BALTIMORE – Megan Sykes, a medical researcher, has a mouse with a human immune system – her own. She calls it “Mini-Me.”
There are also mice containing a part of 9-year-old Michael Feeney – a cancerous tumor extracted from his lungs. Researchers have tested various drugs on the mice, hoping to find the treatment that would work best for Michael.
In what could be the ultimate in personalized medicine, animals bearing your disease, or part of your anatomy, can serve as your personal guinea pig, so to speak. Some researchers call them avatars, like the virtual characters in movies and online games.
“The mice allow you the opportunity to test drugs to find out which ones will be efficacious without exposing the patient to toxicity,” said Colin Collins, a professor at the University of British Columbia.
Experiments on mice have been done for decades, including implanting people’s tumors into the animals. But the techniques have improved in the last few years, and interest is growing. The National Institutes of Health sponsored a workshop on personalized animal models earlier this month. And while the models are mainly being used for research, companies are beginning to commercialize them for use in drug development and medical treatment as well.
Experts caution that it has not been proved that the use of avatars will prolong the lives of cancer patients. And it costs tens of thousands of dollars, which insurers will not cover, to create and test a colony of the animals.
“It’s an act of faith to say this is a superior way of proceeding,” said Dr. Edward Sausville, an expert on mouse models of cancer at the University of Maryland.
But some cancer patients, wanting to try everything possible, are turning to the mice anyway.
“This just seems right to us,” said Jill Feeney, the mother of Michael, who has been fighting a type of bone cancer called Ewing’s sarcoma since 2009, when he was 6. “It’s actually his tumor growing somewhere, and we’re treating it the way he would be treated.”
When Michael had surgery in February to remove a tumor that had spread to a lung, a courier was waiting outside the operating room in New York to whisk the tumor to a laboratory here run by a company called Champions Oncology.
Four hours later, technicians cut the tumor into five pieces and placed each piece under the skin of an anesthetized mouse. Two months later, after the tumors had grown, they were removed, cut into pieces and each piece implanted into another mouse. A month later there were enough mice models to begin testing.
The Feeneys, who live in Ridgewood, N.J., paid $25,500 for the creation of the avatars and the testing of four different drugs or drug combinations.
The results came back in July. A combination of four drugs – gemcitabine, docetaxel, Avastin and Afinitor – was “astonishingly active” in shrinking the tumor in the mice, said Michael’s oncologist, Dr. Leonard H. Wexler of the Memorial Sloan-Kettering Cancer Center. Wexler said that the combination was not something oncologists would typically choose.
Michael has not tried the combination yet because he is participating in a clinical trial of an experimental drug. But if that drug does not work, his mother said, “we have the home run in the back pocket.”
Cancer is not the only area where the animal models may be useful.
Sykes, a professor at Columbia, led the team there and at Massachusetts General Hospital that replicated an individual’s immune system in mice using a bone marrow sample from the person’s hip.
The immediate goal is to study how Type 1 diabetes, an autoimmune disease, develops. But in the future, she said, such “personalized immune mice” might produce immune cells that can be transplanted into the patient to help fight disease.
At Washington University in St. Louis, Dr. Jeffrey Gordon has transplanted the collection of bacteria in a person’s intestines into mice. The “humanized” mice might be used to study, for instance, how a change in diet could influence the person’s health.
In cancer, drugs that work in mice do not always work in people. But some studies suggest that tumors freshly implanted from patients more closely resemble human disease than those created by the common technique of implanting tumor cells that have been cultured in a laboratory dish.
“It’s the closest we can get to the real deal,” said Alana Welm, a breast cancer researcher at the University of Utah.
Still, the stand-ins are not perfect surrogates. A tumor implanted under the skin of a mouse might not behave the same as it did in the human breast, lung or other organ from which it was extracted. Unlike people, the mice are bred to have a deficient immune system, so they will not reject the human tumor.