Biology subjects

Papachristou, E. K.

Publications and source records attributed to Papachristou, E. K..

6 recordsLinked to original sources

bioRxiv2026

IL-1-activated cancer-associated fibroblasts promote STAT1-driven transcriptional reprogramming of pancreatic tumour cells

Pancreatic ductal adenocarcinoma (PDAC) remains one of the deadliest cancers, with limited treatment options and poor survival rates. It is characterised by strong driver mutations, epigenetic reprogramming, and a dense tumour microenvironment (TME). A defining feature of the PDAC TME is its fibrotic stroma, which is largely composed of cancer-associated fibroblasts (CAFs). Distinct CAF populations have been implicated in PDAC progression, but the mechanisms that govern their crosstalk with the cancer cells are poorly understood. We generated genetically engineered pancreatic stellate cells (PSCs) modelling interleukin-1 (IL-1)-dependent inflammatory CAFs (iCAFs) and transforming growth factor-{beta} (TGF-{beta})-dependent myofibroblastic CAFs (myCAFs) to investigate how distinct stromal populations shape the epigenetic landscape of pancreatic ductal adenocarcinoma (PDAC). We found that iCAFs, but not myCAFs, promoted gemcitabine resistance in epithelial tumour cells and identified STAT1 as a critical mediator of iCAF-tumour cell crosstalk. Mechanistically, STAT1 drove the induction of interferon (IFN)-responsive genes, while blockade of IFN-{beta} attenuated iCAF-mediated transcriptional reprogramming. Genetic ablation of STAT1 in tumour cells abolished iCAF-induced chemoresistance and associated transcriptional changes. In an orthotopic in vivo model, STAT1 knockout significantly prolonged survival following gemcitabine treatment, supporting a central role for STAT1 signalling in stromal-driven therapy resistance. We provide a comprehensive analysis on how IL-1-dependent iCAFs contribute to epigenetic reprogramming in PDAC and uncover a previously undescribed role for STAT1 in stromal-epithelial interactions. These findings reveal distinct, non-overlapping mechanisms by which CAF subtypes modulate tumour behaviour and identify STAT1 as a therapeutic vulnerability that can be exploited to sensitise PDAC to standard chemotherapy. Significance statementThis study establishes that the epigenetic landscape of PDAC is differentially shaped by iCAF- and myCAF-like PSCs and defines STAT1 as a mediator of iCAF-induced chemoresistance and transcriptional reprogramming. We demonstrate that genetic ablation of STAT1 sensitises tumours to gemcitabine in vivo, extending survival and positioning STAT1 as an actionable target to overcome stromal-mediated therapy resistance in PDAC.

cancer biology↗

bioRxiv2025

Comparative ASCL1 interactome analysis reveals CDK2-Cyclin A2 as suppressors of differentiation in MYCN-amplified neuroblastoma

Neuroblastoma is a heterogeneous paediatric cancer arising from developmentally arrested neuronal precursors, where restoring differentiation offers therapeutic promise. ASCL1, a pro-neural transcription factor, is widely expressed in neuroblastoma and can drive either proliferation or differentiation depending on the cellular context. Here, we show that distinct MYCN-amplified neuroblastoma cell lines exhibit differing cell cycle and differentiation responses to ASCL1 overexpression. By comparing genome-wide ASCL1 chromatin binding, transcriptional changes, and protein-protein interactions, we found that ASCL1 binds more extensively to neuronal proteins in a cell line that is more susceptible to ASCL1-driven differentiation, but associates with cell cycle regulators in less responsive cells. We show that CDK2-Cyclin A2 bind ASCL1 in less responsive cells, with CDK-mediated phosphorylation of ASCL1 limiting the ability of ASCL1 to drive differentiation. Our study reveals that context-dependent interactions of ASCL1 with protein partners on the chromatin control its ability to re-engage a differentiation program in neuroblastoma.

cancer biology↗

bioRxiv2024

MOZ and HBO1 Histone Acetyltransferase Complexes Are Molecular Dependencies and Therapeutic Targets in NUP98-Rearranged Acute Myeloid Leukemia

NUP98 fusion oncoproteins (FOs) are a hallmark of childhood acute myeloid leukemia (AML) and drive leukemogenesis through liquid-liquid phase separation-mediated nuclear condensate formation. However, the composition and consequences of NUP98 FO-associated condensates are incompletely understood. Here we show that MYST family histone acetyltransferase (HAT) complex proteins including MOZ/KAT6A, HBO1/KAT7, and the common MOZ/HBO1 complex subunit BRPF1 associate with NUP98 FOs on chromatin and within condensates. MYST HATs are molecular dependencies in NUP98-rearranged (NUP98-r) leukemia, and genetic inactivation or pharmacologic inhibition of Moz and Hbo1 impairs NUP98-r cell fitness. MOZ/HBO1 inhibition decreased global H3K23ac levels, displaced NUP98::HOXA9 from chromatin at the Meis1 locus, and led to myeloid cell differentiation. Additionally, MOZ/HBO1 inhibition decreased leukemic burden in multiple NUP98-r leukemia xenograft mouse models, synergized with Menin inhibitor treatment, and was efficacious in Menin inhibitor-resistant cells. In summary, we show that MYST family HATs are therapeutically actionable dependencies in NUP98-r AML. SIGNIFICANCE STATEMENTMOZ and HBO1 associate with NUP98 fusion oncoprotein condensates to drive leukemogenesis. Inhibition of their histone acetyltransferase activity is an effective therapeutic strategy in NUP98-rearranged leukemias, including those resistant to Menin inhibition. Moreover, combined MOZ/HBO1 and Menin inhibition is synergistic, supporting clinical translation to improve outcomes of NUP98 FO-driven leukemias.

cancer biology↗

bioRxiv2023

TRIB1 modulates transcriptional programming in breast cancer cells to regulate cell proliferation

The pseudokinase Tribbles Homolog 1 (TRIB1) is a known driver of tumorigenesis in acute myeloid leukemia and is encoded upstream of the oncogene MYC at the 8q24 locus. We observed that TRIB1/MYC co-amplification is associated with decreased relapse-free and overall survival in breast cancer patients, but the role of TRIB1 in this disease has not been well characterized. TRIB1 knockdown in multiple breast cancer cell lines inhibited cell proliferation and suppressed MYC expression, implicating TRIB1 in breast cancer cell proliferation. Transcriptomic and cell cycle analysis revealed cell cycle regulation as the likely mechanism through which TRIB1 influences breast cancer cell proliferation. TRIB1 knockdown also resulted in significant changes in both estrogen receptor (ER) and {beta}-catenin associated transcription. Interrogating the TRIB1 interactome in breast cancer cells by qPLEX-RIME reinforced the known association between TRIB1 and ubiquitination, while revealing a range of previously undescribed TRIB1 associated factors. Further analysis of the association between TRIB1, {beta}-catenin and FERMT2 suggests TRIB1 may regulate {beta}-catenin activity by controlling the levels of both {beta}-catenin, and its co-factor FERMT2. Together, these results suggest that coregulation of {beta}-catenin and ER-driven transcription by TRIB1, facilitates regulation of MYC expression and breast cancer cell proliferation. SignificanceThe pseudokinase TRIB1 is frequently co-amplified in breast cancers with the potent oncogene MYC, although the functional consequences of this event are not well understood. This study demonstrates TRIB1 is a regulator of cell cycle progression and MYC expression in breast cancer cells. It also profiles TRIB1-associated proteins in breast cancer cells, demonstrating conservation of TRIB1s canonical interaction with COP1 and reveals associations with members of the wider ubiquitination machinery, a range of transcriptional regulators and chromatin remodelers. The data presented provide insight into the function of TRIB1 in breast cancer and the role of TRIB1 in transcriptional regulation.

cancer biology↗

bioRxiv2021

GLP is critical for oogenesis exhibiting a G9A-independent role in transcriptional repression

GLP (EHMT1) is a multifunctional protein, best known for its role as an H3K9me1 and H3K9me2 methyltransferase through its reportedly obligatory dimerization with G9A (EHMT2). Here, we investigate the role of GLP in the oocyte in comparison to G9A using oocyte-specific conditional knockout mouse models (G9a cKO, Glp cKO, G9a-Glp cDKO). Loss of GLP in Glp cKO and G9a-Glp cDKO oocytes re-capitulated meiotic defects observed in the G9a cKO; however, there was a significant impairment in oocyte maturation and developmental competence in Glp cKO and G9a-Glp cDKO oocytes beyond that observed in the G9a cKO. Consequently, loss of GLP in oogenesis results upon fertilisation in mid-gestation embryonic lethality. To assess the molecular functions of GLP and G9A, we applied a multi-omics approach, supported by immunofluorescence, to identify changes in epigenomic, transcriptomic and proteomic signatures in cKO oocytes. H3K9me2 was equally depleted in all cKO oocytes, whereas H3K9me1 was decreased only upon loss of GLP. The transcriptome, DNA methylome and proteome were markedly more affected in G9a-Glp cDKO than G9a cKO oocytes, with transcriptional de-repression associated with increased protein abundance and gains in genic DNA methylation in G9a-Glp cDKO oocytes. Together, our findings suggest that GLP contributes to transcriptional repression in the oocyte, independent of G9A, and is critical for oogenesis and oocyte developmental competence.

developmental biology↗

bioRxiv2021

The distinct effects of MEK and GSK3 inhibition upon the methylome and transcriptome of mouse embryonic stem cells

Mouse embryonic stem cells (mESCs) were first cultured in vitro in serum-containing medium with leukaemia inhibitory factor, in which they exhibit heterogeneous expression of both pluripotency and some early differentiation markers. Over the last decade, however, it has become commonplace to grow mESCs with inhibitors of MEK and GSK3 signalling, which together elicit a more homogeneously naive state of pluripotency. Whilst 2i/L-cultured mESCs have been shown to be globally hypomethylated, a comprehensive understanding of the distinct effects of these signalling inhibitors upon the DNA methylome is still lacking. Here we carried out whole genome bisulphite and RNA sequencing of mESCs grown with MEK or GSK3 inhibition alone, including different time points and concentrations of MEK inhibitor treatment. This demonstrated that MEK inhibition causes a dose-dependent impairment of maintenance methylation via loss of UHRF1 protein, as well as rapid impairment of de novo methylation. In contrast, GSK3 inhibition triggers impairment of de novo methylation alone, and consequent hypomethylation is enriched at enhancers with a 2i/L-specific chromatin signature and coincides with upregulation of nearby genes. Our study provides detailed insights into the epigenetic and transcriptional impacts of inhibiting MEK or GSK3 signalling in mouse pluripotent cells. HighlightsO_LIMEK inhibition causes dose-dependent impairment of maintenance methylation via loss of UHRF1 protein, as well as impairment of de novo methylation. C_LIO_LIGSK3 inhibition triggers impairment of de novo methylation alone, which results in hypomethylation of enhancers and non-CGI promoters. C_LIO_LIEnhancers that are hypomethylated following GSK3 inhibition are enriched for 2i/L-specific pluripotency factor binding, TET2 and H3K4me1. C_LIO_LIEnhancer hypomethylation coincides with increased expression of nearby and Capture Hi-C linked genes. C_LI

developmental biology↗