Tumor-Tagging Chemical

It may be the too-good-to-be-true cancer news you’ve been waiting for: a new chemical agent can pinpoint and treat tumors in the body, and is effective at finding cancer cells that are resistant to treatment.

Researchers from the University of Wisconsin's (UW) Carbone Cancer Center published their findings in Science Translational Medicine. In the article, they discuss animal studies and human clinical trials that show how the alkylphosphocholine (APC) molecule can deliver a radioactive or fluorescent imaging tag to cancer cells, or deliver a radioactive medicine that binds to and kills the cells.

Cancer cells lack the enzymes needed to break down phospholipid ethers, a part of cell membranes that is easily broken down by normal cells. APC exploits this shortcoming. APC is injected and travels throughout the body—even across the blood-brain barrier—and sticks to cancer cells' membranes. These cells take in the APC along with the imaging or treatment medication and store it for days or weeks, resulting in direct cancer cell imaging or treatment. The researchers say that the APC treatment was able to tag cells from 55 out of 57 different cancers they studied.

Dr. John S. Kuo, Ph.D., an associate professor of neurological surgery and director of the Comprehensive Brain Tumor Program at the UW Hospital and Clinics, said that a therapeutic radio label like the Iodine-131 isotope could also be added to APC to directly treat cancer cells in the body, including cancer cells that have spread to or grown in the brain. He said that the therapy shows “promising results” for treating renal, breast, ovarian, colorectal, lung, melanoma, and brain cancers in mice. The team has preliminary data showing that it works for other cancers too, with the exception of liver cancer.

“I was a skeptic; it's almost too good to be true,” Kuo said in a press release. “It is a very broad cancer-targeting agent in terms of the many different cancers that tested positive.”

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Kuo worked with Jamey P. Weichert, Ph.D., an associate professor of radiology at UW and chief scientific officer of Cellectar Biosciences, Inc., a local company developing the APC platform for cancer imaging and therapy.

“The APC analogs appear to be very broadly targeted against cancer,” Kuo said. “The APC analogs even sometimes revealed other sites of cancer in patients that were small, asymptomatic, and previously undetected by physicians.”

Kuo focuses on treating brain tumors, and leads a group conducting trials on glioma, an incurable type of brain cancer that, even when treated, leaves behind cancer stem cells that can seed and later regrow the cancer. The APC method detected these cancer stem cells and may also be able to target them for treatment.

APC imaging might also help avoid false-positive results that can sometimes occur with current imaging techniques.

“During clinical follow-up in the course of cancer treatments, this is potentially important to help patients avoid second look surgeries or discontinuation of effective cancer therapies because of ‘false-positive’ imaging results from current methods of cancer detection,” Kuo said.

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Because APC directly labels cancer cells, it is likely superior to current MRI or CT scans or FDG-PET imaging at revealing cancer cells, as well as avoiding false-positive signals from the effects of treatment, surgical scars, or infection and inflammation, Kuo said.

Kuo said there are already ongoing human clinical trials of APC agents at the UW Medical Center and at other National Cancer Institute(NCI)-designated centers around the country. These have verified the safety of APC agents, but more work is needed.

“We need to prove it [works] for every single cancer type,” he said.

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