Recruitment of Pontin/Reptin by E2f1 amplifies E2f transcriptional response during cancer progression

Changes in gene expression during tumorigenesis are often considered the consequence of de novo mutations occurring in the tumour. An alternative possibility is that the transcriptional response of oncogenic transcription factors evolves during tumorigenesis. Here we show that aberrant E2f activity, following inactivation of the Rb gene family in a mouse model of liver cancer, initially activates a robust gene expression programme associated with the cell cycle. Slowly accumulating E2f1 progressively recruits a Pontin/Reptin complex to open the chromatin conformation at E2f target genes and amplifies the E2f transcriptional response. This mechanism enhances the E2f-mediated transactivation of cell cycle genes and initiates the activation of low binding affinity E2f target genes that regulate non-cell-cycle functions, such as the Warburg effect. These data indicate that both the physiological and the oncogenic activities of E2f result in distinct transcriptional responses, which could be exploited to target E2f oncogenic activity for therapy

Recruitment of Pontin/Reptin by E2f1 amplifies E2f transcriptional response during cancer progression

Changes in gene expression during tumorigenesis are often considered the consequence of de novo mutations occurring in the tumour. An alternative possibility is that the transcriptional response of oncogenic transcription factors evolves during tumorigenesis. Here we show that aberrant E2f activity, following inactivation of the Rb gene family in a mouse model of liver cancer, initially activates a robust gene expression programme associated with the cell cycle. Slowly accumulating E2f1 progressively recruits a Pontin/Reptin complex to open the chromatin conformation at E2f target genes and amplifies the E2f transcriptional response. This mechanism enhances the E2f-mediated transactivation of cell cycle genes and initiates the activation of low binding affinity E2f target genes that regulate non-cell-cycle functions, such as the Warburg effect. These data indicate that both the physiological and the oncogenic activities of E2f result in distinct transcriptional responses, which could be exploited to target E2f oncogenic activity for therapy

In vivo characterization of glutamine metabolism identifies therapeutic targets in clear cell renal cell carcinoma

Targeting metabolic vulnerabilities has been proposed as a therapeutic strategy in renal cell carcinoma (RCC). Here, we analyzed the metabolism of patient-derived xenografts (tumorgrafts) from diverse subtypes of RCC. Tumorgrafts from VHL-mutant clear cell RCC (ccRCC) retained metabolic features of human ccRCC and engaged in oxidative and reductive glutamine metabolism. Genetic silencing of isocitrate dehydrogenase-1 or isocitrate dehydrogenase-2 impaired reductive labeling of tricarboxylic acid (TCA) cycle intermediates in vivo and suppressed growth of tumors generated from tumorgraft-derived cells. Glutaminase inhibition reduced the contribution of glutamine to the TCA cycle and resulted in modest suppression of tumorgraft growth. Infusions with [amide-15N]glutamine revealed persistent amidotransferase activity during glutaminase inhibition, and blocking these activities with the amidotransferase inhibitor JHU-083 also reduced tumor growth in both immunocompromised and immunocompetent mice. We conclude that ccRCC tumorgrafts catabolize glutamine via multiple pathways, perhaps explaining why it has been challenging to achieve therapeutic responses in patients by inhibiting glutaminase

Antibiotic treatment of wild type mice decreases bacterial load and does not produce overt immunological changes.

<p>(A) The average fold change in 16 s rDNA copies was quantified by qPCR from stool of wildtype mice treated with antibiotics and sucralose (n=5) or sucralose alone (n=3). Data shown is the fold change in 16S copies after 13 days of treatment. Error bars represent the SD. (B) The weight of mice treated with sucralose only (black line) or sucralose and antibiotics (dotted line) is shown over the course of treatment. Dot represents the mean of the population and error bars are the SD from the mean. (C) Percentages of activated splenic CD4+ T cells (defined as shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0034478#pone-0034478-g001" target="_blank">Figure 1D</a>) in mice treated with sucralose only or sucralose and antibiotics is shown. Each dot represents a single mouse. (D–E) Histological sections of the esophagus (D) and small bowel (E) are shown for mice treated with sucralose only (−antibiotics) or sucralose and antibiotics (+antibiotics). A 10× objective was used for esophagus and a 40× objective was used to analyze small bowel.</p

Antibiotic Treatment of Ndfip1 cKOs from Birth Does Not Reduce Inflammation.

<p>(A–D) Representative flow cytometry plots of cells isolated from the esophagus (A) and small bowel (C) of Ndfip1-cKO and control animals treated from birth to 5 weeks. Graphs of the percentages of eosinophils (Siglec F+) and CD4+ T cells in esophagus (B) or small bowel (D) from all mice in the experiment are shown. (E) Representative flow plots illustrating the percentage of activiated cells among splenic CD4+ gated T cells. (F) Percentages of activated T cells in the spleens of all mice treated with antibiotics from birth to 5 weeks are shown.</p

Ndfip1 CD4-cKO mice treated with antibiotics for 2 weeks do not show decreased eosinophilia or reduced inflammation in the esophagus.

<p>(A) The average 16s rDNA copies/nanogram of total stool DNA was quantified by qPCR at day 0 and day 13 of treatment with sucralose alone (n=5) or sucralose and antibiotics (n=4). Error bars illustrate SD. (B) Weights of mice treated with sucralose alone (−ABX=solid line) or antibiotics and sucralose (+ABX=dashed line) over the course of the 13 day treatment. (C) Representative H & E stained histological sections of the esophagus and small bowel of Ndfip1-cKO mice after 13 days of treatment with sucralose alone or antibiotics and sucralose are shown. (D) Percentages of activated CD4+ T cells in the spleens of mice treated with sucralose only (untreated) or with antibiotics and sucralose (treated) as determined by flow cytometric analysis. Each dot represents a single mouse.</p

Ndfip1 CD4-cKO mice treated with antibiotics from birth do not show changes in eosinophilia or inflammation in the esophagus, or splenic T cell activation.

<p>(A) Weights of control mice (n=4) (closed circles) or Ndfip1-cKO mice(n=4) (open circles) between weeks 3 to 5 of antibiotic treatment. (B) H & E stains of histological sections of esophagus taken from control and Ndfip1-cKO mice after antibiotic treatment from birth to 5 weeks. Images were taken using a 20× objective. Inset of panel outlined by the box is shown in the images on the right.</p

p53 Suppresses Metabolic Stress-Induced Ferroptosis in Cancer Cells

How cancer cells respond to nutrient deprivation remains poorly understood. In certain cancer cells, deprivation of cystine induces a non-apoptotic, iron-dependent form of cell death termed ferroptosis. Recent evidence suggests that ferroptosis sensitivity may be modulated by the stress-responsive transcription factor and canonical tumor suppressor protein p53. Using CRISPR/Cas9 genome editing, small-molecule probes, and high-resolution, time-lapse imaging, we find that stabilization of wild-type p53 delays the onset of ferroptosis in response to cystine deprivation. This delay requires the p53 transcriptional target CDKN1A (encoding p21) and is associated with both slower depletion of intracellular glutathione and a reduced accumulation of toxic lipid-reactive oxygen species (ROS). Thus, the p53-p21 axis may help cancer cells cope with metabolic stress induced by cystine deprivation by delaying the onset of non-apoptotic cell death

Data from: Recruitment of Pontin/Reptin by E2f1 amplifies E2f transcriptional response during cancer progression

Changes in gene expression during tumorigenesis are often considered the consequence of de novo mutations occurring in the tumor. An alternative possibility is that the transcriptional response of oncogenic transcription factors evolves during tumorigenesis. Here, we show that aberrant E2f activity, following inactivation of the Rb gene family in a mouse model of liver cancer, initially activates a robust gene expression program associated with the cell cycle. Slowly accumulating E2f1 progressively recruits a Pontin/Reptin complex to open the chromatin conformation at E2f target genes and amplifies the E2f transcriptional response. This mechanism enhances the E2f-mediated transactivation of cell cycle genes and initiates the activation of low binding affinity E2f target genes that regulate non-cell cycle functions, such as the Warburg effect. These data indicate that both the physiological and the oncogenic activities of E2f result in distinct transcriptional responses, which could be exploited to target E2f oncogenic activity for therapy

Data from: Recruitment of Pontin/Reptin by E2f1 amplifies E2f transcriptional response during cancer progression

Changes in gene expression during tumorigenesis are often considered the consequence of de novo mutations occurring in the tumor. An alternative possibility is that the transcriptional response of oncogenic transcription factors evolves during tumorigenesis. Here, we show that aberrant E2f activity, following inactivation of the Rb gene family in a mouse model of liver cancer, initially activates a robust gene expression program associated with the cell cycle. Slowly accumulating E2f1 progressively recruits a Pontin/Reptin complex to open the chromatin conformation at E2f target genes and amplifies the E2f transcriptional response. This mechanism enhances the E2f-mediated transactivation of cell cycle genes and initiates the activation of low binding affinity E2f target genes that regulate non-cell cycle functions, such as the Warburg effect. These data indicate that both the physiological and the oncogenic activities of E2f result in distinct transcriptional responses, which could be exploited to target E2f oncogenic activity for therapy