The Epithelial To Mesenchymal Transition In Breast Cancer Induces Alterations In Metabolism

Metastasis is currently incurable. Recent studies suggest that metabolic reprogramming significantly impacts metastatic progression. Understanding the underlying biology of how metabolic reprogramming influences metastasis will shed light on developing novel ways to treat metastasis and is of urgent clinical need. A potent mediator of metastatic potential in breast cancer is the winged helix/Forkhead domain transcription factor FOXC2. We have previously shown that FOXC2 is necessary and sufficient to promote metastasis through induction of the epithelial to mesenchymal transition (EMT). EMT is a latent embryonic program that is aberrantly induced in breast cancer cells conferring migratory and invasive capabilities in addition to cancer stem cell (CSC) properties. In normal adipose tissue, FOXC2 regulates adipocyte metabolism by promoting the expression of genes associated with energy turnover, insulin sensitivity, differentiation, and mitochondrial biogenesis. I hypothesized that similar to its regulatory role of adipocyte metabolism, FOXC2 dictates metabolic functions during EMT. Here we report that distinct metabolic alterations occur with the onset of EMT. We identified an EMT metabolite signature (EMS) composed of four elevated metabolites (glutamine, glutamate, beta-alanine, and glycyleucine) and found that the EMS is predictive of poor clinical outcome in breast cancer patients. In efforts to characterize the functional relevance of the metabolic alterations defined by the EMS, we examined genes associated with metabolism that change with the onset of EMT. From this analysis, we identified genes associated with purine nucleotide and glutamine metabolism that became downregulated with the onset of EMT. We measured the expression of these genes in EMT-induced cells with FOXC2 knockdown. We observed that depletion of FOXC2 resulted in upregulation of these purine and glutamine metabolism genes and a restoration of their associated metabolism. Moreover, we found that the induction of EMT results in reduced mitochondrial metabolism and glutamine independence. This metabolic program is maintained by the downregulation of Glutaminase 2 (GLS2) expression, an enzyme that catalyzes the conversion of glutamine to glutamate. We also observed that GLS2 expression is FOXC2 dependent. Inhibition of FOXC2 signaling by treatment of cells with a small moleculae inhibitor of its upstream regulator p38MAPK with a chemical inhibitor enhanced GLS2 mRNA expression and mitochondrial metabolism. Moreover, we demonstrate that GLS2 over-expression alone increases mitochondrial metabolism, reduces the glycolytic metabolic program, and CSC mammosphere formation. Collectively these data are in line with an analysis of patient data that demonstrated that higher GLS2 expression is associated with better over-all survival. Lastly, we tested a novel therapeutic strategy that combined a p38MAPK inhibitor, which inhibits the FOXC2 signaling pathway, with a standard-of-care chemotherapeutic to reduce the tumor bulk. We observed both a decrease in lung metastasis and tumor size in mice treated with the combination strategy compared to mice receiving monotherapy

Distinguishing mechanisms underlying EMT tristability

Abstract Background The Epithelial-Mesenchymal Transition (EMT) endows epithelial-looking cells with enhanced migratory ability during embryonic development and tissue repair. EMT can also be co-opted by cancer cells to acquire metastatic potential and drug-resistance. Recent research has argued that epithelial (E) cells can undergo either a partial EMT to attain a hybrid epithelial/mesenchymal (E/M) phenotype that typically displays collective migration, or a complete EMT to adopt a mesenchymal (M) phenotype that shows individual migration. The core EMT regulatory network - miR-34/SNAIL/miR-200/ZEB1 - has been identified by various studies, but how this network regulates the transitions among the E, E/M, and M phenotypes remains controversial. Two major mathematical models – ternary chimera switch (TCS) and cascading bistable switches (CBS) - that both focus on the miR-34/SNAIL/miR-200/ZEB1 network, have been proposed to elucidate the EMT dynamics, but a detailed analysis of how well either or both of these two models can capture recent experimental observations about EMT dynamics remains to be done. Results Here, via an integrated experimental and theoretical approach, we first show that both these two models can be used to understand the two-step transition of EMT - E→E/M→M, the different responses of SNAIL and ZEB1 to exogenous TGF-β and the irreversibility of complete EMT. Next, we present new experimental results that tend to discriminate between these two models. We show that ZEB1 is present at intermediate levels in the hybrid E/M H1975 cells, and that in HMLE cells, overexpression of SNAIL is not sufficient to initiate EMT in the absence of ZEB1 and FOXC2. Conclusions These experimental results argue in favor of the TCS model proposing that miR-200/ZEB1 behaves as a three-way decision-making switch enabling transitions among the E, hybrid E/M and M phenotypes

The Epithelial to Mesenchymal Transition Promotes Glutamine Independence by Suppressing GLS2 Expression

Identifying bioenergetics that facilitate the epithelial to mesenchymal transition (EMT) in breast cancer cells may uncover targets to treat incurable metastatic disease. Metastasis is the number one cause of cancer-related deaths; therefore, it is urgent to identify new treatment strategies to prevent the initiation of metastasis. To characterize the bioenergetics of EMT, we compared metabolic activities and gene expression in cells induced to differentiate into the mesenchymal state with their epithelial counterparts. We found that levels of GLS2, which encodes a glutaminase, are inversely associated with EMT. GLS2 down-regulation was correlated with reduced mitochondrial activity and glutamine independence even in low-glucose conditions. Restoration of GLS2 expression in GLS2-negative breast cancer cells rescued mitochondrial activity, enhanced glutamine utilization, and inhibited stem-cell properties. Additionally, inhibition of expression of the transcription factor FOXC2, a critical regulator of EMT in GLS2-negative cells, restored GLS2 expression and glutamine utilization. Furthermore, in breast cancer patients, high GLS2 expression is associated with improved survival. These findings suggest that epithelial cancer cells rely on glutamine and that cells induced to undergo EMT become glutamine independent. Moreover, the inhibition of EMT leads to a GLS2-directed metabolic shift in mesenchymal cancer cells, which may make these cells susceptible to chemotherapies

CovS Simultaneously Activates and Inhibits the CovR-Mediated Repression of Distinct Subsets of Group A Streptococcus Virulence Factor-Encoding Genes▿ †

To colonize and cause disease at distinct anatomical sites, bacterial pathogens must tailor gene expression in a microenvironment-specific manner. The molecular mechanisms that control the ability of the human bacterial pathogen group A Streptococcus (GAS) to transition between infection sites have yet to be fully elucidated. A key regulator of GAS virulence gene expression is the CovR-CovS two-component regulatory system (also known as CsrR-CsrS). covR and covS mutant strains arise spontaneously during invasive infections and, in in vivo models of infection, rapidly become dominant. Here, we compared wild-type GAS with covR, covS, and covRS isogenic mutant strains to investigate the heterogeneity in the types of natural mutations that occur in covR and covS and the phenotypic consequences of covR or covS mutation. We found that the response regulator CovR retains some regulatory function in the absence of CovS and that CovS modulates CovR to significantly enhance repression of one group of genes (e.g., the speA, hasA, and ska genes) while it reduces repression of a second group of genes (e.g., the speB, grab, and spd3 genes). We also found that different in vivo-induced covR mutations can lead to strikingly different transcriptomes. While covS mutant strains show increased virulence in several invasive models of infection, we determined that these mutants are significantly outcompeted by wild-type GAS during growth in human saliva, an ex vivo model of upper respiratory tract infection. We propose that CovS-mediated regulation of CovR activity plays an important role in the ability of GAS to cycle between pharyngeal and invasive infections

The Epithelial to Mesenchymal Transition Promotes Glutamine Independence by Suppressing GLS2 Expression.

Identifying bioenergetics that facilitate the epithelial to mesenchymal transition (EMT) in breast cancer cells may uncover targets to treat incurable metastatic disease. Metastasis is the number one cause of cancer-related deaths; therefore, it is urgent to identify new treatment strategies to prevent the initiation of metastasis. To characterize the bioenergetics of EMT, we compared metabolic activities and gene expression in cells induced to differentiate into the mesenchymal state with their epithelial counterparts. We found that levels of GLS2, which encodes a glutaminase, are inversely associated with EMT. GLS2 down-regulation was correlated with reduced mitochondrial activity and glutamine independence even in low-glucose conditions. Restoration of GLS2 expression in GLS2-negative breast cancer cells rescued mitochondrial activity, enhanced glutamine utilization, and inhibited stem-cell properties. Additionally, inhibition of expression of the transcription factor FOXC2, a critical regulator of EMT in GLS2-negative cells, restored GLS2 expression and glutamine utilization. Furthermore, in breast cancer patients, high GLS2 expression is associated with improved survival. These findings suggest that epithelial cancer cells rely on glutamine and that cells induced to undergo EMT become glutamine independent. Moreover, the inhibition of EMT leads to a GLS2-directed metabolic shift in mesenchymal cancer cells, which may make these cells susceptible to chemotherapies

The risk of COVID-19 death is much greater and age dependent with type I IFN autoantibodies

International audienceSignificance There is growing evidence that preexisting autoantibodies neutralizing type I interferons (IFNs) are strong determinants of life-threatening COVID-19 pneumonia. It is important to estimate their quantitative impact on COVID-19 mortality upon SARS-CoV-2 infection, by age and sex, as both the prevalence of these autoantibodies and the risk of COVID-19 death increase with age and are higher in men. Using an unvaccinated sample of 1,261 deceased patients and 34,159 individuals from the general population, we found that autoantibodies against type I IFNs strongly increased the SARS-CoV-2 infection fatality rate at all ages, in both men and women. Autoantibodies against type I IFNs are strong and common predictors of life-threatening COVID-19. Testing for these autoantibodies should be considered in the general population

The risk of COVID-19 death is much greater and age dependent with type I IFN autoantibodies

International audienceSignificance There is growing evidence that preexisting autoantibodies neutralizing type I interferons (IFNs) are strong determinants of life-threatening COVID-19 pneumonia. It is important to estimate their quantitative impact on COVID-19 mortality upon SARS-CoV-2 infection, by age and sex, as both the prevalence of these autoantibodies and the risk of COVID-19 death increase with age and are higher in men. Using an unvaccinated sample of 1,261 deceased patients and 34,159 individuals from the general population, we found that autoantibodies against type I IFNs strongly increased the SARS-CoV-2 infection fatality rate at all ages, in both men and women. Autoantibodies against type I IFNs are strong and common predictors of life-threatening COVID-19. Testing for these autoantibodies should be considered in the general population