Bacterial dysbiosis has emerged as an accomplice to carcinogenesis in malignancies such as colon and liver cancer, and we have recently implicated the microbiome in the pathogenesis of pancreatic ductal adenocarcinoma (PDA) 1. However, the mycobiome has not been clearly implicated in tumorigenesis. We found that fungi migrate from the gut lumen to the pancreas. PDA tumors harbored a ~3000-fold increase in fungi compared to normal pancreas in both mice and humans. The composition of the PDA mycobiome was distinct from that of gut or normal pancreas based on alpha and beta diversity indices. Specifically, the fungal community infiltrating PDA tumors was markedly enriched for Malassezia in both mice and humans. Fungal ablation was tumor-protective in slowly progressive and invasive models of PDA whereas repopulation with Malassezia-but not Candida, Saccharomyces, or Aspergillus-accelerated oncogenesis. In parallel, we discovered that ligation of mannose-binding lectin (MBL), which binds fungal wall glycans to activate the complement cascade, was required for oncogenic progression whereas MBL or C3 deletion in the extra-tumoral compartment or C3aR knockdown in tumor cells were protective. Further, reprogramming of the mycobiome did not alter PDA progression in Mbl or C3 deficient mice. Collectively, our work shows that pathogenic fungi promote PDA by driving the complement cascade via MBL activation.

Summary Pancreatic ductal adenocarcinoma (PDA) is characterized by immune-tolerance and immunotherapeutic resistance. We discovered upregulation of receptor-interacting serine/threonine-protein kinase 1 (RIP1) in tumor-associated macrophages (TAMs) in PDA. To study its role in oncogenic progression, we developed a selective small molecule RIP1 inhibitor with high in vivo exposure. Targeting RIP1 reprogrammed TAMs toward an MHCIIhiTNFα+IFNγ+ immunogenic phenotype in a STAT1-dependent manner. RIP1 inhibition in TAMs resulted in cytotoxic T cell activation and T-helper cell differentiation towards a mixed Th1/Th17 phenotype, leading to tumor-immunity in mice and in organotypic models of human PDA. Targeting RIP1 synergized with PD1- and ICOS-based immunotherapies. Tumor-promoting effects of RIP1 were independent of its co-association with RIP3. Collectively, our work describes RIP1 as a checkpoint kinase governing tumor-immunity.

The stem cell transcription factor Sox2 is highly expressed in many cancers where it is thought to mark cancer stem cells (CSC). In osteosarcomas, the most common bone malignancy, high Sox2 expression marks and maintains a fraction of tumor initiating cells that show all the properties of CSC. Knock down of Sox2 expression abolishes tumorigenicity and suppresses the CSC phenotype. Here we show that, in a mouse model of osteosarcoma, osteoblast-specific Sox2 conditional knockout (CKO) causes a drastic reduction in the frequency and onset of tumors. The rare tumors detected in the Sox2 CKO animals were all Sox2 positive, indicating that they arose from cells that had escaped Sox2 deletion. Furthermore Sox2 inactivation in cultured osteosarcoma cells by CRISPR/CAS technology leads to a loss of viability and proliferation of the entire cell population. Inactivation of the YAP gene, a major Hippo Pathway effector which is a direct Sox2 target, causes similar results and YAP overexpression rescues cells from the lethality caused by Sox2 inactivation. These effects were osteosarcoma-specific, suggesting a mechanism of cell “addiction” to Sox2 initiated pathways. The requirement for Sox2 for osteosarcoma formation as well as for the survival of the tumor cells suggests that disruption of Sox2-initiated pathways could be an effective strategy for the treatment of osteosarcoma.

Adaptive responses of skeletal muscle regulate the nuclear shuttling of the sarcomeric protein Ankrd2 that can transduce different stimuli into specific adaptations by interacting with both structural and regulatory proteins. In a genome-wide expression study on Ankrd2-knockout or -overexpressing primary proliferating or differentiating myoblasts, we found an inverse correlation between Ankrd2 levels and the expression of proinflammatory genes and identified Ankrd2 as a potent repressor of inflammatory responses through direct interaction with the NF-κB repressor subunit p50. In particular, we identified Gsk3β as a novel direct target of the p50/Ankrd2 repressosome dimer and found that the recruitment of p50 by Ankrd2 is dependent on Akt2-mediated phosphorylation of Ankrd2 upon oxidative stress during myogenic differentiation. Surprisingly, the absence of Ankrd2 in slow muscle negatively affected the expression of cytokines and key calcineurin-dependent genes associated with the slow-twitch muscle program. Thus, our findings support a model in which alterations in Ankrd2 protein and phosphorylation levels modulate the balance between physiological and pathological inflammatory responses in muscle.

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