Stem Cell Alter Egos

Researchers show that cancer stem cells can exist in two distinct and interconvertible states.

Apr 1, 2014
Abby Olena

TWO-FACED: The invasive edge of a tumor (left) harbors mesenchymal-like breast cancer stem cells (green), while the interior of the tumor (right) contains epithelial-like cancer stem cells (pink).REPRINTED FROM S. LIU ET AL., STEM CELL REPORTS, 2:78-91, 2014

EDITOR'S CHOICE IN CELL BIOLOGY

The paper
S. Liu et al., “Breast cancer stem cells transition between epithelial and mesenchymal states reflective of their normal counterparts,” Stem Cell Reports, 2:78-91, 2014.

The states
Cancer metastasis is thought to rely on tumor cells losing their polarity and their connections with neighbors, enabling them to migrate and invade other tissues—an epithelial-to-mesenchymal transition. The reverse process—the mesenchymal-to-epithelial transition—then allows cells to set up shop in a new tissue. Cancer stem cells can express genes associated with both pathways, but there have been conflicting findings about the relationship between stemness and these transitions.

The finding
Cancer biologist Max Wicha of the University of Michigan and colleagues showed that breast cancer stem cells (BCSCs) in the same tumor can exist in both states. They found invasive, mesenchymal-like BCSCs at the edges of tumors, while proliferative, epithelial-like BCSCs were localized toward tumors’ interiors. The researchers also demonstrated that the two states are interconvertible, and they suggested that this plasticity might be required for metastasis.

The resolution
“Heterogeneity of breast cancer stem cells . . . has been an area of intense investigation and, frankly, confusion for a lot of people,” says Charlotte Kuperwasser of Tufts University School of Medicine who was not involved in the work. By showing that BCSCs can alter their identity, the authors “have done a good job of unifying the field and observations that others have made,” she says.

The applications
Although breast cancer subtypes are treated differently in the clinic, “the stem cells have much more in common than we thought,” Wicha says. “As we develop therapies that can target cancer stem cells, they may be useful in [multiple] forms of breast cancer.”