Detection of stromal cells in peripheral blood progenitor cell collections from breast cancer patients

Transplantation of growth factor-mobilized peripheral blood progenitor cells (PBPC) is widely used in the treatment of several neoplastic diseases. While in PBPC harvests the presence of several accessory immune and tumor cells has been documented, that of stromal cells has not been reported. In the present study, we investigated for the presence of stromal cells in growth factor-mobilized PBPC harvests from breast cancer patients. Low-density cells from PBCP harvests in culture gave rise to an adherent layer containing fibroblast-like and large flat round cells. These cells express positive immunofluorescence staining for collagen I, collagen III, fibronectin, VCAM-1 (CD106), ICAM-1 (CD54) and mesenchymal antigens recognized by monoclonal antibodies, SH2 and SH3. PBPC-derived stromal cells do not express antigens CD34, CD45 and CD14. Stromal cells were detected in the PBPC harvests of 11/14 patients (median 0.63%; range 0.02-2.32) and their concentration correlates with the number of CD34+ cells in PBPC.