Hyaluronan (HA), a secreted polymeric glycosaminoglycan component of extracellular matrices, is essential for cell growth and migration during normal development. Elevated production of HA is associated with several pathological states, including cancer. Studies of human prostate tumor biopsies have demonstrated that HA, not present in normal adult prostate, is dramatically overproduced as a function of disease severity in prostate cancer patients. Tumor cell associated HA is observed in the most invasive cancers and correlates to reduced prognosis for the patient. Overproduction and manipulation of cell surface HA polymers is regulated by the action of hyaluronan synthase enzymes (HAS) and hyaluronidases. Degradation of HA by hyaluronidases produces small oligosaccharide fragments, which are active angiogenic stimuli. The long term goals of the laboratory are to understand how HA accumulation occurs, and how HA synthases and hyaluronidases function in concert to facilitate tumor progression in a physiologically relevant model system. The following specific aims are proposed.
Aim 1 : Determine the relative importance of HA biosynthetic enzymes and HA precursors in promoting HA production and tumorigenesis. The overexpression of HA synthases promotes tumor growth and is likely responsible for HA accumulation. It is unclear how elevated HA synthesis occurs, since HA production directly competes with energy metabolism in the tumor cells. An androgen-stimulated gene, UDP-glucose dehydrogenase, provides the limiting precursor for HA synthase. Coexpression of UDP-glucose dehydrogenase and HA synthase synergistically elevates HA synthesis, so we will assess the independent and concerted impact of these enzymes on tumor promotion.
Aim 2 : Investigate how a balance between HA biosynthesis and degradation in prostate tumor cells regulates phenotype. HA synthase is expected to promote maximal tumor growth only in the presence of hyaluronidase. We have stably selected tumor cell lines for differential expression and coexpression of HA synthase and hyaluronidase. We will use these unique tools to correlate the amount and molecular size of HA produced by the cells with their tumorigenic and metastatic potential following direct prostatic injection.
Aim 3 : Use an inducible system to evaluate the role of HA in tumor growth, regression, and apoptosis. Tetracycline inducible constructs will be used to upregulate HA synthesis in non-tumorigenic prostate tumor cells and to inhibit HA synthesis in highly aggressive prostate tumor cells in an experimentally controlled fashion. The chronological importance of HA in tumorigenesis and its mode of action will be evaluated by eliminating HA production in an established orthotopic tumor and determining vascular density and relative percentages of proliferating and apoptotic cells in tumor sections. ? ? ?
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