A recent series of papers [1-3] have prompted me to write about
the cancer stem cell (CSC) hypothesis, since during the last
years there has been a lot of controversy regarding the
existence, function and clinical implications of cancer stem
cells. This confusion stems (no pun intended) from the lack of
clarity in the field nowadays, arising mainly from
misconceptions regarding the origin and function of these cells.
On top of all of this is the confusion derived from media-hype
and some not-so knowledgeable scientific journalists. The
classical view of tumor biology is that transformed cells, which
carry mutations that confer them selective advantages under
certain conditions, divide continuously forming a homogeneous
tumor. This concept entailed the idea that every clone of the
original tumor proliferates indefinitely as an autonomous entity
within the whole malignant cell population, and if removed from
the tumor and placed somewhere else it could generate a new
tumor. The cancer stem cell hypothesis chall