Introducing the concept of breast cancer stem cells

Abstract

Breast tumours are well known to be composed of phenotypically diverse groups of cells. Which of these cell types contribute to tumour development, however, is not well understood. Two hypotheses exist: either all the cell populations have the capacity to become tumourigenic through mutation accumulation, or this ability is confined to a select 'elite' group [1]. In acute myelogenous leukaemia it has been shown that a distinct subset of cells has increased ability to initiate tumourigenesis and may be identified with specific cell surface markers [2,3]. This phenomenon has not been shown in solid tumours until the recent publication by Al-Hajj and colleagues where they describe a method for differentiating 'tumour-initiating' or 'tumourigenic' breast tumour cells from non-tumourigenic cells [4].