Author response: Expression signature based on TP53 target genes doesn't predict response to TP53-MDM2 inhibitor in wild type TP53 tumors

A number of TP53-MDM2 inhibitors are currently under investigation as therapeutic agents in a variety of clinical trials in patients with TP53 wild type tumors. Not all wild type TP53 tumors are sensitive to such inhibitors. In an attempt to improve selection of patients with TP53 wild type tumors, an mRNA expression signature based on 13 TP53 transcriptional target genes was recently developed (Jeay et al. 2015). Careful reanalysis of TP53 status in the study validation data set of cancer cell lines considered to be TP53 wild type detected TP53 inactivating alterations in 23% of cell lines. The subsequent reanalysis of the remaining TP53 wild type cell lines clearly demonstrated that unfortunately the 13-gene signature cannot predict response to TP53-MDM2 inhibitor in TP53 wild type tumors.

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Decision letter: Expression signature based on TP53 target genes doesn't predict response to TP53-MDM2 inhibitor in wild type TP53 tumors

10.7554/elife.10279.009 ◽

2015 ◽

Keyword(s):

Target Genes ◽

Wild Type ◽

Expression Signature ◽

Mdm2 Inhibitor

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Induction Of p53 Transcription and Apoptosis By XPO1 Inhibition In Mantle Cell Lymphoma

Blood ◽

10.1182/blood.v122.21.3825.3825 ◽

2013 ◽

Vol 122 (21) ◽

pp. 3825-3825

Author(s):

Mariko Yoshimura ◽

Jo Ishizawa ◽

Archana Dilip ◽

Sharon Shacham ◽

Michael Kauffman ◽

...

Keyword(s):

Mrna Expression ◽

Target Genes ◽

Cell Lymphoma ◽

Annexin V ◽

Wild Type ◽

Mantle Cell ◽

Wild Type P53 ◽

P53 Target Genes ◽

Mdm2 Inhibitor ◽

Mrna Expression Levels

Abstract We investigated the pathophysiological significance of MDM2 and the nuclear exporter Exportin 1 (XPO1/CRM1) on p53 transcription and their therapeutic targeting in mantle cell lymphoma (MCL). MCL is currently an incurable B-cell non-Hodgkin's lymphoma. Although TP53 mutations occur rarely (i.e., in 15 to 20% of the cases) in MCL, wild-type p53 is frequently inactivated by gene amplification of BMI1, homozygous deletion of CDKN2A (INK4a/ARF, over-expression of regulatory proteins, or gene deletion. For example, tumor cells may sequester p53 in the cytoplasm via the overexpression of proteins like MDM2 and XPO1 thereby abrogating its transcriptional anti-tumor activity. The selective MDM2 inhibitor Nutlin-3a (Vassilev, 2004) has been reported to induce p53-mediated apoptosis in MCL cells, and recently it was shown that the potent, small molecule Selective Inhibitor of Nuclear Export (SINE) induces apoptosis in MCL cells (Zhang, 2013). mRNA expression levels in MCL patient samples were determined using Oncomine (Compendia Bioscience, Ann Arbor, MI). MDM2 mRNA expression levels were not significantly higher in the MCL samples (n = 8) compared to normal B-cells ( n = 5) (P = 0.27). The MDM2 levels were also not associated with overall disease survival (P = 0.12) at 5 years (n = 63). In contrast, gene expression analysis on the same dataset demonstrated increased XPO1 mRNA expression in the MCL cells versus normal B-cells (P< 0.001). Furthermore, this higher XPO1 expression was associated with poorer prognosis in MCL patients (i.e., median overall survival: 3.2 years in low expression XPO1 cases and 1.9 years in high expression CRM1 cases, P = 0.033). mRNA levels of 11 representative p53 target genes were determined in 2 MCL (i.e., Z-138 and JVM-2) cells and were compared to those of four acute leukemia (i.e., OCI-AML3, MOLM-13, REH and NALM-6) cells. Cells from all six cell lines express wild-type p53. The MDM2 inhibitor Nutlin-3a (5 µM) poorly induced p53 target genes in the Z-138 (1.9 ± 0.12-fold) and JVM-2 cells (2.1 ± 0.23-fold) compared to acute leukemia cells (13.9 ± 5.2-fold) (P< 0.001 in both MCL cells), despite their increased p53 protein levels after Nutlin-3a treatment. The data suggest that p53-mediated transcription may be impaired in MCL via a Nutlin-induced increase in cytoplasmic p53 levels. Next, we treated Z-138 with 2 or 4 mM Nutlin-3a or with 80 or 160 nM KPT-185 for 18 hours and determined mRNA changes in p53 targets. KPT-185 induced p53 target genes more potently than Nutlin-3a (i.e., 2- to 4-times). To investigate the significance of p53-mediated apoptosis, Z-138 and JVM-2 were transduced with lentivirus encoding either negative control shRNA (ShC) or p53-specific shRNA (Shp53) and stable shRNA-expressing cells were generated. The p53-specific shRNA reduced p53 basal levels by 80 to 90%, and p53 knockdown cells were ∼80% less sensitive to Nutlin-3a and ∼60% to KPT-185, indicating that MDM2 or XPO1 inhibition rely on p53 pathway to induce apoptosis. Apoptotic induction by Nutlin-3a and KPT-185 in primary MCL cells were determined in 3 samples with wild-type p53. Treatment-specific Annexin V induction percentage in 2.5 µM Nutlin-3a-treated cells was 40.7 ± 8.0%, while it was 64.5 ± 15.0% in 100 nM KPT-185 treated cells. Treatment of 1 µM KPT-185 led to more prominent apoptosis, as evidenced by 81.8 ± 7.7% annexin V staining. Our data suggest that p53 is a component of MDM2 or XPO1 inhibition-induced apoptosis, and p53 transcription is more potently activated by XPO1 inhibition rather than MDM2 inhibition. Based on these data, we propose that active modulation of p53 by SINE XPO1 antagonism and/or MDM2 inhibition transcription would be beneficial in some cancer types to enhance p53-based cancer therapy. Disclosures: Shacham: Karyopharm Therapeutics Inc.: Employment. Kauffman:Karyopharm Therapeutics Inc.: Employment. Andreeff:Karyopharm Therapeutics Inc.: Research Funding.

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An MDM2 inhibitor achieves synergistic cytotoxic effects with adenoviruses lacking E1B55kDa gene on mesothelioma with the wild-type p53 through augmenting NFI expression

Cell Death and Disease ◽

10.1038/s41419-021-03934-y ◽

2021 ◽

Vol 12 (7) ◽

Author(s):

Thao Thi Thanh Nguyen ◽

Masato Shingyoji ◽

Michiko Hanazono ◽

Boya Zhong ◽

Takao Morinaga ◽

...

Keyword(s):

Wild Type ◽

Inhibitory Effects ◽

Cytotoxic Effects ◽

P53 Expression ◽

Nuclear Factor I ◽

Infected Cells ◽

Wild Type P53 ◽

Mdm2 Inhibitor ◽

P16 Expression

AbstractA majority of mesothelioma specimens were defective of p14 and p16 expression due to deletion of the INK4A/ARF region, and the p53 pathway was consequently inactivated by elevated MDM2 functions which facilitated p53 degradaton. We investigated a role of p53 elevation by MDM2 inhibitors, nutlin-3a and RG7112, in cytotoxicity of replication-competent adenoviruses (Ad) lacking the p53-binding E1B55kDa gene (Ad-delE1B). We found that a growth inhibition by p53-activating Ad-delE1B was irrelevant to p53 expression in the infected cells, but combination of Ad-delE1B and the MDM2 inhibitor produced synergistic inhibitory effects on mesothelioma with the wild-type but not mutated p53 genotype. The combination augmented p53 phosphorylation, activated apoptotic but not autophagic pathway, and enhanced DNA damage signals through ATM-Chk2 phosphorylation. The MDM2 inhibitors facilitated production of the Ad progenies through augmented expression of nuclear factor I (NFI), one of the transcriptional factors involved in Ad replications. Knocking down of p53 with siRNA did not increase the progeny production or the NFI expression. We also demonstrated anti-tumor effects by the combination of Ad-delE1B and the MDM2 inhibitors in an orthotopic animal model. These data collectively indicated that upregulation of wild-type p53 expression contributed to cytotoxicity by E1B55kDa-defective replicative Ad through NFI induction and suggested that replication-competent Ad together with augmented p53 levels was a therapeutic strategy for p53 wild-type mesothelioma.

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TMOD-15. EFFICACY OF THE MDM2 INHIBITOR KRT-232 IN GLIOBLASTOMA PATIENT-DERIVED XENOGRAFT MODELS

Neuro-Oncology ◽

10.1093/neuonc/noaa215.966 ◽

2020 ◽

Vol 22 (Supplement_2) ◽

pp. ii231-ii231

Author(s):

Rachael Vaubel ◽

Ann Mladek ◽

Yu Zhao ◽

Shiv K Gupta ◽

Minjee Kim ◽

...

Keyword(s):

Target Genes ◽

Xenograft Model ◽

Culture Conditions ◽

Patient Derived Xenograft ◽

Fold Induction ◽

Extended Survival ◽

Mdm2 Amplification ◽

Mdm2 Inhibitor

Abstract Non-genotoxic reactivation of p53 by MDM2 inhibitors represents a promising therapeutic strategy for tumors with wild-type TP53, particularly tumors harboring MDM2 amplification. MDM2 controls p53 levels by targeting it for degradation, while disruption of the MDM2-p53 interaction causes rapid accumulation of p53 and activation of the p53 pathway. We examined the efficacy of the small molecule MDM2 inhibitor KRT-232, alone and in combination with radiation therapy (RT), in MDM2-amplified and/or p53 wildtype patient-derived xenograft (PDX) models of glioblastoma in vitro and in vivo. In vitro, glioblastoma PDX explant cultures showed sensitivity to KRT-232, both tumors with MDM2 amplification (GBM108 and G148) and non-amplified but TP53-wildtype lines (GBM10, GBM14, and GBM39), with IC50s ranging from 300-800 nM in FBS culture conditions. A TP53 p.F270C mutant PDX (GBM43) was inherently resistant, with IC50 >3000 nM. In the MDM2-amplified GBM108 line, KRT-232 led to a robust (5-6 fold) induction of p53-target genes p21, PUMA, and NOXA, with initiation of both apoptosis and senescence. Expression of p21 and PUMA was greater with KRT-232 in combination with RT (25-35 fold induction), while stable knock-down of p53 in GBM108 led to complete resistance to KRT-232. In contrast, GBM10 showed lower induction of p21 and PUMA (2-3 fold) and was more resistant to KRT-232. In an orthotopic GBM108 xenograft model, treatment with KRT-232 +/- RT for one week extended survival from 22 days (placebo) to 46 days (KRT-232 alone); combination KRT-232 + RT further extended survival (77 days) over RT alone (31 days). KRT-232 is an effective treatment in a subset of glioblastoma pre-clinical models alone and in combination with RT. Further studies are underway to understand the mechanisms conferring innate sensitivity or resistance to KRT-232.

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Glucocorticoid Receptor Phosphorylation Differentially Affects Target Gene Expression

Molecular Endocrinology ◽

10.1210/me.2007-0219 ◽

2008 ◽

Vol 22 (8) ◽

pp. 1754-1766 ◽

Cited By ~ 157

Author(s):

Weiwei Chen ◽

Thoa Dang ◽

Raymond D. Blind ◽

Zhen Wang ◽

Claudio N. Cavasotto ◽

...

Keyword(s):

Glucocorticoid Receptor ◽

Transcriptional Activation ◽

Leucine Zipper ◽

Target Genes ◽

Divalent Cations ◽

Phosphorylation Site ◽

Transcriptional Response ◽

Receptor Occupancy ◽

Wild Type ◽

Interacting Protein

Abstract The glucocorticoid receptor (GR) is phosphorylated at multiple sites within its N terminus (S203, S211, S226), yet the role of phosphorylation in receptor function is not understood. Using a range of agonists and GR phosphorylation site-specific antibodies, we demonstrated that GR transcriptional activation is greatest when the relative phosphorylation of S211 exceeds that of S226. Consistent with this finding, a replacement of S226 with an alanine enhances GR transcriptional response. Using a battery of compounds that perturb different signaling pathways, we found that BAPTA-AM, a chelator of intracellular divalent cations, and curcumin, a natural product with antiinflammatory properties, reduced hormone-dependent phosphorylation at S211. This change in GR phosphorylation was associated with its decreased nuclear retention and transcriptional activation. Molecular modeling suggests that GR S211 phosphorylation promotes a conformational change, which exposes a novel surface potentially facilitating cofactor interaction. Indeed, S211 phosphorylation enhances GR interaction with MED14 (vitamin D receptor interacting protein 150). Interestingly, in U2OS cells expressing a nonphosphorylated GR mutant S211A, the expression of IGF-binding protein 1 and interferon regulatory factor 8, both MED14-dependent GR target genes, was reduced relative to cells expressing wild-type receptor across a broad range of hormone concentrations. In contrast, the induction of glucocorticoid-induced leucine zipper, a MED14-independent GR target, was similar in S211A- and wild-type GR-expressing cells at high hormone levels, but was reduced in S211A cells at low hormone concentrations, suggesting a link between GR phosphorylation, MED14 involvement, and receptor occupancy. Phosphorylation also affected the magnitude of repression by GR in a gene-selective manner. Thus, GR phosphorylation at S211 and S226 determines GR transcriptional response by modifying cofactor interaction. Furthermore, the effect of GR S211 phosphorylation is gene specific and, in some cases, dependent upon the amount of activated receptor.

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A novel PAX5-ELN fusion protein identified in B-cell acute lymphoblastic leukemia acts as a dominant negative on wild-type PAX5

Blood ◽

10.1182/blood-2006-05-025221 ◽

2006 ◽

Vol 109 (8) ◽

pp. 3417-3423 ◽

Cited By ~ 55

Author(s):

Marina Bousquet ◽

Cyril Broccardo ◽

Cathy Quelen ◽

Fabienne Meggetto ◽

Emilienne Kuhlein ◽

...

Keyword(s):

Acute Lymphoblastic Leukemia ◽

B Cell ◽

Target Genes ◽

Lymphoblastic Leukemia ◽

Quantitative Polymerase Chain Reaction ◽

Dominant Negative ◽

Leukemic Cells ◽

Dominant Negative Effect ◽

Wild Type ◽

Cell Acute Lymphoblastic Leukemia

Abstract We report a novel t(7;9)(q11;p13) translocation in 2 patients with B-cell acute lymphoblastic leukemia (B-ALL). By fluorescent in situ hybridization and 3′ rapid amplification of cDNA ends, we showed that the paired box domain of PAX5 was fused with the elastin (ELN) gene. After cloning the full-length cDNA of the chimeric gene, confocal microscopy of transfected NIH3T3 cells and Burkitt lymphoma cells (DG75) demonstrated that PAX5-ELN was localized in the nucleus. Chromatin immunoprecipitation clearly indicated that PAX5-ELN retained the capability to bind CD19 and BLK promoter sequences. To analyze the functions of the chimeric protein, HeLa cells were cotransfected with a luc-CD19 construct, pcDNA3-PAX5, and with increasing amounts of pcDNA3-PAX5-ELN. Thus, in vitro, PAX5-ELN was able to block CD19 transcription. Furthermore, real-time quantitative polymerase chain reaction (RQ-PCR) experiments showed that PAX5-ELN was able to affect the transcription of endogenous PAX5 target genes. Since PAX5 is essential for B-cell differentiation, this translocation may account for the blockage of leukemic cells at the pre–B-cell stage. The mechanism involved in this process appears to be, at least in part, through a dominant-negative effect of PAX5-ELN on the wild-type PAX5 in a setting ofPAX5 haploinsufficiency.

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Evaluating the Influence of a G-Quadruplex Prone Sequence on the Transactivation Potential by Wild-Type and/or Mutant P53 Family Proteins through a Yeast-Based Functional Assay

Genes ◽

10.3390/genes12020277 ◽

2021 ◽

Vol 12 (2) ◽

pp. 277

Author(s):

Paola Monti ◽

Vaclav Brazda ◽

Natália Bohálová ◽

Otília Porubiaková ◽

Paola Menichini ◽

...

Keyword(s):

Dna Sequences ◽

Transcriptional Activation ◽

Target Genes ◽

Relative Activity ◽

Gene Organization ◽

Functional Assay ◽

Wild Type ◽

P53 Family ◽

Transactivation Potential ◽

G Quadruplex

P53, P63, and P73 proteins belong to the P53 family of transcription factors, sharing a common gene organization that, from the P1 and P2 promoters, produces two groups of mRNAs encoding proteins with different N-terminal regions; moreover, alternative splicing events at C-terminus further contribute to the generation of multiple isoforms. P53 family proteins can influence a plethora of cellular pathways mainly through the direct binding to specific DNA sequences known as response elements (REs), and the transactivation of the corresponding target genes. However, the transcriptional activation by P53 family members can be regulated at multiple levels, including the DNA topology at responsive promoters. Here, by using a yeast-based functional assay, we evaluated the influence that a G-quadruplex (G4) prone sequence adjacent to the p53 RE derived from the apoptotic PUMA target gene can exert on the transactivation potential of full-length and N-terminal truncated P53 family α isoforms (wild-type and mutant). Our results show that the presence of a G4 prone sequence upstream or downstream of the P53 RE leads to significant changes in the relative activity of P53 family proteins, emphasizing the potential role of structural DNA features as modifiers of P53 family functions at target promoter sites.

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Crosstalk between p53 and TGF-β Signalling

Journal of Signal Transduction ◽

10.1155/2012/294097 ◽

2012 ◽

Vol 2012 ◽

pp. 1-10 ◽

Cited By ~ 55

Author(s):

Rebecca Elston ◽

Gareth J. Inman

Keyword(s):

Transcriptional Activation ◽

Cancer Biology ◽

Target Genes ◽

Tumour Progression ◽

Signal Transduction Pathway ◽

Mirna Biogenesis ◽

Mutant P53 ◽

Wild Type ◽

P53 Family ◽

Wild Type P53

Wild-type p53 and TGF-β are key tumour suppressors which regulate an array of cellular responses. TGF-β signals in part via the Smad signal transduction pathway. Wild-type p53 and Smads physically interact and coordinately induce transcription of a number of key tumour suppressive genes. Conversely mutant p53 generally subverts tumour suppressive TGF-β responses, diminishing transcriptional activation of key TGF-β target genes. Mutant p53 can also interact with Smads and this enables complex formation with the p53 family member p63 and blocks p63-mediated activation of metastasis suppressing genes to promote tumour progression. p53 and Smad function may also overlap during miRNA biogenesis as they can interact with the same components of the Drosha miRNA processing complex to promote maturation of specific subsets of miRNAs. This paper investigates the crosstalk between p53 and TGF-β signalling and the potential roles this plays in cancer biology.

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In vivo and in vitro oncogenic effects of HIF2A mutations in pheochromocytomas and paragangliomas

Endocrine Related Cancer ◽

10.1530/erc-13-0101 ◽

2013 ◽

Vol 20 (3) ◽

pp. 349-359 ◽

Cited By ~ 76

Author(s):

Rodrigo A Toledo ◽

Yuejuan Qin ◽

Subramanya Srikantan ◽

Nicole Paes Morales ◽

Qun Li ◽

...

Keyword(s):

Somatic Mutations ◽

Target Genes ◽

Germline Mutations ◽

Vascular Tumors ◽

Wild Type ◽

Pheochromocytoma Pc12 ◽

Hereditary Tumors ◽

Tumor Dna

Pheochromocytomas and paragangliomas are highly vascular tumors of the autonomic nervous system. Germline mutations, including those in hypoxia-related genes, occur in one third of the cases, but somatic mutations are infrequent in these tumors. Using exome sequencing of six paired constitutive and tumor DNA from sporadic pheochromocytomas and paragangliomas, we identified a somatic mutation in the HIF2A (EPAS1) gene. Screening of an additional 239 pheochromocytomas/paragangliomas uncovered three other HIF2A variants in sporadic (4/167, 2.3%) but not in hereditary tumors or controls. Three of the mutations involved proline 531, one of the two residues that controls HIF2α stability by hydroxylation. The fourth mutation, on Ser71, was adjacent to the DNA binding domain. No mutations were detected in the homologous regions of the HIF1A gene in 132 tumors. Mutant HIF2A tumors had increased expression of HIF2α target genes, suggesting an activating effect of the mutations. Ectopically expressed HIF2α mutants in HEK293, renal cell carcinoma 786-0, or rat pheochromocytoma PC12 cell lines showed increased stability, resistance to VHL-mediated degradation, target induction, and reduced chromaffin cell differentiation. Furthermore, mice injected with cells expressing mutant HIF2A developed tumors, and those with Pro531Thr and Pro531Ser mutations had shorter latency than tumors from mice with wild-type HIF2A. Our results support a direct oncogenic role for HIF2A in human neoplasia and strengthen the link between hypoxic pathways and pheochromocytomas and paragangliomas.

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