P4-07-20: Apoptosis in Circulating Tumor Cells (CTCs) of Early and Metastatic Breast Cancer Patients.

Abstract

Abstract Background: Metastasis has been associated with the presence of circulating (CTCs) and disseminated (DTCs) tumor cells in peripheral blood and bone marrow of breast cancer patients, respectively. Recent studies have confirmed that the detection of CTCs and DTCs represents a strong and independent prognostic factor for decreased disease-free and overall survival. However, it is not clear so far whether all CTCs are capable to generate metastasis or some of them are destined to die. The aim of the present study was to analyze the presence of apoptotic CTCs in patients with early and metastatic breast cancer. Patients and methods: Double staining immunofluorescent (IF) expreriments were performed in peripheral blood mononuclear cells (PBMC) cytospins of patients with early (n=23) and metastatic breast cancer (n=29), prior to the initiation of adjuvant and first-line chemotherapy, respectively. Pancytokeratin A45-B/B3 antibody (as a marker of CK-positive cells) was coupled with either M30 (marker of apoptotic cells) or Ki67 (marker of proliferating cells) antibodies. Apoptotic CTCs were also evaluated using a polycaspase detection kit. Results: Significantly lower proportions of apoptotic CTCs were detected in metastatic compared to early breast cancer patients using the polycaspase kit (3% vs 49%, p=0.0001). These results were confirmed with M30 staining (32% vs 67%, in metastatic and early disease, respectively, p=0.023). The median percentage of apoptotic CTCs per patient was also lower in advanced compared to early disease patients (0% vs 100% with the polycaspase kit and 15% vs 70% with M30 staining). Ki67 positive CTCs were identified in 56% of early and metastatic patients, while the ratio of Ki67-positive/Total CTCs was 15% and 36% respectively. Conclusions: Apoptotic CTCs are more commonly observed in early compared to metastatic breast cancer, whereas, Ki-67 positive CTCs are more frequently encountered in metastatic disease. The differential incidence of apoptotic and proliferative CTCs in early and metastatic disease is probably related to disease progression. The evaluation of these markers in CTCs from patients with breast cancer may provide useful prognostic information and could be used to monitor the effectiveness of therapy. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P4-07-20.