26S proteasome is conserved, therapeutically relevant mediator of mutant p53 gain-of-function in cancer
ABSTRACT: Mutant p53 proteins, resulting form frequent TP53 tumor suppressor missense mutations, possess gain-of-function activities and are among the most widespread and robust oncoproteins in human tumors. They are potentially important but understudied therapeutic targets. No studies to date have distinguished common, therapeutically relevant mutant p53 gain-of-function effects, from effects specific to different mutant variants and cell backgrounds. Here we identify 26S proteasome machinery as the common downstream effector controlled by mutant p53s in Triple Negative Breast Cancer (TNBC - aggressive carcinomas with TP53 as the most frequently mutated locus) and conserved in other human cancers. We have identified this pathway using a combination of single-model, multi-method vertical analysis (whole cell proteome, RNA sequencing an ChIP sequencing) and multi-cell line, horizontal analysis of transcriptiomes. We found that different missense mutant p53s regardless of the cell background transcriptionaly activate whole 26S proteasome machinery. Proteasome activity is significantly increased in p53 mutant versus wild-type or knockdown/null status - in cellular and mouse models as well as in human breast tumors. Increased proteasome activity leads to inhibition of tumor suppressive pathways. The control of mutant p53 over proteasome transcription and activity results in the increased resistance to proteasome inhibitors. By combining the mutant p53 targeting agents and proteasome inhibitor we were able to overcome the “bounce-back” proteasome inhibitor resistance mechanism in mutant p53 bearing TNBC cells and xenografts in vivo.
Project description:Mutant p53 proteins, resulting from the missense mutations of the TP53 tumor suppressor gene, possess gain-of-function activities and are among the most robust oncoproteins in human tumors. They are potentially important therapeutic targets. No studies to date have distinguished common, therapeutically relevant mutant p53 gain-of-function effects from effects specific to different mutant variants and cell backgrounds. here we performed RNA-seq analysisin MDA-MB-231 (R280K) upon silencing TP53 or the control siRNA. Overall design: MDA-MB-231 (R280K) cell line was transfected with control or p53 siRNA.So The study comprises one experimental cell line,in triplicate.
Project description:TP53 mutations occur in approximately 50% of all human tumors with increased frequency in aggressive cancers that are notoriously difficult to treat. Additionally, p53 missense mutations are remarkably predictive of refractoriness to chemo/radiotherapy in various malignancies. These observations have led to the development of mutant-p53 targeting agents that restore p53 function. An important unknown is which p53-mutant tumors will respond to p53 reactivation-based therapies. Here we found a heterogeneous impact on therapeutic response to p53 restoration, suggesting it will unlikely be effective as a single therapy. The goal of the study was to identify the pathways conferring resistance or sensitivity to genetic p53 restoration in tumors with a p53 missense mutaiton Results:We sequenced the transcriptome of tumors that were sensitive or resistant to p53 restoration and found that TNF signaling was activated in p53-sensitive tumors. Overall design: 12 independent biological samples were analyzed to compare tumors that were sensitive (n=8) or resistant (n=4) to genetic p53 restoration
Project description:Mutant p53 proteins, resulting from the missense mutations of the TP53 tumor suppressor gene, possess gain-of-function activities and are among the most robust oncoproteins in human tumors. They are potentially important therapeutic targets. No studies to date have distinguished common, therapeutically relevant mutant p53 gain-of-function effects from effects specific to different mutant variants and cell backgrounds. here we perform the analysis of transcriptomes,rRegardless of the cell background, of different mutant p53s. Overall design: Four different cell lines were transfected with control or p53 siRNA.So The study comprises four experimental cell lines, each in triplicate.
Project description:We investigate the roles of natively present PTMs on stability of interactions in three large and essential yeast Saccharomyces cerevisiae complexes: exosome, RNA polymerase II and 26S proteasome.
Project description:Mutant p53 proteins, resulting from the missense mutations of the TP53 tumor suppressor gene, possess gain-of-function activities and are among the most robust oncoproteins in human tumors. They are potentially important therapeutic targets. To complement our mutant p53 transcriptomic studies we have performed ChIP-seq analysis in MDA-MB-231 (R280K) using the mouse anti-p53 DO1 antibody or control mouse IgG versus the input material. Overall design: ChIP-seq analysis was performed in MDA-MB-231 (R280K) using the mouse anti-p53 DO1 antibody (Santa Cruz Biotech.) and MDA-MB-231 (R280K) with mouse unspecific IgG antibody (Santa Cruz Biotech.) as negative control.
Project description:MDA-MB-231 are a metastatic triple-negative breast cancer cell line that bears a missense p53 mutation (R280K). We depleted endogenous mutp53 in MDA-MB-231 cells by siRNA transfection, and treated the cells with Tumor Necrosis Factor (TNF)-alpha. Microarray analysis was performed to evaluate the impact of mutant p53 on the transcriptional response triggered by TNFα in these cells. MDA-MB-231 cells transfected with control or p53 siRNA were treated with TNFα for 20 hrs or left untreated. The study comprises four experimental points, each in triplicate.
Project description:The human TP53 gene is frequently mutated in tumors and cell lines. Unlike other tumor suppressors that are commonly inactivated by deletions or nonsense mutations, the majority of p53-mutations are missense point mutations that result in the expression of a full-length protein with an altered amino acid that has lost sequence specific DNA-binding. Expression of mutant p53 (mutp53) confers advantages to tumor cells and transcriptional regulation of several genes mediating the beneficial effects has been shown to play a role. However, molecular mechanisms of transcriptional regulation by mutp53 are still poorly understood. We used the glioblastoma-derived U-251 MG human cell line endogenously expressing mutp53 protein (R273H mutation) to analyze gene expression profiles on Agilent Whole Human Genome Microarray after transient and stable depletion of mutp53 expression. Gene expression data was correlated with a ChIP study on a custom tiling array to understand the contribution of endogenously expressed mutp53 to transcriptional regulation. This series of microarray experiments contains the gene expression profiles of glioblastoma-derived U-251 MG human cell lines engineered to constitutively express a p53-specific shRNA or scrambled control shRNA. To reverse the effect of mutp53 depletion, stable clones were modified by stable integration of a mutp53-R273H expression construct or empty pCDNA3 vector as a control. In addition, we performed gene expression analysis of U-251 MG cells transiently transfected with p53-specific siRNA or control siRNA (3 biological replicates each).
Project description:Study of the effects of the VCP knockdown. VCP (p97, yeast cdc48) is a hexameric AAA ATPase involved in various cellular functions including degradation of proteins by the ubiquitin-proteasome system. We examine the consequences of the reduction of VCP levels after RNAi of VCP in HeLa cells. We find ~30 transcripts upregulated in a sequence independent manner. Those transcripts encode proteins involved in endoplasmic reticulum stress, apoptosis, and amino acid starvation.
Project description:The point mutation that substitutes lysine with arginine at position 120 of human p53 has been characterized as a missense mutation. The K120R mutation renders the p53 protein disabled for acetylation and, as a result, defective for apoptotic function, which provides a mechanistic link between the missense mutation and tumorigenesis. However, we noticed the failures of tumorigenesis in mice with the mutation, and of the related studies to notice that it has arbitrarily reflected in amino acid change through a sequence modification (AGA) of the original tumor mutation (AGG) by codon degeneracy. Unlike this modified version, we also discovered a novel splicing site the original mutation, TP53 c.359A>G, may induce. Using a human induced pluripotent stem cell line that was engineered to be homozygous for the original mutation, we here identified that the accidental splicing site generates a defective transcript variant with a frame-shifted premature termination codon which is subjected to nonsense-mediated mRNA decay. The authentic splicing still occurs but in extremely low amounts. Taken together, this mutation causes depletion of cellular p53 via defective mRNA, suggesting a new link to tumorigenesis. Overall design: We generated p53 knockout cells or p53 mutated cells (TP53 c.359A>G) from human (fibroblasts cell line) induced pluripotent stem cells. Responsive patterns of gene expression by doxorubicin treatment was compared between these cells.
Project description:The Wilms tumor 1 (WT1) gene encodes a zinc finger transcription factor important for normal kidney development. WT1 is a suppressor for Wilms tumor development and an oncogene for diverse malignant tumors. We recently established cell lines from primary Wilms tumors and identified the corresponding WT1 mutations (see GSE18058). To investigate the function of mutant WT1 proteins we performed WT1 knockdown experiments in primary Wilms tumor cell lines with a frameshift/extension (p.V432fsX87 = Wilms3) and a stop mutation (p.P362X = Wilms2) of WT1, followed by genome wide gene expression analysis. A detailed analysis of these gene expression data using MetaCore enabled us to classify the WT1 mutations as gain of function mutations. The mutant WT1Wilms2 and WT1Wilms3 proteins acquired an ability to modulate the expression of a highly significant number of genes from the G2/M phase of the cell cycle, and WT1 knockdown experiments showed that they are required for Wilms tumor cell proliferation. Data from the literature show that p53 negatively regulates the activity of a large number of these genes which are also part of a core proliferation cluster in diverse human cancers. Our data strongly suggest that mutant WT1 proteins facilitate expression of these cell cycle genes by antagonizing transcriptional repression mediated by p53. In light of this it is important to note that mutant WT1 has an ability to physically interact with the tumor suppressor p53. Together the findings show for the first time, that mutant WT1 proteins have a gain of function and act as oncogenes for Wilms tumor development by regulating Wilms tumor cell proliferation. siWT1 mediated knockdown in two Wilms tumor cell lines one and two days after transfection versus non-silencing controls