Most cancers are inflamed (hot tumors) and under the right conditions can be controlled by T-cells. According to a recent article in Genetic Engineering and Biology News, there is another type of cancer whereby tumors are not inflamed. They are called “cold” tumors. These tumors can escape the body’s immune system and are not affected by immunotherapies.
About Regulatory T Cells
Regulatory T cells are instrumental in regulating and suppressing other cells in the immune system. There are two types of regulatory T cells (Tregs). The most important cell in the adaptive immune system is a type of white blood cell called the helper T cell (CD4). As the name implies, the helper cells assist other cells in creating an immune response. The term ‘adaptive’ is used because it responds to any type of disease-causing microorganism (pathogen) that invades the body.
The helper cells assist B cells in discharging antibodies and macrophages as they destroy bacteria and viruses (antigens). The helper cells work with the second type of T cells (cytotoxic T cells) that kill virally infected target cells. T cells recognize and respond to signs of inflammation in “hot’ tumors. They infiltrate the tumors and attack cancer.
Hot tumors are more easily affected by immunotherapy drugs which strengthen the immune system response.
Overcoming Resistance to Radiation Therapy
In a recent study, the University of Colorado researchers discovered that Tregs were suppressing the immune response. The study has been published in the Journal for ImmunoTherapy of Cancer.
The new discovery paves the way to solving a significant problem that occurs in clinical trials that treat head and neck squamous cell carcinomas (HNSCC). The researchers noted that the trials that combine immunotherapy and radiation therapy to treat cold tumors are failing. Cold tumors have proven to resist radiation therapy.
About the Study
The research team studied T cells’ role in tumor treatment. The team considered various therapeutic mechanisms to overcome resistance to RT checkpoint inhibitors. Using resistant cold models of HNSCC that were resistant to RT-checkpoint inhibitors, they observed distinguishing characteristics of the cells such as molecules and blood vessels that support other cells and tissues.
Co-study leader, Dr. Sana Karam, said that their findings indicated that the cells that normally instruct T cells to attack cancer were actually preventing the T cells to go on the offensive.
Dr. Michael Knitz who also led the study added that Tregs usually regulate T cells by preventing autoimmune disease. However, at times Tregs can become overly suppressive and completely silence T cell response.
The team experimented with medication to deactivate the Tregs. This helped raise the immune response to cold tumors.
Another discovery pertained to radiation treatments. The researchers found that the injuries caused by radiation treatments are sufficient for dendritic cells to activate regular T cells causing them to go into attack mode.
The effect explains Dr. Karam is similar to a vaccination. The dendritic cells activate the immune system causing it to produce an abundance of T cells which in turn kill cancer. Dendritic cell activation allows radiation to heat the cold tumors.
Dr. Karam was adamant that something must be done for patients with cold tumors. She explained how destructive they are to muscle and bone, to the tongue, gum, jaw, and lymph nodes. Dr. Karam said that the tumors are similar to those tumors resulting from years of heavy smoking.
Dr. Karam describes the disease as “horrible” and said that there is a high failure rate. Many times the treatment involves removal of the tongue followed by weeks of chemotherapy and radiation with poor results.
She reiterated that they must do better for these patients.