Pancreatic ductal adenocarcinoma (PDAC) is expected to be the second most deadly cancer by 2040, owing to the high incidence of metastatic disease and limited responses to treatment1,2. Less than half of all patients respond to the primary treatment for PDAC, chemotherapy3,4, and genetic alterations alone cannot explain this5. Diet is an environmental factor that can influence the response to therapies, but its role in PDAC is unclear. Here, using shotgun metagenomic sequencing and metabolomic screening, we show that the microbiota-derived tryptophan metabolite indole-3-acetic acid (3-IAA) is enriched in patients who respond to treatment. Faecal microbiota transplantation, short-term dietary manipulation of tryptophan and oral 3-IAA administration increase the efficacy of chemotherapy in humanized gnotobiotic mouse models of PDAC. Using a combination of loss- and gain-of-function experiments, we show that the efficacy of 3-IAA and chemotherapy is licensed by neutrophil-derived myeloperoxidase. Myeloperoxidase oxidizes 3-IAA, which in combination with chemotherapy induces a downregulation of the reactive oxygen species (ROS)-degrading enzymes glutathione peroxidase 3 and glutathione peroxidase 7. All of this results in the accumulation of ROS and the downregulation of autophagy in cancer cells, which compromises their metabolic fitness and, ultimately, their proliferation. In humans, we observed a significant correlation between the levels of 3-IAA and the efficacy of therapy in two independent PDAC cohorts. In summary, we identify a microbiota-derived metabolite that has clinical implications in the treatment of PDAC, and provide a motivation for considering nutritional interventions during the treatment of patients with cancer.

Receptor tyrosine kinases participate in several signaling pathways through small G proteins such as Ras (rat sarcoma). An important component in the activation of these G proteins is Son of sevenless (SOS), which catalyzes the nucleotide exchange on Ras. For optimal activity, a second Ras molecule acts as an allosteric activator by binding to a second Ras-binding site within SOS. This allosteric Ras-binding site is blocked by autoinhibitory domains of SOS. We have reported recently that Ras activation also requires the actin-binding proteins ezrin, radixin, and moesin. Here we report the mechanism by which ezrin modulates SOS activity and thereby Ras activation. Active ezrin enhances Ras/MAPK signaling and interacts with both SOS and Ras in vivo and in vitro. Moreover, in vitro kinetic assays with recombinant proteins show that ezrin also is important for the activity of SOS itself. Ezrin interacts with GDP-Ras and with the Dbl homology (DH)/pleckstrin homology (PH) domains of SOS, bringing GDP-Ras to the proximity of the allosteric site of SOS. These actions of ezrin are antagonized by the neurofibromatosis type 2 tumor-suppressor protein merlin. We propose an additional essential step in SOS/Ras control that is relevant for human cancer as well as all physiological processes involving Ras.ERM proteins | autoinhibition | GEF regulation T he small GTPase Ras (rat sarcoma) regulates essential cellular processes such as proliferation, motility, and differentiation. Activation of Ras by receptor tyrosine kinases (RTKs) is mediated by the guanine nucleotide-exchange factor (GEF) Son of sevenless (SOS). SOS is recruited by activated RTKs and subsequently engages Ras. In recent years, however, it has been recognized that this simple activation process is subject to a complex regulation. A number of regulatory motifs on SOS have been identified: the C-terminal catalytic Ras-binding domain for nucleotide exchange (1), the N-terminal half that carries histone-like sequences rich in positively charged amino acids, a Dbl homology (DH) domain, and a pleckstrin homology (PH) domain (1, 2). The DH/PH domains decrease the catalytic activity of SOS by folding back on the catalytic domain, thereby restricting accessibility to a second Ras-binding site that is distinct from the catalytic site (2). This allosteric Ras-binding site is important for the activation of SOS. Thus, Ras itself is an essential determinant of SOS regulation (2). Finally, lipid interaction contributes to the activation of SOS: The positively charged histonelike sequences interact with the negatively charged plasma membrane (3, 4). Moreover, binding of both phosphoinositides to the PH domain (5) and phosphatidic acid (PA) to the histone-like domain enhances SOS activity by relieving autoinhibition and exposing the allosteric Ras-binding site (6-8).Our interest in small GTPases was triggered originally by the observation that members of a family of actin-binding proteinsezrin, radixin, and moesin (ERM)-appear to enhance Ras activity (9). We showed that in re...

No abstract

No abstract

No abstract

The outcome of tumor treatment via hyperthermia in the clinic has been reported to be heterogeneous. Here, we assessed how the presence of gastrin-releasing peptide receptor (GRPR) and αvβ3 integrin together with the morphology of the vascularization reflects the growth behavior of tumors after hyperthermia treatment. MDA-MB-231 tumor bearing mice were treated either with high (46 °C) or low dose (42 °C) water hyperthermia for 60 min. Changes of GRPR and αvβ3 integrin expression were assessed via multiplexed optical imaging. Vascularization was reconstructed and quantified by µCT imaging after contrast agent injection. We found that high dose hyperthermia is capable of increasing the expression of GRPR, αvβ3 integrin, CD31, and Ki67 in tumors. Also the morphology of tumor vasculature changed (increased relative blood volume and small-diameter vessel density, decreased expression of α-SMA). Low dose hyperthermia induced comparatively moderate effects on the investigated protein expression pattern and vascular remodeling. We conclude that under defined circumstances, specific temperature doses affect the reorganization of tumor regrowth, which is triggered by residual “dormant” cells even though tumor volumes are transiently decreasing. Further on, GRPR, αvβ3 integrin expression are versatile tools to surveil potential tumor regrow during therapy, beyond the conventional determination of tumor volumes.

No abstract

The self‐assembly of short peptides into catalytic amyloid‐like nanomaterials has proven to be a powerful tool in both understanding the evolution of early proteins and identifying new catalysts for practically useful chemical reactions. Here we demonstrate that both parallel and antiparallel arrangements of β‐sheets can accommodate metal ions in catalytically productive coordination environments. Moreover, synergistic relationships, identified in catalytic amyloid mixtures, can be captured in macrocyclic and sheet‐loop‐sheet species, that offer faster rates of assembly and provide more complex asymmetric arrangements of functional groups, thus paving the way for future designs of amyloid‐like catalytic proteins. Our findings show how initial catalytic activity in amyloid assemblies can be propagated and improved in more‐complex molecules, providing another link in a complex evolutionary chain between short, potentially abiotically produced peptides and modern‐day enzymes.