first time, the phenotypic characterization of CTCs in triple negative breast cancer patients. Methods: We evaluated peripheral blood mononuclear cells (PBMC) cytospins from 40 triple negative patients and found CTCs in thirty one of them (15 early and 16 metastatic). The expression of Cytokeratins (CK), Estrogens Receptor (ER), Progesterone Receptor (PR), Epidermal Growth Factor Receptor (EGFR) and Human Epidermal Growth Factor Receptor (HER2) in CTCs was assessed using double immunofluorescent staining and confocal laser scanning microscopy and the Ariol system. PBMCs were stained with a monoclonal A45-B/B3 pancytokeratin antibody in combination with ER, PR, EGFR or HER2 antibodies, respectively. Results: Our results demonstrated that ER, PR, EGFR and HER2 were expressed in 58%, 45%, 55% and 58% of the examined CK-positive patients. The respective proportions for early versus (vs) metastatic patients were 67% vs 50% for ER, 53% vs 38% for PR, 60% vs 44% for EGFR and 60% vs 56% for HER2. In addition ER, PR, EGFR and HER2 were expressed in 5.6%, 79.7%, 80.7% and 13.4%, respectively, of the total examined CTCs. Triple staining experiments with the Ariol system revealed no co-expression of CK/EGFR/ER in CTCs; however, there was only one patient with CTCs co-expressing CK/HER2/ER. Conclusions: ER is expressed but in a minority of CTCs in triple negative breast cancer patients though the majority of CTCs revealed expression of PR and EGFR. However the clinical significance of these findings remain unknown and need further evaluation. Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3285.