Are Cancer Stem Cells Real? After Four Decades, Debate Still Simmers

Extract

Scientists first hypothesized the existence of cancer stem cells in the early 1970s, when they discovered two distinct subpopulations of leukemia cells, one that could proliferate much more rapidly than the other. The morphological differences between the groups suggested that it would be possible to separate them and study the quickly proliferating cells, which, some believed, were giving rise to the more slowly dividing subset.

Thus was born the cancer stem cell model of carcinogenesis, which holds that only a specific subset of the cells within a tumor is tumorigenic, giving rise to other tumor cells or to distant metastases. Some believe that these cells are also highly resistant to chemotherapy or radiation treatment and may be the reason that cancers recur after nearly disappearing.

But not everyone believes in the stem cell model. Instead, some say that cancer is better explained by the stochastic (or clonal evolution) model, which holds that most or all cancer cells have inherent tumorigenic potential. According to this model, the heterogeneity among tumor cells exists because of variations in the levels of transcription factors within cells or in their ability to promote angiogenesis and create a favorable microenvironment for themselves.