Fasting, a commonly advised diet strategy for weight loss, is emerging as a potential tactic in combating cancer. Researchers have found that periods of fasting could boost the immune system's natural killer cells to fight off cancer.
A study conducted by the research team from the Memorial Sloan Kettering Cancer Center revealed an interesting link between fasting and the body's immune system, particularly natural killer (NK) cells.
NK cells are a type of white blood cell that can eliminate abnormal or infected cells, such as cancer or virus-infected cells, without prior exposure. Unlike T cells, they do not require previous encounters to respond. Having more NK cells in a tumor usually indicates a better prognosis for the patient.
According to the results of the mouse study findings published in the journal Immunity, fasting can alter the metabolism of natural killer cells, enabling them to survive the harsh conditions within and around tumors and improve their effectiveness in fighting cancer.
"Tumors are very hungry. They take up essential nutrients, creating a hostile environment often rich in lipids that are detrimental to most immune cells. What we show here is that fasting reprograms these natural killer cells to better survive in this suppressive environment," said immunologist Joseph Sun, a senior author of the latest study, in a news release.
During the trial, the mice with cancer followed a restricted eating regimen, fasting for 24 hours twice a week and then having unrestricted eating between the fasts.
The researchers observed that while this approach prevented weight loss in the mice, it significantly impacted their NK cells. Fasting also caused a redistribution of NK cells throughout the body. Many of these cells migrated to the bone marrow, where they encountered a lot of Interleukin-12, a crucial signaling protein. This boosted their production of Interferon-gamma, a cytokine crucial for fighting tumors. The fasting also resulted in the reprogramming of NK cells in the spleen, making them more efficient at using lipids for energy.
"During each of these fasting cycles, NK cells learned to use these fatty acids as an alternative fuel source to glucose. This really optimizes their anti-cancer response because the tumor microenvironment contains a high concentration of lipids, and now they're able to enter the tumor and survive better because of this metabolic training," Rebecca Delconte, who led the study, said.
"Our findings identify a link between dietary restriction and optimized innate immune responses, with the potential to enhance immunotherapy strategies," the researchers concluded.
