Features of ALDH+cell population in monolayer and mammosphere culture. (A) Flow cytometry revealed 7.6% of the xenografted tumor cells in BC-P007MT3 (passage 3) were positive for ALDEFLUOR assay. (B) The ALDEFLUOR-positive cells were incubated in a culture dish, and formed colonies spontaneously (200×). (C) BC-P007 ALDH+ cell are capable of generating mammospheres in culture (200×). (D) As few as 50 ALDH+ harvested from mammospheres (S) or monolayer (M) were sufficient for tumor engraftment. ALDH, Aldehyde dehydrogenase 1.