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About ten years ago I had breakfast with my father when he noticed that I was pouring salt on my eggs. “Do you ever worry about your salt intake?” ” He asked. I sniffled derisively. “No. I don’t drink, I don’t eat red meat, I’m not going to worry about the salt,” I said.
As I got older, it became less true. Study after study, people on a high salt diet are at increased risk of high blood pressure, heart attack and stroke. (I haven’t actually cut back on salt, but at least I’m worried about it now.)
But a study published on Friday in Scientists progress suggests that high-salt diets may have something unexpected for them: tumor removal. Researchers looking at anti-tumor immunotherapy looked at the effect of high-salt diets in mice with tumors. It appears that a generally negative consequence of a high salt diet, inflammation, may actually help suppress tumor growth. The results could be promising for future cancer treatments.
Amit Awasthi, associate professor at the Translational Health Science and Technology Institute in India and one of the study researchers, recounts Reverse, “Salt has recently been identified as a trigger for the activation of the immune response and the promotion of the inflammatory response in autoimmune diseases.
“Therefore, we thought that the salt might be useful in overcoming the suppressive tumor microenvironment and thus promoting an anti-tumor immune response.”
The background- The study builds on existing research which suggests that salt plays a role in the immune system in addition to the cardiovascular system. A 2019 study published in Frontiers of immunology found that rodents fed a high salt diet “exhibited significantly inhibited tumor growth” compared to the control group.
But how exactly did the salt accomplish this? What was the process by which the salt shrunk the tumor? That’s what Awasthi and his colleagues wanted to know.
Does salt shrink tumors in mice?
What did they do- First, the researchers wanted to confirm that a diet high in salt could, in fact, inhibit tumor growth. So they implanted mice with B16F10 skin melanoma cells, then fed them one of three diets: a low-salt diet, a “normal” or medium-salt diet, and a high-salt diet (HSD).
What they found— Good news for people who hate cancerous tumors, researchers’ findings corroborated the 2019 Borders study: Tumors in mice given a high salt diet were significantly inhibited compared to those given a low salt diet or a normal salt diet.
Given the damage that salt can cause to other parts of the body, the researchers also wanted to see how the organs in mice performed on the high-salt diet.
Unexpectedly, the researchers say they found no toxicological effects on major organs, including the heart, lungs, kidneys, liver, or spleen.
How does salt shrink tumors in mice?
Dig into the details— To understand how and why the high salt diet caused tumor suppression, the researchers performed “extensive profiling of immune cells infiltrating the tumor, draining lymph nodes and splenocytes.” [white blood cells from the spleen or splenic tissue]. “
Researchers found that diets high in salt modulated the gut microbiome, which regulates crucial components of the immune system.
In particular, Awasthi says the researchers found that “HSD influenced the abundance of certain bacterial genera, including a significant increase in the abundance of Bifidobacterium. “
Bifidobacterium genus of intestinal bacteria play a beneficial role in various physiological pathways, especially in maintaining intestinal hemostasis.
Specifically, when the researchers profiled the cells, they found an almost 50% increase in natural killer (NK) cells, a type of white blood cell that can kill tumors.
Additionally, their results suggest that the salt acts as an adjuvant, something that modulates immune responses to a vaccine or other immunotherapy. In this case, the salt inhibited a molecule called PDL1 – a protein that works as a “checkpoint”, usually preventing T cells from attacking other cells in the body (when you have cancer in your cells, you want to these T cells to attack).
“The culmination of this work provides evidence that HSD-mediated tumor immunity depends on the interaction between Bifidobacterium and NK cell activity, ”Aswathi explains.
Although salt may have been the catalyst for these promising reactions, it seems that Bifidobacterium does a lot of the heavy lifting. Researchers fed mice normal, low-salt diets Bifidobacterium alone (without additional salt). They found that the bacteria were just as effective at reducing tumor burden in mice.
What this means for the future— Aswathi says it’s too early to know if high-salt diets might eventually be prescribed for people with certain cancers, but he thinks it’s “an interesting hypothesis to test.”
“HSD, despite its unwanted pathological effects, could be beneficial in conditions where one wishes to elicit an aggressive immune response,” he says.
When properly monitored, it may be possible to mitigate the negative consequences of HSD while harnessing its tumor suppressing power.
“An important finding from our study was that tumor-bearing mice, which ate a diet high in salt, had no pathological disease, which means that HSD is not only well tolerated but beneficial for an anti-tumor response, », Explains Aswathi.
The researchers’ findings could hold promise for cancer patients in several ways, alone or in combination with other therapies. But these possibilities “Must be tested in a clinical setting with controlled surveillance,” Aswathi warns.
And after- These human trials are what the researchers hope to do next.
“One avenue we would like to explore is randomized clinical trials of HSD in patients with solid tumor,” he says. “We would also like to extend the results of this study to understand ionic deregulation in inflammatory diseases. “
Although cancer immunotherapy – therapies that mimic some of the natural signals the body uses to control cell growth – has been researched for nearly a century, it has only become a major part of cancer treatments. cancer than in the last decade.
Aswathi and her team may have discovered the next major step in tumor immunotherapies, all thanks to a mineral that is likely in your kitchen cupboard.
Summary: A high salt diet (HSD) modulates effector and regulatory functions of T cells and promotes tissue inflammation in autoimmune diseases. However, the effects of HSD and its association with the gut microbiota in tumor immunity remain undefined. Here we report that HSD induces natural killer cell (NK) mediated tumor immunity by inhibiting PD-1 expression while enhancing serum IFN and hippurate. Salt enhanced tumor immunity when combined with a suboptimal dose of anti-PD1 antibodies. While HSD-induced tumor immunity was dulled upon depletion of the gut microbiota, transplantation of the fecal microbiota (FMT) of HSD mice restored tumor immunity associated with NK cell functions. HSD increased the abundance of Bifidobacterium and caused an increase in intestinal permeability leading to the intratumoral localization of Bifidobacterium, which improved NK cell functions and tumor regression. Intratumoral injections of Bifidobacterium activated NK cells, which inhibits tumor growth. These results indicate that HSD modulates the gut microbiome that induces tumor-dependent NK cell immunity with a potential translational perspective.
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