Anti-Cancer 'Smart Bomb' Homes in on Deadly Tumors

Using a line of stem cells developed at the University of British Columbia Hospital in Vancouver that can be easily reproduced in the lab, Aboody and her colleagues engineered the cells to carry an enzyme that could enrich the standard chemotherapy drug, CPT-11.

"CPT-11 is the drug that's used to treat kids today," Aboody said. "It goes throughout the body and only a very small percent of it reaches the tumors."

But the researchers found that when CPT-11 encounters an enzyme secreted by the stem cells, it turns into SN-38.

"That's a thousand times more effective than CPT-11," Aboody said.

But it kills everything it encounters.

So the researchers treated mice that had been inflicted with metastasized tumors three different ways. One group of mice was given no treatment at all. They all died by day 75.

The second group received only CPT-11.

"At first they responded, but then they stopped," Aboody said. "They survived longer, but by day 175 only about 50 percent were alive."

The rest of the mice were given both the CPT-11 and the stem cells engineered to convert it to SN-38 at the site of the tumor.

They were all alive at day 175.

The scientists took another look at the animals a year into the study. Only 30 percent of those given just CPT-11 were still alive. But 90 percent of those treated with stem cells and CPT-11 were still alive.

"So that's a year, on a two-and-a-half-year lifespan," Aboody noted.

However, there is some concern among researchers over the end result of introducing foreign stem cells into any human. These remarkable cells can morph into any type of cell tissue, and what would happen if the cells introduced in the fight against cancer turned eventually into something quite harmful?

That concern alone could hold up human trials, but preliminary findings from Aboody and her colleagues indicate that the cells don't hang around after knocking out the cancer.

"When we looked at the organs of the mice that survived a whole year we didn't see any sign of tumors or stem cells," she said.

She theorized that the stem cells may fall victim to their own mission.

"They are giving off this enzyme and the drug is surrounding it, and it's killing all the tumor cells, and it's a very toxic environment," she said. "So it's likely the stem cells are also eliminated."

That would be convenient, to say the least. After they've completed their mission, they're destroyed by the toxicity they helped deliver.

A lot more research will have to be finished before that's known for sure, but Aboody has already set her sights on another target.

She wants to show that the same system can be used to target such common cancers as lung, prostate and breast.

The latter is of special concern to her -- she lost her sister--in-law to breast cancer five years ago, and her research is dedicated to her memory.

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