Could one shot administered directly to a solid tumor mark the end of cancer?
Research devising more effective treatments for all types of cancer has been abundant over the past few years, offering new hope all the time.
The latest study, from Stanford University School of Medicine in California, has investigated the potential of yet another approach: injecting "minute" amounts of two agents that stimulate the body's immune response directly into a malignant solid tumor.
So far, their studies using mice have proven successful. "When we use these two agents together," explains senior study author Dr. Ronald Levy, "we see the elimination of tumors all over the body."
"This approach bypasses the need to identify tumor-specific immune targets and doesn't require wholesale activation of the immune system or customization of a patient's immune cells."
Dr. Ronald Levy
Moreover, the researchers have reason to believe in a speedier trajectory toward clinical trials for this method, since one of the agents involved has already been approved for use in human therapy, while the other is already under clinical trial for lymphoma treatment.
The study's findings were published yesterday in the journal Science Translational Medicine.
'One-time application' of formula
Dr. Levy specializes in the use of immunotherapy — which is a type of treatment wherein the body's immune response is enhanced so that it can target cancer cells — to fight lymphoma, or cancer of the lymphatic system.
There are several types of immunotherapy, including some that boost the entire immune system of the body and others that are a lot more targeted. But, the researchers note, they all come with caveats attached.
They may have problematic side effects, be time-consuming, or be simply too costly. The team's method, however, arguably has more benefits — even beyond its potential effectiveness as a treatment.
"Our approach uses a one-time application of very small amounts of two agents to stimulate the immune cells only within the tumor itself," Dr. Levy explains. This method can "teach" immune cells how to fight against that specific type of cancer, which then allows them to migrate and destroy all other existing tumors.
Although the immune system's role is to detect and eliminate harmful foreign bodies, many types of cancer cell are able to evade detection in complex ways, which enables them to grow and spread.
A type of white blood cell called T cells play a vital role in regulating the body's immune response. Normally, T cells would target and fight cancer tumors, but all too often, cancer cells learn to "trick" them and escape the immune response.
Effective against many types of cancer
In the new study, Dr. Levy and his team delivered micrograms of two specific agents into one hard tumor site in each of the affected mice. The agents in question were:
- CpG oligonucleotide, a short stretch of synthetic DNA that boosts the immune cells' ability to express a receptor called OX40, which is found on the surface of T cells
- an antibody that binds to the receptor, activating the T cells
Once the T cells are activated, some of them migrate to other parts of the body, "hunting down" and destroying other tumors.
Importantly, Dr. Levy and his colleagues note that this method could be used to target a number of different kinds of cancer; in each case, the T cells will "learn" to deal with the specific type of cancer cell that they have been exposed to.
In the laboratory, the scientists first applied this method to the mouse model of lymphoma, and 87 out of 90 mice became cancer-free. In the other three cases, the tumors did recur, but they disappeared when the researchers administered the treatment a second time.
Similarly successful results were observed in the mouse model of breast, colon, and skin cancer. Also, even the mice that were genetically engineered to develop breast cancer spontaneously responded well to this method of treatment.
'A targeted approach'
However, when scientists transplanted two different types of cancer tumor — lymphoma and colon cancer — in the same animal but only injected the experimental formula into a lymphoma site, the results were mixed.
All the lymphoma tumors did recede, but the same did not hold true for the colon cancer tumor, confirming that the T cells only learn to deal with the cancer cells that were in their immediate vicinity before the injection.
As Dr. Levy continues, "This is a very targeted approach. Only the tumor that shares the protein targets displayed by the treated site is affected. We're attacking specific targets without having to identify exactly what proteins the T cells are recognizing."
Currently, the team is preparing a clinical trial to test the effectiveness of this treatment in people with low-grade lymphoma. Dr. Levy hopes that, if the clinical trial is successful, they will be able to extend this therapy to virtually any kind of cancer tumor in humans.
"I don't think there's a limit to the type of tumor we could potentially treat, as long as it has been infiltrated by the immune system," Dr. Levy concludes.