A powerful set of cells in bladder tumours, identified by researchers at John Hopkins, appear to be primarily responsible for the cancer's growth and spread.
The researchers have long suspected that a subset of cells in cancerous tumours act much like developmentally primitive cells known as stem cells, which spur organ development early in life and remain present in nearly all the body's organs to repair or replace injured and aging tissues.
These cancer cells and stem cells share a variety of characteristics including an unlimited lifespan and a propensity to migrate through tissues.
If researchers find a way to identify and specifically target cancer cells with these properties, they could wipe out the population that sustains tumours and makes them grow.
The researchers reasoned that if these stem-like cancer cells behave like healthy stem cells, they might be physically located in the same compartments in tissue where stem cells normally reside.
During the study, using a surface protein marker previously identified for healthy bladder stem cells, the Hopkins team searched for cells with the same marker in sections from 55 human bladder tumours.
They found that cancer cells displaying the marker were localized in an area at the intersection of two layers of cells known as epithelium and stroma, the place where bladder stem cells are typically located.
Using cancer cell lines grown from other bladder cancer patients, the researchers separated cells displaying the stem cell marker from those without it and injected these two different sets of mice.
The mice injected with the cancer cells displaying the marker always grew tumours, but those injected with the other cancer cells rarely did, suggesting that the stem-like cancer cells have an ability to create new tissue much like healthy stem cells do.
The study also showed that genes linked to cell proliferation and metastasis were most active in stem-like cells than in the other cancer cells.
The findings appear in journal Stem Cells.