Project description:TP53 R175H mutation is one of the most common mutations in human cancers and cancer cells with this mutation stably express R175H protein in the nucleus. To identify the synthetic lethal gene interacted with the R175H, we conducted the high throughput screening by using tetracyclin inducible R175H expression system in SF126 cells and comprehensive shRNA library carried by lenti virus. We identified 906 candidate gene suppressions that may lead to accelerated cell growth inhibition under the presence of R175H. Inhibitor of differentiation 1 (ID1) was one of the candidate genes and suppression of ID1 by siRNA resulted in acceleration of growth inhibition of cell lines expressing endogenous R175H but not in TP53 null cell lines. The transient expression of R175H in TP53 null cell lines and suppression of ID1 and/or TP53 R175H in cell lines with endogenous R175H revealed that the cell growth inhibition by ID1 suppression was dependent on R175H expression but not other common p53 mutants (R273H). Flow cytometric (FACS) analysis exhibited that ID1 suppression resulted in G1 arrest and the arrest was accelerated by suppression of R175H. In conclusion, ID1 is a synthetic lethal gene interacted with R175H and is considered to be a novel molecular target of cancer therapy for R175H expressing cells. R175H expression(Tet-on) group was labeled by Cy5, and p53-null(Tet-off) group was labeled by Cy3. Three independent experiments were conducted (We have triplicate data).
Project description:TP53 R175H mutation is one of the most common mutations in human cancers and cancer cells with this mutation stably express R175H protein in the nucleus. To identify the synthetic lethal gene interacted with the R175H, we conducted the high throughput screening by using tetracyclin inducible R175H expression system in SF126 cells and comprehensive shRNA library carried by lenti virus. We identified 906 candidate gene suppressions that may lead to accelerated cell growth inhibition under the presence of R175H. Inhibitor of differentiation 1 (ID1) was one of the candidate genes and suppression of ID1 by siRNA resulted in acceleration of growth inhibition of cell lines expressing endogenous R175H but not in TP53 null cell lines. The transient expression of R175H in TP53 null cell lines and suppression of ID1 and/or TP53 R175H in cell lines with endogenous R175H revealed that the cell growth inhibition by ID1 suppression was dependent on R175H expression but not other common p53 mutants (R273H). Flow cytometric (FACS) analysis exhibited that ID1 suppression resulted in G1 arrest and the arrest was accelerated by suppression of R175H. In conclusion, ID1 is a synthetic lethal gene interacted with R175H and is considered to be a novel molecular target of cancer therapy for R175H expressing cells.
Project description:Gain-of-function p53 mutants such as p53-R175H form stable aggregates that accumulate in cells and play an important role in cancer progression. Selective degradation of gain-of-function p53 mutants has emerged as a highly attractive therapeutic strategy to target cancer cells harboring specific p53 mutations. We identified a small molecule called MCB-613 to cause rapid ubiquitination, nuclear export, and degradation of p53-R175H through lysosome-mediated pathway leading to catastrophic cancer cell death. In contrast to its effect on the p53-R175H mutant, MCB-613 causes slight stabilization of p53-WT and has weaker effects on other p53 gain-of-function mutants. Using state-of-the-art genetic and chemical approaches, we identified the deubiquitinase USP15 as the mediator of MCB-613’s effect on p53-R175H and established USP15 as a selective upstream regulator of p53-R175H in ovarian cancer cells. These results confirm that distinct pathways regulate the turnover of p53-WT and the different p53 mutants and open new opportunities to selectively target them.
Project description:LMSU gastric cancer cells were manipulated to either knockout or knockdown mutant p53-R175H, which is endogenously mutated and expressed in this cell line.
Project description:Mutations in the p53 tumor suppressor protein are highly frequent in tumors and often endow cells with tumorigenic capacities. We sought to examine a possible role for mutant p53 in the cross-talk between cancer cells and their surrounding stroma, which is a crucial factor affecting tumor outcome. Here we present a novel model which enables to individually monitor the response of cancer cells and stromal cells (fibroblasts) to co-culturing. We found that fibroblasts elicit the interferon beta (IFNβ) pathway when in contact with cancer cells, thereby inhibiting their migration. Mutant p53 in the tumor was able to alleviate this response via SOCS1 mediated inhibition of STAT1 phosphorylation. IFNβ on the other hand, reduced mutant p53 RNA levels by restricting its RNA stabilizer, WIG1. These data underscore mutant p53 oncogenic properties in the context of the tumor microenvironment and suggest that mutant p53 positive cancer patients might benefit from IFNβ treatment. As we planned to investigate the effect of mutant p53 we chose to work with lung cancer cells (H1299) which are null for p53 expression and introduce them with two p53 ‘hotsopt’ mutations residing within the DNA binding domain namely R175H and R248Q (H1299175 and H1299248 respectively, Figure 1A and B). The cells were then labeled with a red fluorescent protein (dsRed), while lung CAFs (HK3-T) were labeled with a green fluorescent protein (GFP). The labeled populations were co-cultivated for 24 hours and separated by Fluorescence Associated Cell Sorting (FACS) based on their specific fluorescent marker. RNA was extracted and samples were loaded on chips. Samples were loaded against a common reference sample which contained equal amount of RNA from all samples.
Project description:DAXX and ATRX are tumor suppressor proteins that form a complex with histone H3.3 chaperone and are frequently mutated in cancers with the alternative lengthening of telomeres (ALT), such as pediatric glioblastoma. Rapid loss of function of either DAXX or ATRX are not by themselves sufficient to induce the ALT phenotype. However, cells lacking DAXX or ATRX can be readily selected for ALT-like features. Here, we show that a key feature of ALT selected DAXX and ATRX null glioblastoma cells is the attenuation of p53 function. RNA-seq analysis of DAXX or ATRX null U87 glioblastoma cells with ALT-like features revealed that p53 pathway is among perturbed. ALT-selected DAXX and ATRX-null cells had aberrant response to DNA damaging agent etoposide. Both DAXX and ATRX-null ALT cells showed a loss of p53 binding at a subset of response elements. Complementation of DAXX null cells with wt DAXX rescued p53 binding and transcription, while the tumor associated mutation L130R, that disrupts ATRX binding, was incapable of rescuing p53 chromatin binding. We show that histone H3.3 binding is reduced in DAXX-null cells especially at subtelomeric p53 binding sites and telomere repeats. These findings indicate that DAXX and ATRX function to enable p53 chromatin binding through modulation of histone H3.3 binding, especially at sub-telomeric sites.
Project description:DAXX and ATRX are tumor suppressor proteins that form a complex with histone H3.3 chaperone and are frequently mutated in cancers with the alternative lengthening of telomeres (ALT), such as pediatric glioblastoma. Rapid loss of function of either DAXX or ATRX are not by themselves sufficient to induce the ALT phenotype. However, cells lacking DAXX or ATRX can be readily selected for ALT-like features. Here, we show that a key feature of ALT selected DAXX and ATRX null glioblastoma cells is the attenuation of p53 function. RNA-seq analysis of DAXX or ATRX null U87 glioblastoma cells with ALT-like features revealed that p53 pathway is among perturbed. ALT-selected DAXX and ATRX-null cells had aberrant response to DNA damaging agent etoposide. Both DAXX and ATRX-null ALT cells showed a loss of p53 binding at a subset of response elements. Complementation of DAXX null cells with wt DAXX rescued p53 binding and transcription, while the tumor associated mutation L130R, that disrupts ATRX binding, was incapable of rescuing p53 chromatin binding. We show that histone H3.3 binding is reduced in DAXX-null cells especially at subtelomeric p53 binding sites and telomere repeats. These findings indicate that DAXX and ATRX function to enable p53 chromatin binding through modulation of histone H3.3 binding, especially at sub-telomeric sites.
Project description:DAXX and ATRX are tumor suppressor proteins that form a complex with histone H3.3 chaperone and are frequently mutated in cancers with the alternative lengthening of telomeres (ALT), such as pediatric glioblastoma. Rapid loss of function of either DAXX or ATRX are not by themselves sufficient to induce the ALT phenotype. However, cells lacking DAXX or ATRX can be readily selected for ALT-like features. Here, we show that a key feature of ALT selected DAXX and ATRX null glioblastoma cells is the attenuation of p53 function. RNA-seq analysis of DAXX or ATRX null U87 glioblastoma cells with ALT-like features revealed that p53 pathway is among perturbed. ALT-selected DAXX and ATRX-null cells had aberrant response to DNA damaging agent etoposide. Both DAXX and ATRX-null ALT cells showed a loss of p53 binding at a subset of response elements. Complementation of DAXX null cells with wt DAXX rescued p53 binding and transcription, while the tumor associated mutation L130R, that disrupts ATRX binding, was incapable of rescuing p53 chromatin binding. We show that histone H3.3 binding is reduced in DAXX-null cells especially at subtelomeric p53 binding sites and telomere repeats. These findings indicate that DAXX and ATRX function to enable p53 chromatin binding through modulation of histone H3.3 binding, especially at sub-telomeric sites.
Project description:p53-/- HCT116 cells transduced with the control empty vector or vectors expressing wtp53 or R175H mutp53 were employed for co-IP followed by LC-MS/MS analysis. The potential wtp53 or R175H mutp53-interacting proteins are listed.