Staphylococcus epidermidis (left) and Micrococcus luteus (right) in a Petri dish. They are bacteria commonly found on human skin. Among them, Staphylococcus epidermidis was found to be genetically modified to treat cancer in the latest research. (Shutterstock)
Stanford Medicine researchers have made a valuable discovery that could lead to a new cancer treatment approach. Scientists are experimenting with changing the genomes of skin microbes and bacteria to fight cancer. The altered microbes were swabbed into cancer-bearing mice, and their tumors began to spread.
The study involved a bacterium called Staphylococcus epidermidis, which was extracted from the fur of mice and engineered to produce a protein that stimulates the immune system against specific tumours. Trials have been highly successful, with the modified bacteria dabbed onto fur killing an aggressive form of metastatic skin cancer without causing inflammation.
The study was published April 13 in the journal Science.
“It’s almost like magic,” says Michael Fischbach, Ph.D., associate professor of bioengineering at Stanford University. “These mice had very aggressive tumors on their sides, and we gave a gentle treatment of rubbing the bacteria on the scalp.”
Another exploration into the unknown world of microbes, the gut biome gets a lot of media attention these days, and the skin is home to millions of bacteria, fungi, and viruses for purposes that are rarely communicated.
In experiments, the scientists found that S. epidermidis cells stimulate the production of an immune T cell called CD8. Basically, the researchers manipulated S. epidermidis to generate CD8 T cells directed against a specific antigen, in this case, a specific antigen associated with skin cancer. When such T cells encounter a tumor with a matching specific antigen, they begin to multiply rapidly and shrink the tumor, or eliminate it completely.
“Watching these tumors spread step by step, and these bacteria were spread in a place far away from the tumor,” Fischbach said. “It took us a long time to believe it was true.”
As with all emerging cancer treatments, there are some important caveats to this new approach. First, these experiments were performed on mice. Humans and mice are biologically similar in many ways, but many treatments that work in mice do not work in humans. The Stanford researchers also don’t know if Staphylococcus epidermidis triggers an immune response in humans, even though it’s all over our skin, so they may have to find a different microbe eventually. Furthermore, this method is intended to treat skin cancer and is only suitable for topical use; we have to wait to see if it will be effective for cancer in the body.
That said, human trials are expected within the next few years, the Stanford team said, although more trials in mice and other animals will be needed before human trials can take place. Scientists hope the treatment could eventually target human cancer cells as well as various other infectious diseases. ◇#
Editor in charge: Ye Ziwei