Biology subjects

Shepherd, T. G.

Publications and source records attributed to Shepherd, T. G..

3 recordsLinked to original sources

bioRxiv2025

Isolation of Extracellular Vesicles from Minimal Volume Ascites Fluid Using Strong Anion Exchange Magnetic Beads

Ovarian cancer (OC) remains a leading cause of gynecologic cancer mortality due to late-stage diagnosis and limited early detection strategies. Ascites fluid, a pathological hallmark of OC, is a rich source of tumor-derived extracellular vesicles (EVs) that reflect the tumor microenvironment and hold promise for biomarker discovery. However, isolating EVs from minimal ascites volumes (<100 {micro}L) poses technical challenges using conventional methods like ultracentrifugation or size-exclusion chromatography (SEC). This study explores the application of strong anion exchange (SAX) magnetic beads (Mag-Net) for efficient EV isolation from as little as 2 {micro}L of ascites fluid from both murine models and a human patient with mucinous borderline tumor. We demonstrate that SAX achieves robust EV capture at 10{micro}l of input volume, enabling comprehensive proteomic profiling and single-EV surface-enhanced Raman spectroscopy (SERS) with a >2-fold increase in proteomic depth compared to raw ascites. Notably, this study was able to identify 1000 proteins not previously annotated in Vesiclepedia for OC-derived EVs, alongside distinct SERS signatures, highlighting the potential for multiomic analysis. Comparative analysis with UC revealed enhanced proteomic depth obtained with SAX beads, albeit we also observed differential detection of canonical markers (e.g., CD9, CD81) between input volumes of ascites fluid. These findings establish SAX as a scalable, low-input platform for EV-based biomarker discovery, paving the way for improved early detection and molecular insights into OC progression.

biochemistry↗

bioRxiv2023

Comparative analysis of syngeneic mouse models of high-grade serous ovarian cancer

Ovarian cancers often exhibit high rates of recurrence and poor treatment response. Preclinical models that recapitulate the heterogeneity of human disease are critical to develop new therapeutic approaches. While patient-derived models are a powerful tool for testing various therapeutics, their dependence on immune-compromised mice is severely limiting. Syngeneic mouse models, however, allow for the generation of tumours comprising the full repertoire of non-malignant cell types. Here we have performed a comparative analysis of diverse models of high-grade serous ovarian cancer based on transcriptomic profiling of 22 cell line models, and intrabursal and intraperitoneal tumours from 12 models. Among cell lines, we identify distinct features in signalling activity, such as elevated inflammatory signalling in STOSE and OVE16 models, and MAPK/ERK signalling in ID8 and OVE4 models; metabolic features, such as predicted reduction in glycolysis associated with subsets of engineered ID8 subclones; and relevant functional properties, including differences in EMT activation, PD-L1 and MHC class I expression, and predicted chemosensitivity. Finally, we evaluate variability in properties of the tumour microenvironment among models. We anticipate that this work will serve as a valuable resource, providing new insight to help in the selection of models for specific experimental objectives.

cancer biology↗

bioRxiv2019

Context-dependent activation of SIRT3 is necessary for anchorage-independent survival and metastasis of ovarian cancer cells.

Cells must alter their antioxidant capacity for maximal metastatic potential. However, the antioxidant adaptations required for transcoelomic metastasis, which is the passive dissemination of cancer cells in the peritoneal cavity as seen in ovarian cancer, have largely remained unexplored. Contradicting the need for oxidant scavenging by tumor cells is the observation that expression of the nutrient stress sensor and regulator of mitochondrial antioxidant defenses, SIRT3, is suppressed in many primary tumors. We discovered that this mitochondrial deacetylase is however, upregulated in a context-dependent manner in cancer cells. SIRT3 activity and expression transiently increased following ovarian cancer cell detachment and in tumor cells derived from malignant ascites of high-grade serous adenocarcinoma patients. Mechanistically, SIRT3 prevents mitochondrial superoxide surges in detached cells by regulating the manganese superoxide dismutase SOD2. This mitochondrial stress response is under dual regulation by SIRT3. SIRT3 rapidly increases SOD2 activity as an early adaptation to cellular detachment, which is followed by SIRT3-dependent transcriptional increases in SOD2 during sustained anchorage-independence. In addition, SIRT3 inhibits glycolytic capacity in anchorage-independent cells thereby contributing to metabolic changes in response to detachment. While manipulation of SIRT3 expression has few deleterious effects on cancer cells in attached conditions, SIRT3 up-regulation and SIRT3-mediated oxidant scavenging following matrix detachment are required for anoikis resistance in vitro, and both SIRT3 and SOD2 are necessary for colonization of the peritoneal cavity in vivo. Our results highlight the novel context-specific, pro-metastatic role of SIRT3 in ovarian cancer.

cancer biology↗