Jake Naughton/The New York Times

Scientists have recently extended microbiome research into the field of oncology due to the presence of bacterial communities in tumors.

November 2, 2022

Research Suggests the Fungal Microbiome Provides Insight into Cancer Incidence

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On Sept. 29, the Iliev Lab at Weill Cornell Medicine published a study that links certain fungal species to specific types and severity of cancer. 

Researchers have conducted many investigations to learn more about the operation and diversity of the human microbiome. The microbiome includes bacteria, viruses, and fungi, affecting mood, food digestion and the immune system. 

The co-habitation of the microbiome facilitates an ecosystem for microbe-microbe and host-microbe interactions. These interactions can subsequently affect the health of a human host and result in cancer. 

Scientists have recently extended microbiome research into the field of oncology due to the presence of bacterial communities in tumors, which were previously thought to be sterile, or free from bacteria or living organisms. 

According to Iliev’s study, cancer-associated bacteria can affect the host immune system by causing inflammation, which contributes to their tumor-forming capabilities. Researchers have hypothesized that microbes associated with tumors might contribute to their growth by protecting them from the immune system or neutralizing drugs targeting the tumor. 

The presence of bacteria within the “tumor microbiome,” or microbes that inhabit cancerous tumors, is well known among the scientific community. However, the effects of the fungal microbiome on tumor development are not as conclusive.

Studies conducted by the Iliev Lab have identified fungal species associated with the tumor microbiome. Fungi are diverse and are found in our everyday environments. These organisms have also been found inside our bodies and although they are found in abundance, the specific characteristics and functions of certain fungi are still unknown.

In order to examine fungal presence in tumors, the Iliev Lab sequenced data from the Cancer Genome Atlas, a searchable database of DNA from various types of cancer compiled in the early 2000s. 

This project was originally created with the intention of observing which mutations in tumor genes allow for uncontrolled growth but has recently been used to observe the presence of both bacterial and fungal DNA in cancerous tumors.

Dr. Iliev and his colleagues found fungi in tumors associated with the head-neck area, as well as in the neck, lung, breasts and stomach. 

A separate study published in September, unaffiliated with Iliev’s research, observed tumors from 35 different types of cancer from the Cancer Genome Atlas, finding a unique composition of fungi in each of the 35 tumor types.

Both studies found that fungal compositions correspond to certain types of cancer as well as varying cancer stages. The Iliev Lab found that Candida species, a type of fungus responsible for yeast infections, were abundant in the GI tumor fungal microbiome, also referred to as the mycobiome. They also discovered an abundance of Blastomyces and Malassezia species in lung and breast tumors, respectively. 

Major findings of Iliev’s research include the association of Candida with gastrointestinal cancers and the ability to link reduced survival with the presence of Candida in the tumors of those with stomach cancer.

According to the Iliev study, “these results not only implicate Candida spp. in the pathogenesis of GI cancers but also indicate its potential as a therapeutic target and prognostic tool.”

Because the tumor microbiome displays specificity toward certain types of microbes, scientists hope to someday detect cancers by measuring microbial DNA in the blood and combat metastasis by targeting both a tumor and its associated microbes. 

“If you have a test, [you can] find people at risk. You can monitor them more often… In a blood sample you might get more information without having the invasive procedure…” Dr. Iliev said.

Iliev’s research notes the possibility of treating the presence of Candida DNA in the blood as a prognostic biomarker, which is a clinical or biological characteristic that provides insight into the future health of the patient. 

“It [fungal composition] can predict to some degree that there is a problem, but it cannot tell you exactly what the problem is if it is only microbial. So you have to combine that with basically other markers that are coming from either the tumor or from the immune status of the patient” Dr. Iliev said

Although this microbiome clinical research will not be available to the public for many years, the developments in this field provide researchers with a clearer understanding of the relationship between the human microbiome and cancer.