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.
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The sequence datasets analysed in this article are publicly available in the NCBI BioProject database, under the accession number PRJNA557226. Raw data for all experiments are available as Source Data to the relevant figures. Any other relevant data are available from the corresponding authors upon reasonable request.
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We acknowledge the use of the Experimental Pathology and Microscopy core facilities at NYU School of Medicine. These shared resources are partially supported by the Cancer Center Support Grant, P30CA016087, at the Laura and Isaac Perlmutter Cancer Center. This work was supported by NIH grants CA168611 (G.M.), CA206105 (G.M. and D.S.), CA215471 (G.M.), CA19311 (G.M.), DK106025 (G.M.), DE025992 (D.S. and X.L.) and UL1TR001445 (J.I.K.), Department of Defense grant CA170450 (G.M.) and Deutsche Forschungsgemeinschaft Grant AY 126/1-1 (B.A.).
The authors declare no competing interests.
Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Peer review information Nature thanks Marina Pasca di Magliano and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.
Extended data figures and tables
Fungal DNA content was tested using qPCR in pancreata from control (ctl) mice (n = 5) and mice induced to develop caerulein-induced pancreatitis (n = 5). ns, not significant. Data are mean ± s.e.m. Two-tailed Student’s t-test. Source data
Hierarchical tree cladogram depicting changes in the taxonomic composition of the mycobiome (assigned to the genus level) in the guts of 30-week-old KC (n = 14) compared to wild-type (n = 12) mice, based on the average percentage relative abundance of genera as determined by 18S ITS sequencing. Source data
a, Wild-type mice that bear orthotopic PDA tumours were treated with vehicle (n = 7 mice) or fluconazole (n = 8 mice), and killed three weeks later. Tumours were collected and weighed. Data are representative of experiments that were performed twice. Scale bar, 1 cm. b, Germ-free wild-type mice were treated with amphotericin B (n = 6 mice) or vehicle (n = 10 mice), and orthotopic tumours from KPC mice were administered to them. Mice were killed three weeks later, and tumours were collected and weighed. Scale bar, 1 cm. c–e, Wild-type mice induced to develop caerulein-induced pancreatitis were serially treated with amphotericin B (n = 5 mice) or vehicle (n = 3 mice). c, Representative H&E-stained sections of pancreata are shown, and pancreatic oedema was quantified by measuring the percentage of the area that was white space. Scale bar, 100 μm. d, CD45+ inflammatory cell infiltration was determined by immunohistochemistry. Scale bar, 20 μm. e, Serum levels of amylase were measured. n = 5 mice treated with amphotericin B, n = 3 mice treated with vehicle and n = 3 mock-treated (control) mice. f, Wild-type mice treated with amphotericin B were repopulated with C. tropicalis (n = 4 mice) or vehicle (n = 4 mice), and killed three weeks later. Tumours were collected and weighed. Scale bar, 1 cm. Data are mean ± s.e.m. P values determined by two-tailed Student’s t-test (a–f). Source data
a, Kaplan–Meier survival curve of patients with PDA, stratified by high (n = 16 patients), medium-high (n = 24 patients), medium-low (n = 26 patients) and low (n = 17 patients) expression of MBL on the basis of data from TCGA. b, Orthotopic tumours from KPC mice were administered to MBL-null mice treated with vehicle (n = 3 mice) or amphotericin B (n = 4 mice), and killed three weeks later. Tumours were collected and weighed. Data are representative of three separate experiments. c, MBL-null mice treated with amphotericin B were repopulated with M. globosa (n = 5 mice) or sham-repopulated (n = 4 mice), and killed three weeks later. Tumours were collected and weighed. Data are representative of experiments that were repeated twice. d, Kaplan–Meier survival curve of patients with PDA, stratified by high (n = 18) versus low (n = 15) expression of C3, on the basis of data from TCGA. e, Pancreata from three-month-old wild-type, KC and KC, MBL-null mice were stained using a monoclonal antibody against C3a. Representative images from two experiments are shown. Scale bar, 20 μm. f, KPC tumour cells were seeded in 96-well plates with vehicle or recombinant mouse C3a. n = 5 cells per group for each time point. Cellular proliferation was measured at serial time points using the XTT assay. Data are representative of experiments that were repeated three times. Data are mean ± s.e.m. P values determined by two-tailed log-rank test (a, d) or two-tailed Student’s t-test (b, c, f). Source data
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Nature Reviews Cancer (2019)