Tiffany Johnston

Ms. Tiffany Johnston

orcid

Research Focus & Metrics

Academic Career Length

2Years (2025-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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19 January 2026 in Cancers
Verified
Journal Article
Open access
PDF file
Tiffany JohnstonTiffany Johnston
Tiffany Johnston
JWJack Webb
Jack Webb
MBMatthew Borrelli
Matthew Borrelli
ETEmily Tomas
Emily Tomas
APAine Celestina Pucchio
Aine Celestina Pucchio
TSTrevor G. Shepherd
Trevor G. Shepherd
Background/Objectives: Epithelial ovarian cancer (EOC) is often diagnosed at advanced stages, with metastasis driven by spheroid dissemination within the peritoneal cavity. We previously demonstrated that autophagy supports spheroid cell survival and suggest that it contributes to chemoresistance. Unc-51-like autophagy activating kinase 1 (ULK1), a key regulator of autophagy, has emerged as a promising therapeutic target. Here, we evaluated the effects of ULK1 inhibition via MRT68921, alone and in combination with afatinib—a tyrosine kinase inhibitor (TKI) known to induce pro-survival autophagy—in EOC. Methods: High-grade serous (HGSOC) and ovarian clear cell carcinoma (OCCC) cell lines were cultured under adherent and spheroid conditions. Immunoblotting confirmed on-target effects and modulation of autophagy. Autophagic flux was assessed using mCherry-eGFP-LC3 reporter assays. We assessed 96 dose combinations of MRT68921 and afatinib using drug combination matrices, with synergy evaluated via Synergy Finder. Promising combinations were evaluated across multiple EOC spheroid models and patient ascites-derived organoids. Results: MRT68921 inhibited ULK1 activity and reduced autophagic flux in a context-dependent manner while afatinib alone induced autophagy. Their combination produced synergistic effects at select concentrations, impairing spheroid reattachment and viability. However, MRT68921 alone significantly reduced viability across multiple EOC models, including patient ascites-derived organoids. Conclusions: This study is the first to evaluate the combined effects of MRT68921 and afatinib in epithelial ovarian cancer. Our findings demonstrate that ULK1 inhibition via MRT68921 consistently reduces cell viability across multiple ovarian cancer models, supporting ULK1 as a promising therapeutic target. In contrast, combination with afatinib produced limited and context-dependent effects, indicating that further investigation is needed to identify optimal combination strategies for ULK1-targeted therapies.

17 July 2025 in Scientific Reports
Verified
Journal Article
Open access
MBMatthew J. Borrelli
Matthew J. Borrelli
ABAdrian Buensuceso
Adrian Buensuceso
YVYudith Ramos Valdes
Yudith Ramos Valdes
Tiffany JohnstonTiffany Johnston
Tiffany Johnston
JHJacob Haagsma
Jacob Haagsma
TSTrevor G. Shepherd
Trevor G. Shepherd
Epithelial ovarian cancer (EOC) metastasizes predominantly through multicellular aggregates known as spheroids, which disseminate within the peritoneal cavity and initiate secondary disease upon reattachment at distant sites. EOC spheroids resist detachment-induced cell death by upregulating stress responses including AMP-activated protein kinase (AMPK) signaling and AMPK-dependent macroautophagy (autophagy), highlighting these pathways as potential therapeutic targets. Previously, we used a pharmacological approach to putatively identify Ca2+/calmodulin-dependent protein kinase kinase 2 (CAMKKβ, encoded by CAMKK2) as the primary activator of AMPK in EOC spheroids. Herein we have generated CAMKK2 knockout EOC cell lines via CRISPR-Cas9 genome editing to confirm this function of CAMKKβ and explore the impacts of its loss using in vitro and in vivo models of metastatic EOC. CAMKK2 knockout spheroids exhibited decreased AMPK activation, autophagic flux, cell viability, and metastatic potential relative to parental spheroids, and intraperitoneal xenograft tumours lacking CAMKKβ grew slower than their CAMKKβ-intact counterparts. Effect magnitudes varied between cell line models, suggesting context-dependent roles for CAMKKβ in EOC and rationalizing further studies to characterize the underlying mechanisms. Altogether, our findings highlight CAMKKβ as an important contributor to metabolic reprogramming in EOC spheroids and as a potential therapeutic target in the setting of advanced disease.

1 May 2026 in Journal of Thoracic Disease
Verified
Journal Article
Open access
PDF file
Tiffany JohnstonTiffany Johnston
Tiffany Johnston
DBDaniel Breadner
Daniel Breadner
JRJacques Raphael
Jacques Raphael
Biomarker-driven maintenance therapy in extensive-stage-small cell lung cancer: evaluating the SWOG S1929 clinical trial

26 September 2025 in bioRxiv
Verified
Preprint
Open access
TCTyler T. Cooper
Tyler T. Cooper
LVLorena Veliz
Lorena Veliz
FAFarzaneh Afzali
Farzaneh Afzali
CDCédric Djuomessi
Cédric Djuomessi
OHOwen Francis John Hovey
Owen Francis John Hovey
LPLynne-Marie Postovit
Lynne-Marie Postovit
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 (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.

25 August 2026 in Nanoscale Advances
Verified
Journal Article
Open access
TCTyler T. Cooper
Tyler T. Cooper
LVLorena Veliz
Lorena Veliz
FAFarzaneh Afzali
Farzaneh Afzali
CDCédric Djoumessi
Cédric Djoumessi
OHOwen F. J. Hovey
Owen F. J. Hovey
LPLynne-Marie Postovit
Lynne-Marie Postovit
Strong anion exchange enables low-volume enrichment of extracellular vesicles from human and murine ascites, supporting integrated proteomic and single-EV Raman profiling of ovarian cancer biology.

8 August 2025 in Preprints.org
Verified
Preprint
Open access
PDF file
Tiffany JohnstonTiffany Johnston
Tiffany Johnston
MBMatthew Borrelli
Matthew Borrelli
ETEmily Tomas
Emily Tomas
YVYudith Ramos Valdés
Yudith Ramos Valdés
APAine Celestina Pucchio
Aine Celestina Pucchio
TSTrevor G. Shepherd
Trevor G. Shepherd
Background/Objectives: Epithelial ovarian cancer (EOC) is often diagnosed at advanced stages, with metastasis driven by spheroid dissemination within the peritoneal cavity. We previously demonstrated that autophagy supports spheroid cell survival and suggest that it contributes to chemoresistance. Unc-51-like autophagy activating kinase 1 (ULK1), a key regulator of autophagy, has emerged as a promising therapeutic target. Here, we eval-uated the effects of ULK1 inhibition via MRT68921, alone and in combination with afatinib—a tyrosine kinase inhibitor (TKI) known to induce pro-survival autophagy—in EOC. Methods: High-grade serous (HGSOC) and ovarian clear cell carcinoma (OCCC) cell lines were cultured under ad-herent and spheroid conditions. Immunoblotting confirmed on-target effects and modulation of autophagy. Autophagic flux was assessed using mCherry-eGFP-LC3 reporter assays. We assessed 96 dose combinations of MRT68921 and afatinib using drug combination matrices, with synergy evaluated via Synergy Finder. Promising combinations were evaluated across multiple EOC spheroid models and patient ascites-derived organoids. Results: MRT68921 inhibited ULK1 activity and reduced autophagic flux in a con-text-dependent manner while afatinib alone induced autophagy. Their combination produced synergistic effects at select concentrations, impairing spheroid reattachment and viability. However, MRT68921 alone significantly reduced viability across multiple EOC models, including patient ascites-derived organoids. Conclusions: This study is the first to evaluate the combined effects of MRT68921 and afatinib in EOC. Our findings support ULK1 inhibition as a therapeutic strategy with potential enhanced efficacy when combined with afatinib. These results warrant further preclinical investigation to explore the translational potential of ULK1-targeted therapies alone and in combination with TKIs.