Biology subjects

Schmid, R. M.

Publications and source records attributed to Schmid, R. M..

5 recordsLinked to original sources

bioRxiv2023

Ras-dependent activation of BMAL2 regulates hypoxic metabolism in pancreatic cancer

KRAS is the archetypal oncogenic driver of pancreatic cancer. To identify new modulators of KRAS activity in human pancreatic ductal adenocarcinoma (PDAC), we performed regulatory network analysis on a large collection of expression profiles from laser capture microdissected samples of PDAC and benign controls. We discovered that BMAL2, a member of the PAS family of transcription factors, promotes tumor initiation, progression, and post-resection survival, and is highly correlated with KRAS activity. Functional analysis of BMAL2 target genes suggested a role in regulating the hypoxia response, a hallmark of PDAC. Knockout of BMAL2 in multiple human PDAC cell lines reduced cancer cell viability, invasion, and glycolysis, leading to broad dysregulation of cellular metabolism, particularly under hypoxic conditions. We find that BMAL2 directly regulates hypoxia-responsive target genes and is necessary for the stabilization of HIF1A under low oxygen conditions, while simultaneously destabilizing HIF2A. Notably, in vivo xenograft studies demonstrated that BMAL2 loss significantly impairs tumor growth and reduces tumor volume, underscoring its functional importance in tumor progression. We conclude that BMAL2 is a master transcriptional regulator of hypoxia responses in PDAC that works downstream of KRAS signaling, possibly serving as a long-sought molecular switch that distinguishes HIF1A- and HIF2A-dependent modes of hypoxic metabolism. Statement of SignificanceWe annotate the landscape of KRAS-associated transcriptional drivers of pancreatic cancer initiation, progression, and overall survival, leading to the identification of BMAL2 as a novel regulator of hypoxic metabolism. BMAL2 helps execute the oncogenic transcriptional programs of KRAS and serves as a long-sought switch between HIF1A- and HIF2A-dependent modes of hypoxic metabolism.

cancer biology↗

bioRxiv2022

Intestinal myofibroblasts regulate intestinal epithelial cell plasticity via YAP/TAZ

Intestinal stromal cells play a key role as the crypt niche cells during epithelial homeostasis and tumor initiation. However, the underlying cellular and molecular mechanisms remain unclear. We developed various types of three-dimensional (3D) tissue culture models to culture small intestinal myofibroblasts (SI MFs) together with enteroids. SI MFs significantly enhanced self-renewal, lumen formation and survival of enteroids, that was mediated via a paracrine mechanism in a Wnt-independent manner. Such co-cultured enteroids resembled SI organoids derived from Apc+/1638N tumors. Microarray analysis showed upregulation of genes associated with YAP signaling in enteroids co-cultured with SI MFs, which was confirmed by protein quantification by mass spectrometry and could be correlated with findings from human colorectal tumor specimens. Mass spectrometric analysis of conditioned media and inhibitor studies pointed to a role for TGF-{beta} in the SI MF-SI epithelium cross-talk. Altogether, utilizing different 3D stroma-epithelium co-culture models, we demonstrate here that SI MFs have the potential to induce a tumor-like phenotype in the intestinal crypts via a paracrine mechanism, that involves YAP and TGF-{beta}, but not canonical Wnt signaling.

cell biology↗

bioRxiv2022

Gut microbial disruption in critically ill patients with COVID-19 associated pulmonary aspergillosis

ObjectivesCOVID-19 disease can be exacerbated by Aspergillus superinfection (CAPA). The causes of CAPA are not yet fully understood. Recently, alterations in the gut microbiome have been associated with a complicating course and increasing severity of COVID-19 disease, most likely via immunological mechanisms. Aim of this study was to investigate a potential association between severe CAPA and alterations in the gut and bronchial microbiota. MethodsWe performed 16S rRNA gene amplicon sequencing of stool and bronchial samples from a total of 16 COVID-19 patients with CAPA and 26 patients without CAPA. All patients were admitted to the intensive care unit. Results were carefully tested for potential influences on the microbiome during hospitalization. ResultsWe found that late in COVID-19 disease, CAPA patients exhibited a trend towards reduced gut microbial diversity. Furthermore, late stage CAPA disease showed an increased presence of Staphylococcus epidermidis in the gut. This is not found in late non-CAPA cases or early disease. The analysis of bronchial samples did not show significant results. ConclusionsThis is the first study showing alterations in the gut microbiome accompany severe CAPA and possibly influence the hosts immunological response. In particular, an increase of Staphylococcus epidermidis in the intestine could be of importance. SummaryThe composition of intestinal bacteria in severe CAPA disease is altered with an increase in Staphylococcus epidermidis in the gut. Alterations in the composition of intestinal bacteria in severe CAPA may indicate immunologic involvement of the gut in the disease.

microbiology↗

bioRxiv2022

Increased glycolysis and functional mitochondria fuel acinar-ductal metaplasia in the pancreas

Reprogramming of the cellular metabolism is a hallmark of pancreatic cancer, yet it remains unclear at what stage during carcinogenesis it occurs. Here, we investigated the metabolic requirements for acinar-to-ductal metaplasia (ADM), the first step in pancreatic carcinogenesis. We detected increased glycolytic marker expression in human ADM suggesting that a metabolic switch occurs during ADM formation. We report that this switch was similarly required for ADM formation in different oncogenic mouse models (KRAS, PI3K, and MEK1) and in ligand-induced ADM in mouse wild-type acini. In addition, we show that a functional electron transport chain (ETC), but not mitochondrial ATP production, was essential to ADM formation. We conclude that the ETC provides NAD+ for the de novo synthesis of serine from glycolysis intermediates. Our findings demonstrate that metabolic programming is essential for the initiation of pancreatic carcinogenesis and thus identifies potential targets for metabolic intervention.

cancer biology↗

bioRxiv2021

Gut Bacterial Dysbiosis and Instability is Associated with the Onset of Complications and Mortality in COVID-19

ObjectiveThere is a growing debate about the involvement of the gut microbiome in COVID-19, although it is not conclusively understood whether the microbiome has an impact on COVID-19, or vice versa, especially as analysis of amplicon data in hospitalized patients requires sophisticated cohort recruitment and integration of clinical parameters. Here, we analyzed fecal and saliva samples from SARS-CoV-2 infected and post COVID-19 patients and controls considering multiple influencing factors during hospitalization. Design16S rRNA gene sequencing was performed on fecal and saliva samples from 108 COVID-19 and 22 post COVID-19 patients, 20 pneumonia controls and 26 asymptomatic controls. Patients were recruited over the first and second corona wave in Germany and detailed clinical parameters were considered. Serial samples per individual allowed intra-individual analysis. ResultsWe found the gut and oral microbiota to be altered depending on number and type of COVID-19-associated complications and disease severity. The occurrence of individual complications was correlated with low-risk (e.g., Faecalibacterium prausznitzii) and high-risk bacteria (e.g., Parabacteroides). We demonstrated that a stable gut bacterial composition was associated with a favorable disease progression. Based on gut microbial profiles, we identified a model to estimate mortality in COVID-19. ConclusionGut microbiota are associated with the occurrence of complications in COVID-19 and may thereby influencing disease severity. A stable gut microbial composition may contribute to a favorable disease progression and using bacterial signatures to estimate mortality could contribute to diagnostic approaches. Importantly, we highlight challenges in the analysis of microbial data in the context of hospitalization.

microbiology↗