Project description: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:TP53, encoding for the tumor suppressor p53, is the most frequently mutated gene in human cancer. The selective pressures shaping its mutational spectrum, dominated by missense mutations, have remained enigmatic, and neomorphic gain-of-function (GOF) activities have been implicated. We generated isogenic human leukemia cell lines of the most common TP53 missense mutations using CRISPR/Cas9. Functional, DNA binding, and transcriptional analyses revealed loss-of-function (LOF) without GOF effects of missense mutations. Comprehensive mutational scanning of p53 single amino acid variants demonstrated that DNA-binding domain missense variants exert dominant-negative effects (DNE). In mice, DNE of p53 missense variants confer a selective advantage on hematopoietic cells upon DNA damage in vivo. Clinical outcomes in acute myeloid leukemia patients showed no evidence of GOF for TP53 missense mutations. These findings establish dominant-negativity as the primary unit of selection for TP53 missense mutations in myeloid malignancies.
Project description:TP53, encoding for the tumor suppressor p53, is the most frequently mutated gene in human cancer. The selective pressures shaping its mutational spectrum, dominated by missense mutations, have remained enigmatic, and neomorphic gain-of-function (GOF) activities have been implicated. We generated isogenic human leukemia cell lines of the most common TP53 missense mutations using CRISPR/Cas9. Functional, DNA binding, and transcriptional analyses revealed loss-of-function (LOF) without GOF effects of missense mutations. Comprehensive mutational scanning of p53 single amino acid variants demonstrated that DNA-binding domain missense variants exert dominant-negative effects (DNE). In mice, DNE of p53 missense variants confer a selective advantage on hematopoietic cells upon DNA damage in vivo. Clinical outcomes in acute myeloid leukemia patients showed no evidence of GOF for TP53 missense mutations. These findings establish dominant-negativity as the primary unit of selection for TP53 missense mutations in myeloid malignancies.
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.
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.
Project description:TP53 (p53) is the most commonly mutated gene in human cancers, and p53 missense mutations are present in more than 40% of all human tumors. Most p53 mutations are located within the DNA binding domain, including hotspot mutations R175H, R248W, and R273H. To elucidate the precise mechanism by which p53 missense mutants execute their gain-of-functions (GOFs) in vivo, we used a proteomic screen to identify any protein that recognizes the p53 DNA-binding domain (DBD) in a manner dependent on its mutation status. To do so, we first purified the potential binding proteins associated with the p53 DBD through multi-step affinity chromatography from a SFB-p53 H1299 stable cell line. The affinity-purified SFB-p53 interacting proteins were detected by liquid chromatography mass spectrometry/mass spectrometry (LC–MS/MS) and revealed a few cellular proteins that have been reported to interact with the DNA binding domain of p53, such as TP53BP1, USP28, and Sirt1. Interestingly, we also identified many new interacting proteins from the same complex.
Project description:The phenotypic and transcriptomic data on ten normal breast epithelial cell lines each expressing a distinct missense mutant p53 protein, and their systems-level analysis through ChIP-Seq and RNA-seq defines the molecular basis for phenotypic heterogeneity imparted by the different missense mutant p53 proteins. The focus of the study is to gain mechanistic insight on the neomorphic function of mutant p53 proteins and their manifestation into phenotypic heterogeneity in the context of a TNBC model.