Stanford researchers identify human bladder cancer stem cell

Researchers at the Stanford University School of Medicine, Stanford, CA have identified the first human bladder cancer stem cell and have explained its role in evading the body’s natural defenses.

"This is first time we’ve found this 'don’t eat me signal' in a stem cell of a solid cancer," said senior study author Irving Weissman, MD. "We’re now moving as fast as we can to look at other tumors to see if this is a universal strategy of all or most cancer stem cells."

Detecting and tracking the stem cells may be one way to monitor tumor status, researchers say, and targeting the cells to be destroyed may be a means to remove the cancer.

To find a subpopulation of human bladder cancer cells with stem cell qualities, the team used breast cancer stem cell markers. When transplanted into mice that had weakened immune systems, the cells formed tumors. Researchers observed which genes were more highly expressed in the cells than in other bladder cancer cells from the same tumor.

Findings showed most, but not all, noninvasive bladder cancers indicated lower levels of the genes than invasive cancers did. Further, the anomalous noninvasive cancers with higher levels of gene expression were more aggressive: 80% recurred within 25 months of diagnosis; only 20% of non-expressive tumors did.

One cell was discovered that encodes a cell-surface molecule called CD47. CD47 prevents leukemia cells from being consumed by macrophages by binding to a molecule on the macrophage surface. Preventing contact with an antibody specific to CD47 enables the macrophages to consume the leukemia cells.

The study is published in the Aug. 3 Proceedings of the National Academy of Sciences.