Previously regarded merely as an immune system helper, a kind of white blood cell now seems to be the initiator of the body’s defenses against cancerous tumors.
The finding could improve cancer immunotherapy, a promising treatment that targets cancer cells using the body’s own immune system rather than radiation.
A type of T cell known as CD4-positive helper T cells was identified by researchers. These T cells contributed to the development of a series of antitumor immune mechanisms that enable killer cells to more thoroughly infiltrate melanoma and breast cancer tumors.
The finding could improve cancer immunotherapy, a promising therapy that targets cancer cells using the body’s own immune system rather than radiation.
Previously regarded merely as an immune system helper, a kind of white blood cell now seems to be the initiator of the body’s defenses against cancerous tumors. The finding could improve cancer immunotherapy, a promising treatment that targets cancer cells using the body’s own immune system rather than radiation.
Researchers from Washington State University discovered in an animal study that a population of T cells known as CD4-positive helper T cells contributed to the initiation of a chain of antitumor immunity defenses that improves the ability of killer cells to infiltrate melanoma and breast cancer tumors. T cells are a subset of white blood cells called lymphocytes, which circulate all throughout the body via the lymphatic system.
The involvement of a specific subset of killer cells known as CD8-positive T cells has been the focus of several prior studies as well as contemporary immunotherapies. However, fewer than 20% of patients react to such treatments, and Hui Zhang, the study’s lead author, suggested that the CD4-positive helper cells’ initiating role could improve those treatments. The findings were recently published in the Journal of Immunology.
“One of the most challenging parts of current cancer immunotherapy is the low response rate,” said Zhang, a WSU assistant professor of pharmaceutical sciences. “The lack of knowledge of how to enhance lymphocyte infiltration into the tumor hampers the success of improving the response rate to cancer immunotherapy. Our finding shows promise in solving this problem.”
Cancer is the second leading cause of death both nationally and worldwide. Currently, surgery, chemotherapy, and radiation therapy are the conventional approaches to cancer treatment. However, those approaches cannot cure many cancers because some become metastatic, spreading from the primary tumor throughout the body, and certain cancer stem cells can become resistant to chemotherapy and radiation.
A relatively new treatment, immunotherapy has shown promise in curing a range of cancers, but only a relatively low number of patients respond to it. Zhang’s research team hopes to change that with the knowledge of the mechanisms that help start the body’s immune defenses.
The immune system has two types of killer cells: the CD8-positive T cells, and so-called “natural killer” cells. Both can attack virally infected cells and cancer cells.
Natural killer cells are innate and roam around the body. They act as the first line of defense in our immune system but cannot recognize specific antigens – toxins or other foreign substances in the body – on their own. After the natural killer cells start to work, the CD8-positive T cells, which can recognize specific antigens, arrive. While CD8-positive T cells and their mechanisms have been well studied and are used in current immunotherapies, not much is known about how to activate natural killer cells’ antitumor function.
Using genetic knock-out mice experiments, Zhang’s group found evidence that a certain type of CD4-positive T cells, called tissue-resident memory T cells, may be critical in activating those first lines of natural killer cell defenders. Their experiments showed that they were effective against both melanoma and breast cancer tumors.
“We found that this specific population of CD4 T cells were the key player to initiate the antitumor immunity,” said Zhang.
The specific CD4 T-cells together with the natural killer cells not only killed tumor cells and controlled tumor progression but also enhanced infiltration of other white blood cells, or lymphocytes, into the tumor.
In future studies, the researchers plan to continue to investigate the precise cellular and molecular mechanisms of this antitumor immunity.