Date of Graduation
12-2014
Document Type
Dissertation (PhD)
Program Affiliation
Cancer Biology
Degree Name
Doctor of Philosophy (PhD)
Advisor/Committee Chair
Anil Sood
Committee Member
Eric J Wagner
Committee Member
Gary E Gallick
Committee Member
George A Calin
Committee Member
Menashe Bar-Eli
Abstract
In recent years, there has been a growing recognition of the importance of tumor associated microenvironment in the initiation and progression of tumors. However, a mechanistic understanding of the complicated biological interplay between the stromal framework and malignant regions of the tumor remains incompletely understood. In this study, we address mechanisms by which hypoxia in the tumor microenvironment leads to attenuation of miRNA biogenesis by downregulation of two key enzymes, Drosha and Dicer in cancer cells. Previous data from our laboratory had shown the clinical relevance of downregulated Dicer and Drosha in ovarian and other cancer types, but a clear mechanistic understanding is needed for future clinical intervention strategies to curb deleterious effect of miRNA biogenesis downregulation. Using several in vitro techniques, orthotopic in vivo models and clinical patient samples, we demonstrate novel deregulatory mechanisms involved in Dicer and Drosha downregulation under hypoxia. Data from deep sequencing of normoxia and hypoxia treated cells demonstrate clear effect of this downregulation on miRNA maturation. Collectively, we show substantial functional effects of this downregulation on cancer progression under in vivo conditions by use of siRNAs incorporated in liposomes mediated gene silencing. Our work will provide the missing links for this mechanistic understanding, with a goal of novel interventions to rescue the Dicer and Drosha-miRNA biogenesis pathway. The findings described in this thesis have significant clinical implications with respect to understanding mechanisms of tumor growth and metastasis and the design of new therapeutic approaches in cancers.
Keywords
miRNAs, Ovarian Cancer, Hypoxia