Research Initiatives
Spheroids are entities present in the malignant ascites fluid of ovarian cancer patients with late-stage disease; they afford the cells with increased viability, protection from chemotherapeutic insult, and improved capacity to re-attach and grow as secondary tumours in the peritoneal cavity. We routinely perform experiments in which ovarian cancer cells are cultured in suspension, where cells aggregate to form multicellular clusters called spheroids. The overall focus of our research efforts is to decipher the altered signalling pathways and pathophysiological processes that exist in ovarian cancer spheroids to identify new therapeutic vulnerabilities for metastatic disease and to overcome chemo-resistance.
Stress signaling mediated by LKB1 in ovarian cancer metastasis
Incucyte ZOOM video
​Disrupted OVCAR8 spheroid integrity due to knockout of STK11 encoding LKB1
Ovarian cancer cells induce intracellular stress signalling pathways during spheroid formation that facilitate bioenergetic reprogramming and altered cell adhesion mechanisms. These pathobiological changes may promote malignant cell survival, evasion of chemotherapeutics, and enhanced spheroid reattachment for secondary tumour formation We discovered that Liver kinase B1 (LKB1) is a major factor contributing to this broad stress response in ovarian cancer spheroids. Although a classical tumour suppressor, we have demonstrated that ovarian cancer cells and patient tumour samples retain intact LKB1 expression and activity, which are required for spheroid formation, reattachment, and tumour cell metastatic properties in mouse xenografts. We continue to dissect the molecular and biochemical mechanisms of LKB1 activity in ovarian cancer metastasis, and are now pursuing LKB1 as a therapeutic target through new drug discovery studies in collaboration with the Ontario Institute for Cancer Research and others.
Investigation of ovarian tumour dormancy mechanisms in 3D culture models
Geminin
Evidence for tumour cell dormancy within the EOC spheroid core
Ovarian cancer patients undergo aggressive surgery and combination chemotherapy with the goal to achieve minimal residual disease (MRD) for optimum prognosis. However, it remains quite common that patients relapse within months (platinum-resistant) or a few years (platinum-sensitive), meaning residual tumour cells have the capability to remain dormant and evade chemotherapy, before emerging again with renewed growth and metastatic potential. With over a decade of research, we have defined several signalling pathways and processes that are dysregulated in ovarian cancer spheroids and define a "tumour dormancy" phenotype. These include AKT downregulation, autophagy induction, bioenergetic stress activation, epithelial-to-mesenchymal transition, reciprocal bone morphogenetic protein and transforming growth factor beta signalling, and MYC oncoprotein instability. By interrogating the expression and activity of these different pathways, we are seeking new therapeutic vulnerabilities in spheroids by targeting essential cell survival mechanisms supporting tumour dormancy in models of late-stage ovarian cancer.
ULK1 and autophagy as therapeutic targets in ovarian cancer
mCherry-eGFP-LC3B
ULK1 inhibition blocks autophagy in HeyA8 spheroids
Under starvation-like conditions, eukaryotic cells utilize the evolutionarily-conserved process called autophagy to engulf and degrade organelles and macromolecules for energy production and sustain cell viability. Indeed, ovarian cancer cells within spheroids rapidly induce autophagy through the combined activation of AMPK and downregulation of AKT. A target of these two kinases is ULK1, a crucial autophagy initiator. We have demonstrated that ULK1 is expressed and active within ovarian cancer spheroids and is required for autophagy and cell viability. We have new data that genetic ablation of ULK1 in ovarian cancer cells reduces metastatic potential in mouse xenograft models implicating both autophagy-dependent and -independent mechanisms. Our objective for this project is to identify strategies to block ULK1 and autophagy pharmacologically, and find novel ways to synergize with other anti-cancer therapeutics in the setting of advanced ovarian cancer.