A microscopic fungus has been found to promote the growth of tumours in the pancreas.

The microbiome is the community of microorganisms that live within the human body. The microbiome composition has been indirectly linked with a number of cancers, but this is the first time that fungi from the microbiome have been shown to directly promote tumour growth.

Although it was previously thought that the pancreas was mostly devoid of microorganisms, the study demonstrated that fungi can migrate from the main gut into the pancreas. Pancreatic tumours in both human and mice showed a 3000-fold increase in the Malassezia fungi compared to healthy pancreatic tissues.

The mice with pancreatic tumours were dosed with an anti-fungal drug, which prevented the tumours from developing. When the mice were re-infected with Malassezia fungi their tumours started growing again, demonstrating that the fungus was promoting tumour growth. Other types of fungi did not re-initiate tumour growth, suggesting that the Malassezia fungi is the only species responsible for disease progression.

The researchers investigated the molecular mechanisms that could enable Malassezia to drive tumour progression. It was found that the ligation of mannose-binding lectin (MBL), could bind to the glycans present in the fungal cell walls, to activate molecular pathways that initiated tumour growth. Deletion of MBL and knockdown of the C3aR gene in tumour cells could prevent tumour growth.

Pancreatic cancer is difficult to diagnose early but measuring the fungal population could be a viable biomarker to monitor the progression of the disease. Managing the fungal population could also represent a new treatment avenue.

At the World Metastasis Summit, taking place in Boston this November, Thomas Seyfried, Professor at Boston College, will be discussing Cancer as a Mitochondrial Metabolic Disease: Implications for Novel Therapeutics