Recent research reveals T cells and Natural Killer (NK) cells may respond to cancer cells differently and could ultimately provide more cancer treatment options.
A leading immunotherapeutic approach to treating cancer involves the use of checkpoint inhibitors. Immune checkpoints are proteins expressed on T cells and are essential for the self-tolerance needed to prevent autoimmunity. When T-cell checkpoint molecules bind to its ligand on cells, the targeted cell is not harmed. These checkpoints are often exploited by tumor cells by possessing checkpoint molecules such as PD-L1 and impeding the immune system’s ability to initiate and carry out an immune attack on the tumor.
The use of checkpoint inhibitors is heavily studied as a viable approach to support anti-tumor immunity. Studies of checkpoint inhibitors have heavily focused on their effects on T cells. These drugs are antibodies that allow T cells to recognize and mount an immune response against tumor cells. Examples of available drugs include: Pembrolizumab which targets PD-1, Atezolizumab which targets PD-L1, and Ipilimumab which targets cytotoxic T-lymphocyte-associated protein 4 and CTLA-4.
However, new research has shown that natural killer cells are also targeted by checkpoint inhibitors. Mice void of anti-tumor T cells were found to respond favorably to treatment with checkpoint inhibitors. However, when the mice were depleted of natural killer cells, the response to checkpoint inhibitor treatment was negatively affected, lowering the anti-tumor effects. The study results also show that natural killer cells have the same checkpoint molecules found on T cells.
The research findings show that both natural killer and T cells are essential for the PD-1 and PD-L1 blockade provided by checkpoint inhibitor immunotherapy. Further, combining the anti-tumor activity of natural killer and T cells may be particularly useful in patients who do not respond to current therapies. Patients’ tumors can be analyzed to determine their immune status and how the immune cells and factors of a particular patient interact and respond to tumors. This personalized medicine approach can provide cancer treatment approaches designed for the individual patient.
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The Ottawa Hospital. (2018, September 10). Often-overlooked Natural Killer cells may be key to cancer immunotherapy. ScienceDaily. Retrieved October 4, 2018 from www.sciencedaily.com/releases/2018/09/180910160648.htm