A Mouse with the Same Cancer as You

At a laboratory in Baltimore, hairless mice kept in racks of plastic crates are labelled with yellow cards, each identifying a person fighting cancer. These mice are cancer “avatars”—the lumpy tumors visible under their skin come from actual patients.

The animals serve as personalized, living test tubes. Each mouse will eventually be treated with a different drug and its tumors measured. Results showing which medicine worked best will be sent back to a doctor trying to treat a difficult cancer case.

The technology is a twist on personalized medicine that’s being developed by Champions Oncology. The company, based in New Jersey and Maryland, has started offering mouse avatars directly to patients, at a cost of $10,000 to $12,000. Insurance companies don’t yet pay for the technology, which remains experimental.

In the service Champions is selling, doctors first remove a piece of a patient’s tumor during a surgery or biopsy. Then they ship it to the company, where it gets grafted under the skin of an immune-deficient mouse. Because the rodents have impaired defenses, the human tumor is able to grow. Parts of it can be removed and implanted in additional mice.

The data from the avatars is potentially life-saving, since the choice of what drug to give a cancer patient is often made by guesswork or trial and error. “Generally, the drugs we give to patients are more likely to not work than to work,” says Justin Stebbing, an oncologist at the Imperial College London, who has been involved in medical studies of Champions’s technology. The results from the personalized mice, he says, “give patients an additional layer of confidence.”

Cancer avatars are part of a wider effort to carry out experiments on people’s tumors outside their bodies. Some researchers have created fruit flies that share the same gene mutations patients have. Another technology, still in development, looks to capture floating tumor cells from a person’s bloodstream, then grow and test them in culture dishes (see “A Laboratory for Rare Cells Sheds Light on Cancer”). Still further out, scientists have plans to grow mini-organs, complete with an immune system that matches the patient’s (see “Building an Organ on a Chip”).

Don Ingber, director of the Wyss Institute for Biologically Inspired Engineering at Harvard University, says these outside-the-body approaches face some similar challenges. For one, cancer cells vary so much that it’s not certain the tumor in the mouse is the same as the one in the person. What’s more, the immune system is closely involved in the body’s response to cancer, but these mice lack one. “I think the real issue is that it’s still a mouse,” he says. 

Champions, founded in 2007, has successfully grown tumors from more than 350 patients, says company president Ronnie Morris. In June, the company said it would collaborate with the Icahn School of Medicine at Mount Sinai, in New York, to create mouse avatars for an additional 100 breast cancer patients. “On the whole, it seems to yield very convincing data that’s predictive, so it tells you what treatment is going to work ahead of giving these expensive and toxic drugs,” says Stebbing, who has tried the technology with patients suffering from rare or unusual cancers.

Not every graft works. In about 30 percent of cases, Champions hasn’t been able to grow a patient’s tumor in mice. But the biggest limitation to cancer avatars is that tumors grow at about the same speed in a mouse as in a person. That means the avatars won’t be helpful for patients who need to be treated quickly, as is often the case. Morris says it takes four to six months to grow the tumors, treat the mice, and send doctors a report.

In a study Stebbing published in April in the journal Cancer, for instance, Champions created avatars for 22 patients with advanced sarcoma. But nine of the patients died before the results were ready. “Within a couple of months after their surgery or biopsy, they get chemotherapy and they pass away,” says Morris. “We build the avatar, but the patient can’t use it.”