Stem Cells and Cancer

We have noted that adult stem cell populations exhibit functional decline with age. Ageing is also associated with a dramatic increase in the incidence of cancer, and several recent studies support a stem cell origin for cancer (Campisi 2003, Campisi 2005, Kaplan et al. 2006, Li and Neaves 2006, Rizo et al. 2006, Li et al. 2007). Together, these findings offer strong support to the stem cell theory of ageing by connecting functional decline in the stem cell population to malignancy resulting in limited organismal longevity. Interestingly, from the cell surface, stem cells from a variety of tissues resemble their malignant counterparts. Hematopoietic, mammary, neural, lung, skin, and prostate stem cells can be identified by some of the same cell surface markers used to identify cancer stem cells in these tissues (Li et al. 2007). In addition to cell intrinsic similarities between normal stem cell and cancer cells, an enormous body of literature describes intricate relationships between transformed cells and their supportive niches in the primary tumor and sites of metastasis. Similarities between stem cell-microenvironment and cancer cell-microenvironment interactions have been extensively reviewed by Rizo et al. (2006), Kaplan et al. (2006), Li et al. (2007) and others. Although it is beyond the scope of this publication to adequately summarize all of the relationships that are common to physiological and transformed stem cells and their microenvironment, several key points are briefly summarized below.

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