Disseminated tumor cells in primary breast cancer: Evaluation of the percentage of breast cancer stem cells in bone marrow aspirates of patients receiving neoadjuvant chemotherapy

505 Background: Disseminated tumor cells (DTC) in the bone marrow (BM) are related to poor prognosis of primary breast cancer (PBC). Cancer-initiating stem cells (CSC) have been detected in BM of PBC patients. Downregulation of the Notch pathway leads to murine mammary stem cell expansion and its expression is an early event in breast cancer. We enumerated CSC in BM mononuclear cells (BMC) and assessed the expression of Notch-1, ER, and HER-2 to study the differences between untreated patients and those treated with neoadjuvant chemotherapy. Methods: BM was collected from 90 PBC patients at time of surgery to assess DTC (CD326+CD45-) and CSC (CD326+CD45-CD44+CD24-) by FACS analysis. BM samples were also interrogated for the presence of CSC with ALDH activity using the Aldefluor® detection kit. RNA extracted from 61 BMC was analyzed for Notch-1, ER, and HER-2 transcripts by RT-PCR; the level of each transcript was normalized to that of the housekeeping gene, GAPDH. Results: The median age of patients is 51...