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If the same approach works in humans, it could offer a way to catch prostate cancer as it begins to spread, they said.
Ultimately, the hope is to use the approach to kill cancer cells as part of a highly targeted, image-guided therapy.
"If we can catch the cancer before it invades other organs, we have a better chance to change the outcomes for these patients," Lily Wu of the University of California, Los Angeles, whose study appears in the journal Nature Medicine, said in a statement.
How the research was done
The finding offers an example of a much-anticipated new use of imageing technology known as molecular imageing, in which advanced diagnostic equipment can be used to target and treat cancers on the cellular level.
Conventional scans known as computed tomography or CT scans have a hard time spotting the earliest stages of prostate cancer as it spreads, or metastasizes, to hard-to-reach lymph nodes in the pelvis.
To help get a better look, Wu's team tinkered with the common cold virus so that it would only target prostate cancer cells.
Once inside the cancer cell, genes in the virus trick the cancer into making a protein that can be seen using positron emission tomography, or PET scans. The protein serves as a sort of a flare signal identifying the location of the cancer.
"The virus happens to be lymphotropic, which means it favors the lymph nodes. We were able to exploit its natural capability for this particular function," Wu said in a telephone interview.
Virus could target and tag prostate cancer cells
Using genetic engineering, Wu said her team deleted all of the parts of the cold virus that make people sick. Next, they spliced in genes that make proteins that can be seen on PET scans, and they added in other genes that target prostate cancer cells.
"It's a prostate cancer-specific control switch," Wu said.
The result was a virus that specially looked for prostate cancer cells in the lymph nodes, which is typically the first stop cancer makes before it spreads to other organs.
When Wu and her team injected the engineered virus into tumors in mice with prostate cancer, PET scans picked up signals only from lymph nodes with cancer cells in them, suggesting the virus was able to target and tag prostate cancer cells.
Wu and her colleagues are now working to develop a toxic agent they can add in that would find and kill the cancer cells at the same time, watching it all on a PET scanner.
She said the team plans to start testing the technique in dogs with prostate cancer. Her team is working to perfect the technique so that it can be tested in humans within the next two years, she said.
Prostate cancer occurs usually in older men. With an estimated 254,000 deaths annually, prostate cancer is the sixth leading cause of cancer death in men worldwide. – (Reuters Health)
July 2008
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