UBC Theses and Dissertations
Aurora kinase A, regulated by HMMR and TPX2, controls cell migration and engraftment via centrosome polarization Chu, Tony Lok Heng
BACKGROUND- Cell migration and proliferation are hallmarks of carcinoma cells. These critical processes are often perceived as independent, but the control of microtubule nucleation at centrosomes may interconnect them. HYPOTHESIS- Aurora kinase A (AURKA) – hyaluronan mediated motility receptor (HMMR) – targeting protein for XKlp2 (TPX2), which control microtubule nucleation during mitosis, enable cancer cell engraftment and migration via microtubule organization at polarized centrosomes. METHODS AND RESULTS- We measured the engraftment kinetics of breast cancer cells in immunocompromised or immunocompetent mice and found that enrichment of cells in G1- phase reduced engraftment kinetics. I then used multi-parameter imaging of wound closure assays to track and measure cell cycle progression and the kinetics of cell migration individually and collectively in both mammary epithelial cells or breast carcinoma cells. I also assessed migratory kinetics following the impairment or overexpression of AURKA activity via small molecular inhibition or lentiviral transduction of green fluorescence protein (GFP)-AURKA, respectively. I found that S-phase or G2-phase cells exhibited an elevated velocity and directionality with front-polarized centrosomes and augmented microtubule nucleation capacity. AURKA, regulated by HMMR-TPX2, enabled this directed cell migration, and the silencing of HMMR dampened kinase activity, which associated with impaired nuclear transport of TPX2. Next, I found that AURKA is specifically expressed in leader cells, which polarize centrosomes towards the leading edge, whereas non-leader cells possess random centrosome polarity. Both the inhibition and ectopic expression of AURKA impacted collective migration as well as the emergence of leader cells. Finally, in 3,922 clinically annotated mammary carcinoma tissues, we find AURKA predicts breast cancer-specific survival and relapse-free survival in patients with estrogen receptor (ER)-negative (n= 941), triple negative phenotype (n= 538), or basal-like subtype (n= 293) breast cancers, but not in those patients with ER-positive breast cancer (n= 2,218). CONCLUSION- Epithelial cell migration relies on the organization of the microtubule cytoskeleton through the AURKA-TPX2-HMMR axis. The establishment of front-rear polarity mediated by AURKA activity in leader cells is one dissectible phenotype within a cohesive sheet of migratory cells. Thus, the AURKA molecular axis offers a therapeutic target for ER-negative breast cancer to potentially reduce the migration, colonization and expansion of metastatic cells.
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