A study by an international research team led by professor Markus Kleinewietfeld (VIB-UHasselt) shows that high salt intake inhibits tumor growth in mice. The effect seems to be due to a change in function of certain immune cells that play a critical role in cancer immunity. The further exploration of this finding might be beneficial for improving anti-cancer immunotherapies.

Salt impacts experimental tumor models

High salt intake is a known risk factor for high blood pressure and cardiovascular diseases. Recent research has also indicated that too much salt may impact autoimmunity. Studies have shown that a high-salt diet could change the immune cell balance towards a more aggressive state and worsen autoimmunity. Interestingly, these shifts in the immune cell balance, though detrimental in autoimmune conditions, could be, in theory, useful in anti-cancer immune therapies to improve immune attacks against tumor cells.

An international research team led by Kleinewietfeld that included professor Sven Brandau (University of Duisburg-Essen?, Germany), Dr. Thomas Kammertöns (Charite & MDC-Berlin, Germany), and professor Jo Van Ginderachter (VIB-VUB) have now investigated the impact of high salt intake on tumor growth in mice. They found that a high-salt diet inhibited tumor growth in two independent mouse models. The research team further found that this effect seemed to be related to a change in the functions of certain immune cells, so called myeloid-derived suppressor cells (MDSCs). MDSCs are believed to hinder other immune cells to efficiently attack and eliminate tumor cells.

Immune cells changing function

When the researchers mimicked a salty environment in cell culture, they observed a functional change in MDSCs. The cells were less capable of inhibiting other immune cells. A similar modulatory effect of high-salt conditions on MDSCs was observed with cells isolated from human cancer patients. Moreover, if these cells were depleted, the effect of a high salt diet on tumor growth in mice was undone. MDSCs are suspected to be an important mechanism that prevents an efficient immune attack against tumors in anti-cancer immunotherapies. The underlying molecular mechanism that blocks the function of these cells could therefore have therapeutic potential. However, since high salt intake is suspected to be a risk factor for gastric cancer in humans, the findings of this study and molecular mechanisms behind them must be carefully analyzed in future studies. Says Kleinewietfeld, “The findings are highly interesting, and we were surprised to see such an effect on tumor growth just by increasing the salt in the diet. However, future studies are needed to fully understand the effect and the detailed underlying molecular mechanisms behind to judge its therapeutic potential for anti-cancer immunotherapies.