Our immune systems hold the power—the power, that is, to treat cancer. Composed of various types of cells, tissues, and organs, the immune system serves as more than the body's main defense against foreign invaders such as bacteria and viruses.
According to a study conducted by researchers at the Stanford University School of Medicine, injecting microscopic amounts of two immune-stimulating agents into solid tumors in mice can erase all traces of cancer in the animals. These cancer injections may also eradicate distant, untreated metastases.
Researchers believe minute applications of the agents may serve as a rapid and somewhat inexpensive form of cancer therapy with minimal side effects compared to full-body immune stimulation. “When we use these two agents together, we see the elimination of tumors all over the body,” said Ronald Levy, MD, professor of oncology. “This approach bypasses the need to identify tumor-specific immune targets and does not require wholesale activation of the immune system or customization of a patient's immune cells.”
One out of two of these agents gained approval for human use, while the second is still being tested for human use in unrelated clinical trials.
Cancer Immunotherapy consists of harnessing the capability of the immune system to combat cancer. Some methods rely on stimulating the immune system throughout the body, while others focus on naturally occurring checkpoints that restrict the anti-cancer activity of immune cells. Methods such as the CAR T-cell therapy remove the patient's immune cells for genetic engineering, allowing them to attack tumors in cells after re-insertion.
Though many of these approaches have been successful, they each have their challenges and downsides, including high costs and lengthy treatment preparations.
“All of these immunotherapy advances are changing medical practice,” Levy said. “Our approach uses a one-time application of very small amounts of two agents to stimulate the immune cells only within the tumor itself. In mice, we saw amazing, body-wide effects, including the elimination of tumors all over the animal.”
Cancer often takes on a confusing role concerning the immune system. Immune cells such as T-cells recognize and attack the abnormal proteins frequently present with cancer tumors. Unfortunately, the tumor often formulates a way to suppress the activity of these cells as it grows. Levy's method aims to reactivate the T-cells by injecting minimal amounts of two agents directly into the tumor. One agent, called CpG oligonucleotide, works with other immune cells in proximity to expand the creation of an activating receptor termed OX40 on the exterior of the T-cells. The second agent is an antibody that binds to OX40 and activates T-cells to combat cancer cells. Some activated T-cells then exit the original tumor to find and destroy other equal tumors throughout the body.
Effect on Animal Cancers
This approach has been tested on laboratory mice with transplanted mouse lymphoma tumors in two areas of the body, working significantly well. The results showed that injecting one tumor site with both agents resulted in the regression of the treated tumor and the second untreated tumor. Following this procedure, 87 out of 90 mice were cured of cancer. The three remaining mice with recurring cancer received a second treatment, curing their tumors. Mice with breast, colon, and melanoma tumors bore similar positive results.
The current clinical trial expects to recruit about fifteen individuals with low-grade lymphoma. Levy believes the treatment could be helpful in many tumor types if successful. “I do not think there is a limit to the type of tumor we could potentially treat, as long as the immune system has infiltrated it,” Levy said. Levy hopes for a future where clinicians inject the two agents into solid tumors in humans before surgical removal of cancer as means to block recurrence due to unidentified metastases or lingering cancer cells.