Publications by authors named "Mirjam T Epping"

Unlabelled: Prostate cancer is the most prevalent cancer in males, and treatment options are limited for advanced forms of the disease. Loss of the PTEN and TP53 tumor suppressor genes is commonly observed in prostate cancer, whereas their compound loss is often observed in advanced prostate cancer. Here, we show that PARP inhibition triggers a p53-dependent cellular senescence in a PTEN-deficient setting in the prostate.

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Article Synopsis
  • The study investigates castration resistance in prostate cancer by analyzing data from genetic mouse models and patient clinical data.
  • It finds that removing certain genes (Trp53 or Zbtb7a) along with Pten leads to castration-resistant prostate cancer, while castration normally stops tumor growth.
  • The research highlights specific gene expressions (XAF1, XIAP, SRD5A1) as potential indicators for treatment and suggests a combined therapy targeting these genes to overcome resistance.
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The retinoid X receptor (RXR)-agonist bexarotene and the histone deacetylase inhibitor (HDACI) vorinostat are each established monotherapies for cutaneous T-cell lymphomas (CTCLs). We investigated the combination of HDACI and retinoic acid receptor (RAR)/RXR agonists in vitro and in a phase I, multicenter, open-label, two-part dose-escalation study. The combination of bexarotene with a HDACI in vitro leads to cooperative activation of gene transcription and reduction of cell viability in human tumor cell lines.

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We have previously reported a gene expression signature that is a powerful predictor of poor clinical outcome in breast cancer. Among the seventy genes in this expression profile is a gene of unknown function: TSPYL5 (TSPY-like 5, also known as KIAA1750). TSPYL5 is located within a small region at chromosome 8q22 that is frequently amplified in breast cancer, which suggests that TSPYL5 has a causal role in breast oncogenesis.

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To identify potential biomarkers of therapy response, we have previously done a large-scale gain-of-function genetic screen to identify genes whose expression confers resistance to histone deacetylase inhibitors (HDACI). This genetic screen identified two genes with a role in retinoic acid signaling, suggesting that HDACIs target retinoic acid signaling as part of their anticancer effect. We study here a third gene identified in this genetic screen, UNC45A, and assess its role in retinoic acid signaling and responses to HDACIs using cell-based proliferation and differentiation assays and transcriptional reporter gene assays.

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The preferentially expressed antigen in melanoma (PRAME) is expressed in several hematologic malignancies, but either is not expressed or is expressed at only low levels in normal hematopoietic cells, making it a target for cancer therapy. PRAME is a tumor-associated antigen and has been described as a corepressor of retinoic acid signaling in solid tumor cells, but its function in hematopoietic cells is unknown. PRAME mRNA expression increased with chronic myeloid leukemia (CML) disease progression and its detection in late chronic-phase CML patients before tyrosine kinase inhibitor therapy was associated with poorer therapeutic responses and ABL tyrosine kinase domain point mutations.

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Retinoids play key roles in differentiation, growth arrest, and apoptosis and are increasingly being used in the clinic for the treatment of a variety of cancers, including neuroblastoma. Here, using a large-scale RNA interference-based genetic screen, we identify ZNF423 (also known as Ebfaz, OAZ, or Zfp423) as a component critically required for retinoic acid (RA)-induced differentiation. ZNF423 associates with the RARalpha/RXRalpha nuclear receptor complex and is essential for transactivation in response to retinoids.

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Aberrant acetylation has been strongly linked to tumorigenesis, and the modulation of acetylation through targeting histone deacetylases (HDACs) is gathering increasing pace as a viable therapeutic strategy. A genome-wide loss-of-function screen identified HR23B, which shuttles ubiquitinated cargo proteins to the proteasome, as a sensitivity determinant for HDAC inhibitor-induced apoptosis. HR23B also governs tumor cell sensitivity to drugs that act directly on the proteasome.

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Histone deacetylase inhibitors comprise a variety of natural and synthetic compounds, which have in common that they inhibit enzymes that mediate the removal of acetyl groups from a range of proteins, including nucleosomal histones. Histone deacetylase inhibitors have anti-cancer activities in vitro and in vivo and are used in the clinic for the treatment of advanced cutaneous T cell lymphoma. The molecular pathways targeted by these compounds are discussed with an emphasis on the effects of these compounds on retinoic acid signaling.

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Understanding the pathways that are targeted by cancer drugs is instrumental for their rational use in a clinical setting. Inhibitors of histone deacetylases (HDACI) selectively inhibit proliferation of malignant cells and are used for the treatment of cancer, but their cancer selectivity is understood poorly. We conducted a functional genetic screen to address the mechanism(s) of action of HDACI.

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Tumor antigens are of interest as diagnostic and prognostic markers and potential therapeutic targets. The tumor antigen preferentially expressed antigen of melanoma (PRAME) is frequently overexpressed in a wide variety of cancers and is a prognostic marker for clinical outcome. It has been shown recently that PRAME functions as a repressor of retinoic acid signaling.

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Retinoic acid (RA) induces proliferation arrest, differentiation, and apoptosis, and defects in retinoic acid receptor (RAR) signaling have been implicated in cancer. The human tumor antigen PRAME is overexpressed in a variety of cancers, but its function has remained unclear. We identify here PRAME as a dominant repressor of RAR signaling.

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