The fungal mycobiome promotes pancreatic oncogenesis via activation of MBL.

Bacterial dysbiosis accompanies carcinogenesis in malignancies such as colon and liver cancer, and has recently been implicated in the pathogenesis of pancreatic ductal adenocarcinoma (PDA)1. However, the mycobiome has not been clearly implicated in tumorigenesis. Here we show that fungi migrate from the gut lumen to the pancreas, and that this is implicated in the pathogenesis of PDA. PDA tumours in humans and mouse models of this cancer displayed an increase in fungi of about 3,000-fold compared to normal pancreatic tissue. The composition of the mycobiome of PDA tumours was distinct from that of the gut or normal pancreas on the basis of alpha- and beta-diversity indices. Specifically, the fungal community that infiltrated PDA tumours was markedly enriched for Malassezia spp. in both mice and humans. Ablation of the mycobiome was protective against tumour growth in slowly progressive and invasive models of PDA, and repopulation with a Malassezia species-but not species in the genera Candida, Saccharomyces or Aspergillus-accelerated oncogenesis. We also discovered that ligation of mannose-binding lectin (MBL), which binds to glycans of the fungal wall to activate the complement cascade, was required for oncogenic progression, whereas deletion of MBL or C3 in the extratumoral compartment-or knockdown of C3aR in tumour cells-were both protective against tumour growth. In addition, reprogramming of the mycobiome did not alter the progression of PDA in Mbl- (also known as Mbl2) or C3-deficient mice. Collectively, our work shows that pathogenic fungi promote PDA by driving the complement cascade through the activation of MBL.

Targeting Piezo1 unleashes innate immunity against cancer and infectious disease.

Piezo1 is a mechanosensitive ion channel that has gained recognition for its role in regulating diverse physiological processes. However, the influence of Piezo1 in inflammatory disease, including infection and tumor immunity, is not well studied. We postulated that Piezo1 links physical forces to immune regulation in myeloid cells. We found signal transduction via Piezo1 in myeloid cells and established this channel as the primary sensor of mechanical stress in these cells. Global inhibition of Piezo1 with a peptide inhibitor was protective against both cancer and septic shock and resulted in a diminution in suppressive myeloid cells. Moreover, deletion of Piezo1 in myeloid cells protected against cancer and increased survival in polymicrobial sepsis. Mechanistically, we show that mechanical stimulation promotes Piezo1-dependent myeloid cell expansion by suppressing the retinoblastoma gene Rb1 We further show that Piezo1-mediated silencing of Rb1 is regulated via up-regulation of histone deacetylase 2. Collectively, our work uncovers Piezo1 as a targetable immune checkpoint that drives immunosuppressive myelopoiesis in cancer and infectious disease.