The AC133 antigen is selectively expressed on subset of CD 34+ cells isolated from leukapheresis products from high risk breast cancer patients receiving chemotherapy plus G-CSF. MiniMACS AC133+ isolated cells contained a mean of 85% (80-90) AC133+ cells. Enriched AC133+ cells coexpressed 80% CD34+, 6.6% CD33+ and 2% CD15+. Separated AC133+ cells contained 600 GFU-GM/10(4) cells and 70 BFU-E/10(4) cells. Flow-cytometric analysis indicated that AC133+ cells were isolated from cells population with low granularity (SS), while CD33+ a CD15+ cells had a high granularity. After a seven-day ex vivo expansion in the presence of SCF + IL-3 + IL11, the expansion of cells increased 19.4 times. The mean percentage of blasts decreased from 100% at the start of culture to 81% on day 3 and 30% on day 7. Promyelocytes were slow to appear with 10% present on day 3, but thereafter increased to 33% on day 7. The appearance of myelocytes and metamyelocytes lagged 3 days behind promyelocytes and continued to increase during culture to become the predominant (30%) cell type on day 7. Very few neutrophils (2%) were observed in any of the cultures on day 7. Monocytes or macrophages were not detected on day 7. By day 7 megakaryocytes were present at low levels (10%). The mean value of CFU-GM in the culture after day 7 of ex vivo expansion in the presence of SCF+IL-3+IL-11 had increased 45-fold, BFU-E 5-fold. After 7 days of expansion with IL-3+SCF+IL-11 cells expressed a mean of 12% CD34+, 8% AC133+, 59% CD33+ and 30% CD15+. The aim of this experiment was to determine whether ex vivo culture of peripheral blood AC133+ cells could generate sufficient numbers of progenitors to potentially abrogate cytopenia after transplantation and passive purging of tumor cells.

Department of Oncology and Radiotherapy Charles University Hospital Czech Republic