A vaccine made of stem cells taught the immune systems of mice to fight , in a study that may pave the way to preventing the disease in humans.
Stem cells share similarities with cancer, so researchers used them to teach the bodies of the mice to recognize and fight the disease.
The 'vaccine,' developed by researchers at Stanford University, plus an immunity-boosting agent shrunk tumors in the majority of the mice, and two of them beat the cancer entirely.
The scientists say that their new method shows promise as a personalized way to someday preventatively immunize humans against their own cancers.
Cancer occurs when cells start multiplying and growing out of control. Scientists discovered that, as healthy cells undergo this change, they revert back to a state very similar to their early development stages.
Vaccines work to prevent infections by introducing a similar but less harmful germs to the body so that our immune systems get a sort of primer course on what these illnesses look like and how to fight them.
So the Stanford researchers posited that the pre-cancer-like developmental cells could work in much the same way, preparing immune cells to be on high alert for cells that might be ready to turn to tumors.
To test their theory, they used easy-to-extract skin and blood cells from mice to create induced pluripotent stem (iPS) cells by giving them a sort of genetic bath that rewound their developmental clocks.
These are sometimes called 'master' cells because, in the early stages of a fetus's development, pluripotent cells are poised to morph into any kind of tissue.
Because they are so malleable, they can also turn into a type of tumor called a teratoma - which is essentially a set of random tissues that develops in places in the body where none of those tissues belong.
If iPS cells can become a teratoma they can also become just about any other kind of cell, so the researchers made sure the reverted mouse cells could do so, then blasted them with radiation to make sure they wouldn't once they were injected back into the animals.
The researchers tested their inoculation idea on four groups of mice: one set got a placebo injection, another got just the specially prepared iPS 'vaccine' made from their own cells, one group got just an immunity-booster (called an adjuvant and used to improve the effectiveness of many vaccines) and group got a combination of the vaccine and the booster.
Once the mice had been inoculated (or not, in the case of the control group), the study authors transplanted breast cancer cells into them and waited to see if the iPS cells had taught their bodies to put up a fight.
When combined with the immunity-boosting adjuvant, the iPS vaccination shrunk tumors in seven out of the 10 mince that got that treatment.
The treatment was so effective that the immune systems of two mice performed perfect search and destroy missions, fully 'rejecting' the tumors that had begun to grow.
"Once activated, the immune system is on alert to target cancers as they develop throughout the body," said lead study author Dr
Nigel Kooreman.
Those two went on to live healthily for another year – a full life, considering that mice typically only survive two to three years in labs.
Shrinking tumors and improved survival rates meant that introducing the iPS cells taught cancer-killing T cells to find and kill the faulty, diseased cells.
"When we immunized an animal with genetically matching iPS cells, the immune system could be primed to reject the development of tumors in the future," said senior study author and profess of cardiology and radiology, Dr Joseph Wu.
"Pending replication in humans, our findings indicate these cells may one day serve as a true patient-specific cancer vaccine."
Because each mouse was injected with a vaccine made from its own, genetically-identical cells, there was very little risk that the immune system would attack the iPS cells before it had a chance to learn to kill cancer.
"Reprogramming the immune system to stop the development of tumors may save countless numbers of lives as well as spare many from grueling, debilitating treatment," said Jane Murphy, a clinical nurse specialist at Breast Cancer Care in the UK said.
The anti-cancer shot could also be rejection-proof and personalized, offering fewer risks and better efficacy for possible future patients.
"Although much research remains to be done, the concept itself is pretty simple," Dr Wu said. "We would take your blood, make iPS cells and then inject the cells to prevent future cancers. I'm very excited about the future possibilities."