Immunity: Yogurt is not harmless!

Yogurt has a history of nearly 5,000 years as a daily drink for people
.

It is rich in lactic acid bacteria, protein, calcium, carbohydrates and various trace elements

However, not long ago, this kind of healthy food that people thought was "harmless to humans and animals" was labeled as a "cancer accomplice"
.

A new study shows that lactic acid bacteria, a type of bacteria thought to promote gut health, can promote tumor growth by affecting the metabolism of tryptophan and thus the function of macrophages

The study, published in the journal Immunity in February this year, is titled " Tryptophan-derived microbial metabolites activate the aryl hydrocarbon receptor in tumor-associated macrophages to suppress anti-tumor immunity ", which is translated into Chinese as "tryptophan-derived microbial metabolites".
Activation of aryl hydrocarbon receptors in tumor-associated macrophages to suppress antitumor immunity"
.

The research team is from the University of Toronto School of Medicine

Tryptophan-derived microbial metabolites activate the aryl hydrocarbon receptor in tumor-associated macrophages to suppress anti-tumor immunity Tryptophan-derived microbial metabolites activate the aryl hydrocarbon receptor in tumor-associated macrophages to suppress anti-tumor immunity

Figure 1 Research results (Source: Immunity)

Figure 1 Research results (Source: Immunity)

This work focuses on studying the inverse association of the microbiome with cancer and shows that under certain circumstances, the components of the microbiome may negatively impact cancer treatment
.

We examined the effect of AHR (aryl hydrocarbon receptor) on associated macrophage (TAM) function in pancreatic ductal adenocarcinoma (PDAC)

In long-term PDAC survivors, increased microbiome diversity correlates with TME (tumor-associated macrophage) survival and immunological profile
.

Reported fecal transplantation studies in mouse models have also shown that the microbiota can promote or inhibit tumor progression and affect TME cell composition

And, pan-cancer analysis showed that patients with PDAC (pancreatic ductal adenocarcinoma) exhibited higher AHR compared to most cancer types
.

In PDAC patients, high AHR expression is associated with rapid disease progression, mortality, and an immunosuppressive TAM phenotype

The authors further note that first-in-human clinical trials targeting AHR have been initiated in patients with advanced solid lung, colorectal, and urothelial tumors to examine the presence of AHR inhibition in multiple cancer types
.

Ultimately, these trials will provide a definitive test of whether AHR is a legitimate target for cancer treatment

Although pancreatic cancer is relatively rare, it is the third most deadly cancer in Canada
.

Over the past three decades, patients with the disease have not seen the same improved survival seen with other cancers

Overall, the specific mechanism by which Lactobacillus promotes cancer growth can be described as follows: Lactobacillus metabolizes tryptophan to indole, a metabolite produced by tryptophan metabolism that activates AHR
.
AHR is also a component of macrophages.
As immune cells of the human body, macrophages play an important role in tumor growth and metastasis
.
Therefore, the higher the AHR expression, the smaller the inhibitory effect on tumor growth
.

The yogurt we often drink contains a lot of lactic acid bacteria.
Although these probiotics are very helpful to our intestinal health, at the same time, this is also a kind of bacteria that has a potential threat to our body.
It deserves people's attention
.

Original source:

Original source:

Hezaveh K, Shinde RS, Kl? tgen A, et al.
Tryptophan-derived microbial metabolites activate the aryl hydrocarbon receptor in tumor-associated macrophages to suppress anti-tumor immunity.
Immunity.
2022 Feb 8;55(2):324-340.
e8.
doi: 10.
1016/j .
immuni.
2022.
01.
006.
PMID: 35139353; PMCID: PMC8888129.

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