Overview
A recent Cell journal article reveals that fungi are present in 35 different cancer types, often found inside tumor and immune cells. These fungi appear in low amounts, but their presence varies depending on the cancer type. The study also highlights important interactions between fungi, bacteria, and the immune system within tumors.
Background
Previous research shows that tumors often contain a mix of microbes, including bacteria and fungi. These communities are not randomly distributed—they are shaped by the tumor microenvironment (TME), which has limited nutrients and may be affected by antibiotic use.
While fungi are known to infect cancer patients and affect immunity, they are rarely studied in cancer research. Scientists wanted to know whether fungi are a regular part of tumor microbiomes. Understanding fungal roles could uncover new ways to diagnose or treat cancer.
About the Study
Researchers analyzed fungal DNA in two large patient groups:
- The Weizmann Institute (WIS) cohort
- The Cancer Genome Atlas (TCGA)
Together, these included 17,401 samples from blood, plasma, and tissue across 35 cancer types.
Key details of the study:
- The WIS group had 1,183 tumor and normal tissue samples from cancers of the lung, breast, brain, bone, colon, ovary, pancreas, and melanoma.
- They used ITS2 amplicon sequencing and qPCR to detect and measure fungal DNA.
- The team also used machine learning (ML) and neural networks to analyze links between fungi, bacteria, immune responses, and cancer types.
- Additional comparisons were made between early-stage (Stage I) and advanced-stage (Stage IV) cancers.
Key Findings
- Fungi were present in all 35 cancer types, but their levels varied.
- The highest fungal loads were found in breast and bone cancers.
- Compared to healthy tissue, colon and lung tumors had significantly more fungi.
- Most fungi were found inside cells, similar to intratumoral bacteria.
Although fungi were widespread, they were less diverse and abundant than bacteria. Four of seven shared cancer types between the two cohorts showed strong links between fungal and bacterial richness.
Despite low fungal numbers, several species showed interesting patterns:
- Malassezia globosa was tied to pancreatic cancer development.
- Fungal levels correlated with patient age, tumor subtype, and immunotherapy response.
The study also introduced the idea of “mycotypes”—clusters of fungi that shape tumor environments:
- F1: Malassezia, Ramularia, Trichosporon
- F2: Aspergillus, Candida
- F3: Multiple genera, including Yarrowia
These clusters were tied to specific immune responses and helped separate patients by survival outcomes and therapy success.
Immune and Microbial Interactions
Tumors don’t seem to be competitive environments for microbes like the gut is. Instead, they may allow multiple microbes to live side-by-side—a “permissive phenotype.”
The fungi interacted with bacteria and immune cells in cancer-type-specific ways. For example, breast cancer had strong co-occurrences between fungi and bacteria—up to 96.5%—with Aspergillus and Malassezia as key players.
Importantly:
- Fungal-bacterial-immune clusters could predict immune response types.
- These patterns may help identify early-stage cancers or guide treatment decisions.
- Some fungal species were clearly linked to cancer progression in the stomach, rectum, and kidneys.
Conclusions
This study offers the first detailed look at fungi in plasma samples from early-stage cancer patients. Fungi were found in 35 cancer types, often located inside immune and tumor cells.
While the source of fungi in plasma is still unknown, their consistent presence—along with their links to immune response and cancer stage—suggests fungi could become valuable cancer biomarkers.
The findings also highlight the importance of studying fungi as part of the broader tumor ecosystem, alongside bacteria and immune cells. These microbial communities could open up new diagnostic and therapeutic options in oncology.