Fluorescent Compounds Make Tumors Glow

A series of novel imaging agents could light up tumors as they begin to form – before they turn deadly – and signal their transition to aggressive cancers.

The compounds – fluorescent inhibitors of the enzyme cyclooxygenase-2 (COX-2) – could have broad applications for detecting tumors earlier, monitoring a tumor’s transition from pre-malignancy to more aggressive growth, and defining tumor margins during surgical removal.

“We’re very excited about these new agents and are moving forward to develop them for human clinical trials,” said Lawrence Marnett, Ph.D., the leader of the Vanderbilt University team that developed the compounds, which are described in the May 1 issue of Cancer Research.

COX-2 is an attractive target for molecular imaging. It’s not found in most normal tissues, and then it is “turned on” in inflammatory lesions and tumors, Marnett explained.

“COX-2 is expressed at the earliest stages of pre-malignancy – in pre-malignant lesions, but not in surrounding normal tissue – and as a tumor grows and becomes increasingly malignant, COX-2 levels go up,” Marnett said.

Compounds that bind selectively to COX-2 – and carry a fluorescent marker – should act as “beacons” for tumor cells and for inflammation.

Marnett and his colleagues previously demonstrated that fluorescent COX-2 inhibitors – which they have now dubbed “fluorocoxibs” – were useful probes for protein binding, but their early molecules were not appropriate for cellular or in vivo imaging.

“It was a real challenge to make a compound that is COX-2 selective (doesn’t bind to the related COX-1 enzyme), has desirable fluorescence properties, and gets to the tissue in vivo,” Marnett said.

To develop such compounds, Jashim Uddin, Ph.D., research assistant professor of Biochemistry, started with the “core” chemical structure of the anti-inflammatory medicines indomethacin and celecoxib. He then tethered various fluorescent parts to the core structure, ultimately synthesizing more than 200 compounds. The group tested each compound for its interaction with purified COX-2 and COX-1 proteins and then assessed promising compounds for COX-2 selectivity and fluorescence in cultured cells and in animals. Two compounds made the cut. Read more

FDA Approves A Cellular Immunotherapy For Men With Advanced Prostate Cancer

The U.S. Food and Drug Administration approved Provenge (sipuleucel-T), a new therapy for certain men with advanced prostate cancer that uses their own immune system to fight the disease.

Provenge is indicated for the treatment of asymptomatic or minimally symptomatic prostate cancer that has spread to other parts of the body and is resistant to standard hormone treatment.

Prostate cancer is the second most common type of cancer among men in the United States, behind skin cancer, and usually occurs in older men. In 2009, an estimated 192,000 new cases of prostate cancer were diagnosed and about 27,000 men died from the disease, according to the National Cancer Institute.

“The availability of Provenge provides a new treatment option for men with advanced prostate cancer, who currently have limited effective therapies available,” said Karen Midthun, M.D., acting director of the FDA’s Center for Biologics Evaluation and Research.

Provenge is an autologous cellular immunotherapy, designed to stimulate a patient’s own immune system to respond against the cancer. Each dose of Provenge is manufactured by obtaining a patient’s immune cells from the blood, using a machine in a process known as leukapheresis. To enhance their response against the cancer, the immune cells are then exposed to a protein that is found in most prostate cancers, linked to an immune stimulating substance. After this process, the patient’s own cells are returned to the patient to treat the prostate cancer. Provenge is administered intravenously in a three-dose schedule given at about two-week intervals. Read more

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