Exploring the Role of Microbes in Cancer Growth and Treatment

The human body is a thriving habitat for other life forms. Diverse communities of microbes that can be both good and bad for our health live in the gut, mouth, nose, and skin. But in recent years, microbes have found a more surprising place- cancers. Cancers are commonly thought of as simple masses of a patient's cells that malfunction and grow uncontrollably. They are communities of many different cell types in the environment surrounding cancer cells. It is one of the reasons why cancers are so hard to treat (1^✔ ✔Trusted Source
Microbes and Cancer

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Until recently, the role that these microbes play in tumors has not been clearly understood. Now scientists are starting to understand whether these tumor-associated microorganisms are accomplices that help in cancer cell development or just unfortunate bystanders. The answers could provide new approaches to treating and preventing cancers.

Studies Offer an Exciting Hint of What Might be Going on Between Microbes and Cancers

In a 2017 study, scientists showed that some bacteria living inside pancreatic cancers can protect the tumors by inactivating anticancer drugs. This helped the tumors become drug resistant. When they injected mice with colon cancer with the bacteria, the mice's cancers also became resistant to the drug. But when they gave an antibiotic alongside cancer treatment, the resistance disappeared.

Further to these findings, research published in 2019 looked retrospectively at patients suffering from advanced cancers who were treated with either an anti-cancer drug alone or those who also received an antibiotic to prevent or treat an existing infection.

They found that patients who were given an antibiotic had a better response to treatment. Although the study did not examine the number of bacteria present in the cancer tissue of these patients, it speculated that the antibiotics might have eliminated tumor-associated bacteria, which may have been interfering with the cancer treatment (2^✔ ✔Trusted Source
Microbes as Medicines: Harnessing the Power of Bacteria in Advancing Cancer Treatment

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Researchers are now hoping to build on these studies with a clinical trial involving patients with pancreatic cancer who failed their first-line treatment. But bacteria might also play other roles in cancer beyond protecting tumors from drug treatment.

In 2020 study involving more than 1,500 of seven different cancer types: breast, lung, ovary, pancreas, melanoma, bone, and brain. They found all cancers were invaded by bacteria, which lived inside the cancer cells and some of the immune cells. Different tumor types had distinct communities of bacteria.

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Each bacterium has adapted to the unique tumor micro-environment in which they live. In lung cancer, people who smoke have more bacteria that can degrade nicotine. In bone cancers, bacteria that metabolize hydroxyproline are mostly found.

Bacteria found in some types of breast cancer can detoxify arsenate, a type of carcinogen known to increase the risk of breast cancer. Others can produce a chemical called mycothiol, which helps to reduce levels of harmful reactive oxygen molecules that can damage DNA.

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There is growing evidence that tumor-dwelling bacteria may be making cancers worse. Some bacteria in breast tumors might make it easier for cancer cells to spread to other parts of the body.

The bacteria may also change the ability of the immune system to target and destroy cancer cells. Much more studies are needed to find the effects of bacteria inside tumors on the course of cancers (3^✔ ✔Trusted Source
Current understanding of the intratumoral microbiome in various tumors

Go to source). In many cases, it is still unclear whether the bacteria are helping the sufferer by keeping the cancer cells under control.

It may seem tempting to include antibiotics in cancer therapies, but it is not as simple as that. Many microbes are benign or even beneficial, so a brute-force antibiotic treatment could cause more harm than good.

Instead, researchers must try to unravel the full complexity of the tumor-associated micro-biome. Entire communities of microbes can be found within tumors, and they support each other in unexpected ways.

References:

1. Microbes and Cancer - (https://www.annualreviews.org/doi/10.1146/annurev-immunol-051116-052133)
2. Microbes as Medicines: Harnessing the Power of Bacteria in Advancing Cancer Treatment - (https://www.mdpi.com/1422-0067/21/20/7575)
3. Current understanding of the intratumoral microbiome in various tumors - (https://www.cell.com/cell-reports-medicine/fulltext/S2666-3791(22)00448-7)

Source-Medindia