A new imaging agent – radio-labelled hedgehog - detects cancer stem cells, potentially allowing for imaging of "stem cell-like" cancer cells by positron emission tomography (PET) in patients with breast cancer, according to results of a pilot study, presented at the American Association for Cancer Research 101st Annual Meeting 2010.

Cancer stem cells are resistant to chemotherapy and radiotherapy and can lead to tumour regrowth after treatment. Tumours that are rich in stem cell-like cancer cells are more likely to recur after treatment and to metastasize. Detecting these cells early means timely initiation of aggressive treatments to minimize relapse and improve therapeutic outcome. It may also be useful in evaluating new stem-cell targeted cancer therapies.

Jennifer Sims-Mourtada, Ph.D., Director of molecular research and development at RadioMedix, Inc., Houston, Texas, and colleagues tested the ability to detect breast cancer stem cell-like populations using a protein, sonic hedgehog that was radiolabeled with the positron emitting isotope Gallium-68.

Increased activation of the hedgehog pathway is observed in cancer stem cells and aggressive tumours.

Binding of the radio-labelled hedgehog to the Patched-1 hedgehog receptor on the surface of breast cancer cells occurred, suggesting potential for molecular imaging of breast cancer by PET. A significant increase in binding was observed in cultures enriched for breast cancer stem-like cells.

"Our study is the first to show that radiolabeled hedgehog is capable of differentiating stem-like cancer cells compared to the entire tumour population," she said. "Additionally, this agent can potentially identify aggressive tumours."

These results are being validated in further laboratory work and microPET imaging studies are underway to assess the value of this agent for imaging tumours that are rich in cancer stem cell populations, according to Sims-Mourtada.

Source: The American Association for Cancer Research