Graduation Year

2017

Document Type

Dissertation

Degree

Ph.D.

Degree Name

Doctor of Philosophy (Ph.D.)

Degree Granting Department

Medical Sciences

Major Professor

Patricia A. Kruk, Ph.D.

Committee Member

Subhra Mohapatra, Ph.D.

Committee Member

Anne Champeaux, M.D.

Committee Member

Marzenna Wiranowska, Ph.D.

Committee Member

Sandy Westerheide, Ph.D.

Keywords

hyaluronic acid, Urinary biomarkers, computational biology, glycosylation-mediated protein secretion, Cellular invasion, immunohistochemistry, ovarian cancer

Abstract

Ovarian cancer (OC) has the highest mortality among gynecological cancers. The high mortality is associated with the lack of an accurate screening tool to detect disease in early stage. As a result the majority of OCs are diagnosed in late stage. Further, the molecular events responsible for malignant transformation in the ovary remain poorly understood. Consequently, delineating key molecular players driving OC could help elucidate potential diagnostic, prognostic and therapeutic targets.

Receptor for hyaluronan-mediated motility (RHAMM) belongs to a group of hyaladherins, which share a common ability to bind to hyaluronan (HA). Intracellularly, RHAMM is involved in microtubule spindle assembly contributing to cell cycle progression. On the cell surface, loosely tethered RHAMM forms a complex with cluster differentiation 44 and HA to activate cell signaling pathways that promote cellular migration, invasion and proliferation. Since RHAMM is overexpressed in a number of cancer types and it is often associated with an aggressive cancer phenotype, I sought to determine if RHAMM similarly contributes to OC.

I found that RHAMM is overexpressed in clinical specimens of OC by immuno-histochemistry and although both primary and metastatic OCs stain equally for RHAMM, RHAMM staining was most intense among clinically aggressive OC histologic subtypes. Further, using an in vitro model system, I was able to show that OC cells express and secrete RHAMM. Abrogation of RHAMM using silencing RNA technology inhibited OC cell migration and invasion suggesting that RHAMM may contribute, at least in part, to the metastatic propensity of OC.

Since RHAMM lacks an export signal peptide sequence and has not been reported to employ alternate mechanisms for extracellular secretion, I utilized computational analyses to predict post-translational glycosylation events as a novel mode for RHAMM secretion. N- glycosylation inhibitors abrogated RHAMM secretion by OC cells in vitro validating my prediction and identify a novel and potentially unconventional mode for RHAMM secretion.

Lastly, since RHAMM is secreted by OC cells, I sought to determine whether RHAMM could be detected in bodily fluids. In a pilot study, I found that urinary levels of RHAMM are elevated in OC patients as measured by enzyme-linked immunosorbant assays. Decreased urinary RHAMM levels noted following cytoreductive surgery support OC as the source of elevated urinary RHAMM levels. Finally, while obesity was associated with high urinary RHAMM levels in OC patients, combined measurements of urinary RHAMM and serum CA125 improved prediction of OC.

Taken together, the studies described herein suggest that RHAMM contributes to OC and that further studies are warranted to further elucidate the clinical role of RHAMM in OC.

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