By Megan Leinenbach
While we usually think of salt as just another tasty ingredient found on our kitchen tables, it has actually played a variety of important rolesthroughout human history. In fact, salt used to be a form of currency in the Roman empire, a lucrative trading good in Italy, and its preservative properties led to dramatic improvements in food storage. One could say that salt is a “jack of all trades”, and new research shows that it might also improve cancer treatment.
A 2019 paper titled “High Salt Inhibits Tumor Growth by Enhancing Anti-tumor Immunity”describes how a high salt diet can limit tumor growth in mice and in human cancer cells. The researchers concluded that high salt concentrations significantly inhibited tumor growth in both mice and human cells by blocking the activity of myeloid-derived suppressor cells (MDSCs). MDSCs are important players in the tumor microenvironment and are a double threat to cancer patients: not only do MDSCs help tumors grow by forming new blood vessels, but they suppress the immune system of patients. More specifically, MDSCs inhibit the function of important immune cells in mice and humans, like T cells and B cells, which attack foreign and self-antigens in the body.
While MDSCs rule the tumor microenvironment, high salt concentrations could be their weakness, as a high salt diet in mice inactivated MDSCs near the tumor. Consequently, the mice that were fed a high salt diet saw significantly slower tumor growth than mice that were fed a normal diet. These findings could be important to the treatment of cancer, specifically cancer immunotherapy, a method of treatment that uses the natural abilities of the immune system to fight cancer. In addition to slowing tumor growth in mice, high salt diets were able to inhibit MDSC function in human cancer cells. Indeed, the activity of immunosuppressive MDSC cells was almost entirely blocked in human cancer cells. This data shows that increased sodium concentrations of a high salt diet can make MDSCs less effective, not only slowing tumor growth, but also strengthening the immune system of a cancer patient. This is a significant finding because one of the greatest difficulties associated with cancer immunotherapy is that cancer patients often have weakened immune systems, partially due to the accumulation of MDSCs near the tumor.
While these results may prove useful for cancer immunotherapy in the future, we should keep in mind that salt has already been associated with health risks. Researchshows that excessive salt intake can lead to cardiovascular disease, chronic kidney disease, osteoporosis, and stomach cancer. Even though this study demonstrated the benefits of a high salt diet in mice and human cells, it is important to keep in mind that increasing sodium intake has negative health effects as well.
Nonetheless, these results have given medical professionals another tool in their toolbelt when it comes to managing tumor growth: manipulating salt concentrations. While eating a diet high in salt may not be the best way to take advantage of salt’s anti-tumor effects, this mechanism could be used in the future to block MDSC function in cancer immunotherapy.
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