Biology subjects

Tyson, K.

Publications and source records attributed to Tyson, K..

3 recordsLinked to original sources

bioRxiv2025

Assessing PARP trapping dynamics in ovarian cancer using a CRISPR-engineered FRET biosensor

Poly(ADP-ribose) polymerase inhibitors (PARPi) have revolutionised the treatment of ovarian high grade serous carcinoma (HGSC), especially those with defective homologous recombination. However, the emergence of resistance poses a critical challenge, as over 50% of patients relapse within three years. The mechanisms underlying changes in PARP trapping, a central aspect of PARPi efficacy, are not well understood due to limitations in current experimental methodologies. Existing techniques lack resolution and throughput, impeding efforts to study PARP trapping dynamics over time with single-cell resolution. Effective tools to study PARP trapping in live cells are urgently needed to elucidate resistance mechanisms and inform therapeutic strategies. To address this, we used CRISPR-Cas9 gene editing to dual-label endogenous PARP1 with EGFP and mCherryFP in OVCAR4 cells to develop a novel intramolecular FRET-based biosensor that enables real-time, single-cell visualization of PARP trapping dynamics in live cells. High-content fluorescence lifetime imaging microscopy (FLIM) revealed dose dependent PARP trapping upon exposure to PARP inhibitor and distinguished between the trapping efficiencies of four different PARPi (veliparib, olaparib, rucaparib, talazoparib). Moreover, we found reduced PARP trapping in PARPi-resistant models, both in vitro and in vivo, providing critical evidence for altered PARP trapping as a resistance mechanism and illustrating the potential of this FRET biosensor to interrogate resistance mechanisms quantitatively. This PARP trapping biosensor represents a transformative advance, enabling dynamic, high-resolution analysis of mechanisms underlying cancer drug resistance. It provides critical insights into the heterogeneity of PARPi resistance, with implications for developing more effective therapies and improving personalised treatment strategies for ovarian cancer patients. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=58 SRC="FIGDIR/small/642798v1_ufig1.gif" ALT="Figure 1"> View larger version (11K): org.highwire.dtl.DTLVardef@1c5ee67org.highwire.dtl.DTLVardef@1a6d101org.highwire.dtl.DTLVardef@e3a2bborg.highwire.dtl.DTLVardef@d0ba03_HPS_FORMAT_FIGEXP M_FIG C_FIG

cancer biology↗

bioRxiv2024

RAS/PI3K pathway mutations sensitise epithelial ovarian cancer cells to a PARP/NAMPT inhibitor combination

The combination of PARP and NAMPT inhibitors (PARPi/NAMPTi) has been explored for the treatment of TNBC, Ewing Sarcoma and high grade serous carcinoma (HGSC). However, dose limiting toxicity has hampered NAMPTi in clinical trials. To maximise the therapeutic window, we set out to identify predictive genomic biomarkers. Bioinformatic analysis and screening of a panel of epithelial ovarian cancer (EOC) cell lines revealed that cells with RAS/PI3K pathway mutations were sensitive to the NAMPTi FK866. Activity of olaparib and FK866 was associated with a reduction in nicotinamide mononucleotide (NMN) and the PARP substrate nicotinamide adenine dinucleotide (NAD+), with coincident increases in ROS production, DNA damage and apoptosis induction. Caspase 3/7 activity was upregulated to a greater extent in RAS/PI3K mutant cell lines. Finally, the combination significantly reduced omental tumour weight and increased overall survival in mice injected with ID8 Trp53-/-;Pten-/- cells. This study highlights the potential of the PARPi/NAMPTi combination in RAS/PI3K pathway mutant EOC.

cancer biology↗

bioRxiv2023

Heme oxygenase-1 expressing omental macrophages as a therapeutic target in ovarian high grade serous carcinoma

Ovarian high grade serous carcinoma (HGSC) remains a disease of poor prognosis that is unresponsive to current immune checkpoint inhibitors. Although PI3K pathway alterations are common in HGSC, attempts to target this pathway have been unsuccessful. We hypothesised aberrant PI3K pathway activation may alter the HGSC immune microenvironment and present a novel targeting strategy. We used both murine models and HGSC patient samples to study the impact of loss of Pten, a negative regulator of PI3K pathway signalling. We identified populations of resident macrophages specifically in Pten null omental tumours. These macrophages derive from peritoneal fluid macrophages and have a unique gene expression programme, marked by high levels of HMOX1 expression, the gene for the enzyme heme oxygenase-1. Targeting resident peritoneal macrophages prevents appearance of HMOX1hi macrophages and in doing so reduces tumour growth. Furthermore, direct inhibition of HMOX1 extends survival in vivo. HMOX1hi macrophages with corresponding gene expression programmes are also identified in human HGSC tumours and their presence correlates with activated tumoural PI3K pathway/mTOR signalling and poor overall survival in HGSC patients. In contrast, tumours with low number of HMOX1hi macrophages are marked by increased adaptive immune response gene expression. Our data suggest that HMOX1hi macrophages represent a potential therapeutic target and biomarker for poor prognosis HGSC.

cancer biology↗