Project description:In obesity, sustained adipose tissue (AT) inflammation constitutes a cellular memory that limits the effectiveness of weight loss interventions. Yet, its fasting regimen-dependent regulation is unknown. Here, we show that cyclic intermittent fasting (IF) exacerbates the lipid-associated macrophage (LAM) inflammatory phenotype of visceral AT in obese mice. Importantly, we provide evidence that this increase in LAM abundance is almost entirely dependent on p53-driven adipocyte apoptosis. Adipocyte-specific deletion of p53 prevents LAM accumulation in AT during IF and increases the catabolic state of adipocytes, ameliorates metabolic flexibility, and insulin sensitivity. Finally, in cohorts of obese/diabetic patients, we describe a p53 polymorphism that links to long-term efficacy of a fasting-mimicking diet and that the expression of LAM markers and p53 in AT negatively correlates with maintaining weight loss after bariatric surgery. Overall, our results demonstrate that p53 signaling in adipocytes dictates LAM accumulation in AT under IF and that adipocyte p53 modulates fasting effectiveness in mice and humans.
Project description:In obesity, sustained adipose tissue (AT) inflammation constitutes a cellular memory that limits the effectiveness of weight loss interventions. Yet, its fasting regimen-dependent regulation is unknown. Here, we show that cyclic intermittent fasting (IF) exacerbates the lipid-associated macrophage (LAM) inflammatory phenotype of visceral AT in obese mice. Importantly, we provide evidence that this increase in LAM abundance is almost entirely dependent on p53-driven adipocyte apoptosis. Adipocyte-specific deletion of p53 prevents LAM accumulation in AT during IF and increases the catabolic state of adipocytes, ameliorates metabolic flexibility, and insulin sensitivity. Finally, in cohorts of obese/diabetic patients, we describe a p53 polymorphism that links to long-term efficacy of a fasting-mimicking diet and that the expression of LAM markers and p53 in AT negatively correlates with maintaining weight loss after bariatric surgery. Overall, our results demonstrate that p53 signaling in adipocytes dictates LAM accumulation in AT under IF and that adipocyte p53 modulates fasting effectiveness in mice and humans.
Project description:Background and Aims: p53 can limit the self-renewal of stem cells from various tissues. Experimental evidence suggests that deletion of p53 can cooperate with other oncogenic events to induce aberrant self-renewal and transformation of progenitor cells. It is not known whether p53 deletion alone can lead to liver tumor formation. Methods: We used AlfpCre mice for liver-specific deletion of Trp53 in a conditional knockout mouse model to analyze liver carcinogenesis. Results: Here, we show that liver-specific deletion of p53 in mice consistently induces formation of liver carcinoma depicting bilineal differentiation. Freshly isolated p53-/- liver progenitor cells and hepatocytes exhibit chromosomal imbalances and an enhanced clonogenic capacity compared to p53-positive cells or p21-deficient cells. Primary cultures of hepatocytes and liver progenitor cells from p53-/- mice formed tumors with bilineal differentiation when transplanted into immuno-compromised mice. Together, these results indicate that loss of p53 alone is sufficient to induce primary liver cancer with bilineal differentiation originating from chromosomal instable cultured liver progenitor cells or hepatocytes. Conclusions: The study shows that p53-dependent checkpoints inhibit transformation of liver progenitor cells and hepatocytes involving p21-independent mechanisms. Liver tumors derived from Trp53 KO mice, liver tumors from DEN-treated wildtype mice, Trp53 KO liver and wildtype liver were isolated and RNA was extracted. Agilent-026655 Mouse 4x44K v2 arrays were used.
Project description:Background and Aims: p53 can limit the self-renewal of stem cells from various tissues. Experimental evidence suggests that deletion of p53 can cooperate with other oncogenic events to induce aberrant self-renewal and transformation of progenitor cells. It is not known whether p53 deletion alone can lead to liver tumor formation. Methods: We used AlfpCre mice for liver-specific deletion of Trp53 in a conditional knockout mouse model to analyze liver carcinogenesis. Results: Here, we show that liver-specific deletion of p53 in mice consistently induces formation of liver carcinoma depicting bilineal differentiation. Freshly isolated p53-/- liver progenitor cells and hepatocytes exhibit chromosomal imbalances and an enhanced clonogenic capacity compared to p53-positive cells or p21-deficient cells. Primary cultures of hepatocytes and liver progenitor cells from p53-/- mice formed tumors with bilineal differentiation when transplanted into immuno-compromised mice. Together, these results indicate that loss of p53 alone is sufficient to induce primary liver cancer with bilineal differentiation originating from chromosomal instable cultured liver progenitor cells or hepatocytes. Conclusions: The study shows that p53-dependent checkpoints inhibit transformation of liver progenitor cells and hepatocytes involving p21-independent mechanisms.
Project description:The specific roles of mutant p53’s dominant-negative (DN) or gain-of-function (GOF) properties in regulating acute response and long-term tumorigenesis is unclear. Using “knock-in” mouse strains expressing varying R246S mutant levels, we show that DN effect on transactivation is universally observed after acute p53 activation whereas the effect on cellular outcome is cell-type specific. Reducing mutant p53 levels abrogated the DN effect. Mutant p53’s DN effect protected against radiation-induced death, but did not accentuate tumorigenesis. Furthermore, the R246S mutant did not promote tumorigenesis compared to p53-/- mice in various models, even in the absence of MDM2, unlike the R172H mutant. Together, these data demonstrate that mutant p53’s DN property only affects acute responses, whereas GOF is not universal, being mutation-type specific. Transcriptomes of 10 normal thymi harvested from 4-5 weeks old mice of different p53 and mdm2 genotype were profiled. Data was analysed by mixed model ANOVA using Partek.
Project description:Highly rearranged and mutated cancer genomes present major challenges in the identification of pathogenetic events driving the cancer process. Here, we engineered lymphoma-prone mice with chromosomal instability to assess the utility of mouse models in cancer gene discovery and the extent of cross-species overlap in cancer-associated copy number aberrations. Integrating with targeted re-sequencing, our comparative oncogenomic studies efficiently identified FBXW7 and PTEN as commonly deleted or mutated tumor suppressors in human T-cell acute lymphoblastic leukemia/lymphoma (T-ALL). More generally, the murine cancers acquire widespread recurrent clonal amplifications and deletions targeting loci syntenic to alterations present in not only human T-ALL but also diverse tumors of hematopoietic, mesenchymal and epithelial types. These results thus support the view that murine and human tumors experience common biological processes driven by orthologous genetic events as they evolve towards a malignant phenotype. The highly concordant nature of genomic events encourages the use of genome unstable murine cancer models in the discovery of biologically relevant driver events in human cancer. Experiment Overall Design: 18 lymphoma samples from Atm-/-, mTerc-/-, p53-/- triple knock-out mice were analyzed. 3 week old hymus RNA from healthy mice of p53 Hets was used as reference. Each sample was hybridized with dye-swap replica.
Project description:Unlike other EBV-associated human tumors, nearly 100% wild-type p53 gene is found in NPC, p53 protein is also frequently found to accumulate in NPC biopsies. However, the role of p53 in EBV-positive nasopharyngeal carcinoma is unclear. The expression profiles of mRNAs and miRNAs of EBV-positive NPC cells are unknown. To elucidate the function of p53 in EBV-positive NPC, we used the CRISPR-Cas9 gene editing system to p53 knockout C666-1 cells with Epstein-Barr virus and performed mRNA and miRNA sequencing in p53 KO C666-1 and their control cells. Gene Ontology (GO), KEGG and STRING analyses were implemented to identify significant functions, pathways of differentially expressed mRNAs. Through comparative analysis of p53-regulated genes from EBV-positive C666-1 cells and EBV-negative HONE2 cells with p53 target genes from 16 high throughput data sets, we found that the number of target genes and KEGG pathways downregulated by p53 in EBV-positive C666-1 cells were much less than in EBV-negative HONE2 cells, but “p53 signaling pathway” and related cell cycle arrest and apoptosis genes were significantly downregulated after knockout of p53 gene in C666-1 cells. To explore the effect of p53 on cell cycle and apoptosis, we established stable p53 C666-1-KO cell lines with stable expression of exogenous p53-WT and their control cell lines. Using the established cell lines, we observed that stable expression of p53 repressed cell proliferation, increased cell apoptosis and blocked G1/S phase progression. In conclusion, our results show that the accumulated p53 protein in EBV-positive C666-1 cells still has some tumour suppressor functions such as blocking cell-cycle progression and promoting apoptosis, but the ability of p53 to downregulate gene expression is inhibited.
Project description:The specific roles of mutant p53’s dominant-negative (DN) or gain-of-function (GOF) properties in regulating acute response and long-term tumorigenesis is unclear. Using “knock-in” mouse strains expressing varying R246S mutant levels, we show that DN effect on transactivation is universally observed after acute p53 activation whereas the effect on cellular outcome is cell-type specific. Reducing mutant p53 levels abrogated the DN effect. Mutant p53’s DN effect protected against radiation-induced death, but did not accentuate tumorigenesis. Furthermore, the R246S mutant did not promote tumorigenesis compared to p53-/- mice in various models, even in the absence of MDM2, unlike the R172H mutant. Together, these data demonstrate that mutant p53’s DN property only affects acute responses, whereas GOF is not universal, being mutation-type specific. Transcriptomes of mouse embryonic fibroblasts harvested from embyros of different p53 genotypes were profiled. A total of 6 primary clones of MEFs were used and these cells were transformed with E1A/Ras. Data was analysed by mixed model ANOVA using Partek.
Project description:The specific roles of mutant p53’s dominant-negative (DN) or gain-of-function (GOF) properties in regulating acute response and long-term tumorigenesis is unclear. Using “knock-in” mouse strains expressing varying R246S mutant levels, we show that DN effect on transactivation is universally observed after acute p53 activation whereas the effect on cellular outcome is cell-type specific. Reducing mutant p53 levels abrogated the DN effect. Mutant p53’s DN effect protected against radiation-induced death, but did not accentuate tumorigenesis. Furthermore, the R246S mutant did not promote tumorigenesis compared to p53-/- mice in various models, even in the absence of MDM2, unlike the R172H mutant. Together, these data demonstrate that mutant p53’s DN property only affects acute responses, whereas GOF is not universal, being mutation-type specific. Transcriptomes of 4 samples of normal B cells and 12 Myc-induced B lymphoma cells harvested from mice of different p53 genotypes were profiled. Data was analysed by mixed model ANOVA using Partek.
Project description:The specific roles of mutant p53’s dominant-negative (DN) or gain-of-function (GOF) properties in regulating acute response and long-term tumorigenesis is unclear. Using “knock-in” mouse strains expressing varying R246S mutant levels, we show that DN effect on transactivation is universally observed after acute p53 activation whereas the effect on cellular outcome is cell-type specific. Reducing mutant p53 levels abrogated the DN effect. Mutant p53’s DN effect protected against radiation-induced death, but did not accentuate tumorigenesis. Furthermore, the R246S mutant did not promote tumorigenesis compared to p53-/- mice in various models, even in the absence of MDM2, unlike the R172H mutant. Together, these data demonstrate that mutant p53’s DN property only affects acute responses, whereas GOF is not universal, being mutation-type specific.