Traces of fungi growing in tumors could be linked to patient outcomes

Scientists have discovered traces of fungi lurking in the tumors of people with various types of cancer, including breast, colon, pancreas and lung cancer.

However, it is still not clear whether these fungi play a role in the development or progression of cancer.

Two new studies, both published in the journal Sept. 29 celldiscovered DNA from fungal cells hiding in tumors throughout the body.

In one study, researchers looked for genetic fingerprints of fungi in 35 different types of cancer by examining more than 17,000 tissue, blood and plasma samples from cancer patients.

Not every single tumor tissue sample tested positive for fungi, but overall the team found fungi in all 35 cancer types studied.

“Some tumors had no fungi at all, and others had a huge amount of fungi,” co-senior author Ravid Straussman, a cancer biologist at the Weizmann Institute of Science in Rehovot, Israel, told STAT; However, when tumors contained fungi, they often did so in “small amounts,” the team noted in their report.

Based on the amount of fungal DNA his team discovered, Straussman estimated that some tumors contain one fungal cell for every 1,000 to 10,000 cancer cells.

When you consider that a small tumor can be loaded with about a billion cancer cells, you can imagine that fungi “have a huge effect on cancer biology,” he said.

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Straussman and his team found that each cancer type tended to be associated with its own unique collection of fungal species; These included usually harmless fungi known to live in humans and some that can cause diseases like yeast infections.

These types of fungi, in turn, often coexisted with certain bacteria within the tumor. It is currently unknown if and how these microbes interact in the tumor and if their interactions help drive the spread of the cancer.

The second cell The study found results similar to the first, but specifically focused on gastrointestinal, lung and breast cancers. Nature reported. The researchers found that each of these three types of cancer tended to harbor the fungal genera Candida, Blastomycesand Malasseziarespectively.

Both research groups found evidence that the growth of certain fungi could be linked to poorer cancer outcomes. For example, Straussman’s group found that breast cancer patients infected with the fungus Malassezia globosa in their tumors showed poorer survival rates than patients whose tumors lacked the fungus.

The second group, led by immunologist Iliyan Iliev of Weill Cornell Medicine in New York City, found that patients with a relatively high frequency of Candida in their gastrointestinal tumors showed increased gene activity associated with rampant inflammation, cancer spread and poor survival rates, Nature reported.

Despite these early clues, none of the studies can definitively say whether fungi actually cause these poor outcomes, or whether aggressive cancers just create an environment in which these fungi can easily grow.

The studies also don’t address whether mushrooms can contribute to carcinogenesis by tricking healthy cells into becoming cancerous.

Both studies have similar limitations. For example, both pulled tissue and blood samples from existing databases, and it’s possible that some samples became contaminated with fungi during the collection process, said Ami Bhatt, a microbiome specialist at Stanford University in California Nature.

Both research groups attempted to sort out such contaminants, but even with these precautions, Bhatt said it would be best if the results could be replicated using samples taken in a sterile environment.

Straussman told STAT that these initial studies serve as a stepping stone for future research into mycobiota, the communities of microbes implicated in cancer.

“As a discipline, we need to evaluate everything we know about cancer,” he said. “Look at everything through the lens of the microbiome — the bacteria, the fungi, the tumors, even viruses. There are all these creatures in the tumor and they have to have an effect.”

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This article was originally published by Live Science. Read the original article here.