UCLA researchers develop new PET scanning probe that will allowing monitoring of the imm...( Researchers at UCLA's Jonsson Compre...)

Researchers at UCLA's Jonsson Comprehensive Cancer Center have modified a common chemotherapy drug to create a new probe for Positron Emission Tomography (PET), an advance that will allow them to model and measure the immune system in action and monitor response to new therapies.

The discovery, published June 8, 2008 in the early online edition of the journal Nature Medicine, enables scientists to monitor the immune system at the whole body level in 3D as it tries to fight some cancers or when it goes awry as it does in autoimmune diseases.

Researchers created the small molecule, called FAC, by slightly altering the molecular structure of one of the most commonly used chemotherapy drugs, gemcitabine. They then added a radiolabel so the cells that take in the probe can be seen during PET scanning.

The probe is based on a fundamental cell biochemical pathway called the DNA Salvage Pathway, which acts as a sort of recycling mechanism that helps with DNA replication and repair. All cells use this biochemical pathway to different degrees. But in lymphocytes and macrophages, the cells of the immune system that initiate immune response, the pathway is activated at very high levels. Because of that, the probe accumulates at high levels in those cells, said Dr. Owen Witte, a researcher at UCLA's Jonsson Cancer Center, a Howard Hughes Medical Institute investigator and senior author of the study.

"This is not a cure or a new treatment, but it will help us to more effectively model and measure the immune system," said Witte, who also serves as director of the Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research at UCLA. "Monitoring immune function using molecular imaging could significantly impact the diagnosis and treatment evaluation of immunological disorders, as well as evaluating whether certain therapies are effective."

Because the probe is labeled with positron emitting particles, cells that
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