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How Gut Bacteria May Soon Carry Anti-Cancer Drugs

In the last few decades, humanity’s relationship with bacteria has evolved a great deal, as we learn more about how interconnected we are.

In the 20th century, antibiotics were one of the greatest discoveries — a series of powerful methods for destroying bacterial invaders.

More recently, however, we’re seeing more benefits to keeping bacteria around. New research into the complex populations of bacteria that live in, on and around us, the microbiome, reveal our dependence. Bacteria help us avoid disease, break down food in our digestive tract, produce compounds and nutrients we absorb, and keep our immune system trained and regulated.

Could we train our partner bacteria to go further? Could they help us to fight cancer?

A new paper in the journal Microbiome offers a glimpse into a new world — where bacteria help deliver compounds to suppress tumor growth to the lower digestive tract, helping to fight colon cancer.

Half the Battle is Delivering the Medicine

It can be especially challenging to take an oral dose of medicine.This can make it especially difficult to treat diseases such as colon cancer; the medicine has to survive its trip through nearly the entire digestive system.

There are a number of different vectors that can be used to help ensure that medicine releases its proper destination. Some capsules, for example, are extended release to ensure that they do not dissolve and dump their medicine payload too early in the digestive tract.

But what if we used bacteria? What if we tapped the gut microbiome in order to help us treat cancer?

The microbiome is already a topic of open study during the treatment of cancer, especially if someone is on chemotherapy. Chemotherapy targets and destroys actively dividing cells, and it does a lot of damage to the microbiome. It can kill off the bacteria, and can have long-term impacts on the fungi present in a normal microbiome.

Instead of using broad scale chemotherapy, however, another hypothesis is that we use specialized, targeted treatments, carried by helper bacteria.

In a 2021 paper, researchers at Yonsei University in South Korea modified a probiotic bacterium called Pediococcus pentosaceus, which is well characterized as feeding off lactic acid. The researchers modified this bacterium to produce a therapeutic protein, P8, that impairs and reduces tumor growth. Does this bacterium-secreted therapeutic protein help with cancer?

It seems to do so! The researchers tested this modified P. pentosaceus bacterium by feeding it to mice that had grafted-in colorectal cancer. Compared to mice that did not consume this probiotic, the probiotic-fed mice showed reduced tumor volume and inhibited tumor growth.

Normally, these chemicals cause disruption to the gut microbiome, along with spurring the growth of tumors. But in the probiotic-dosed mice, the microbiome showed reduced damage from the addition of these chemicals as well.

There are a few interesting results from this:

  1. These bacteria are able to synthesize and secrete customized proteins.
  2. These bacteria are able to survive their journey through the intestinal tract, still putting out the P8 protein into the environment. It seems that they’re able to not just produce the protein, but deliver it to the tumor cells.
  3. These bacteria were able to help protect the gut microbiome from disruption due to the presence of tumor-inducing, neurotoxic chemicals.

Overall, in the probiotic-dosed mice, the researchers observed increased body weight, better survivability, and longer colon length — all positive indicators that help improve recovery from cancer.

Is this Bacterium Going to be the Next Anti-Cancer Silver Bullet?

We are able to cure many more cancers in mice than we are in ourselves; many molecular approaches to mouse tumors simply do not work on a different organism (such as Homo sapiens).

However, this study does highlight three important lessons:

Targeted anti-cancer treatments are better, when they can reach their targets

Many big breakthroughs in cancer treatments, allowing people diagnosed with cancer to not see it as a death sentence, are due to the development of better, more targeted chemotherapies.

Typical broad-range chemotherapy, the chemotherapies of the 80s and 90s, focused on killing all actively dividing cells.

Protecting the microbiome during cancer may help lead to better health outcomes

As mentioned above, broad chemotherapy kills actively dividing cells. This means it also does a nasty number on the microbiome.

We know from a wide range of studies that the microbiome contributes in many ways to overall health.

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