Circulating CD68 positive (+) leukocytes in blood samples from patients (pts) with breast cancer (BC).

Abstract

172 Background: Several different CD45 + leukocyte populations are present in primary breast tumors and stroma (Coussens et al, 2011). These include CD4+/CD8+ T cells and myeloid derived cells such tumor associated macrophages/monocytes (TAMs). TAMs are under investigation as prognostic and predictive markers during chemotherapy (CX). The detection of TAMs has been restricted thus far to tumor tissue. We hypothesized that we can detect changes in CD45+ leukocyte populations in blood samples obtained before and during CX from pts with early and advanced BC. Methods: Venous blood samples from BC patients were collected, and were either directly analyzed or further processed using previously described immunomagnetic negative depletion. Multistep, sequential labeling was performed to first label and fix cell surface markers followed by permeablization for cytokeratins, before and after negative depletion, followed by multiparameter flow cytometry analysis for the following basic markers: CD45, cytokeratins, and EpCAM, and for a subset of patients additional markers including: CD13, CD14, CD68, and CD133. Results: Forty blood samples were analyzed and study is ongoing. Different CD45+ subpopulations were observed in peripheral blood including: a) CD45+, CK+, CD68 negative (-), b) CD45+, CK+, CD68+, c) CD45+, CK+, CD68+, CD14+, and CD16+. In addition, there was a trend in increasing CD 68+ leukocytes after 1 cycle of CX in pts with poor response to therapy or progression of disease. No abnormal cell subpopulations were present blood samples from healthy volunteers. Conclusions: This is the first study to report various peripheral blood leukocyte populations in BC that are similar to those observed in primary breast tumor stroma. The precise origin of these CD45 + cells is under investigation, including additional phenotypic characterization for TAMs. Results will be correlated to patient stage, tumor subtype and response to therapy.