Doctor of Philosophy (PhD), Ohio University, 2010, Chemistry and Biochemistry (Arts and Sciences)

Melanoma is an aggressive form of skin cancer with high occurrence in the United States. Interferon α2b (IFNα2b/IFNα2) has been used in high doses to treat melanoma. However, problems associated with small therapeutic proteins, such as with interferon treatment, include degradation by serum proteases and rapid kidney clearance because of small molecular size. Pegylation increases the size of the molecule but creates a host of other issues, such as decrease receptor binding, non-specific chemical derivatization, low overall yields and additional purification steps. In this study we used an alternative approach of IFN produced as an arabinogalactan fusion protein in plant cells. These IFN analogues bind to IFN receptors and follow the IFN induced JAK-STAT signaling pathway in melanoma cells. Experiments also demonstrate that these fusion proteins of higher molecular weight cause similar growth inhibition and affect cell cycle distribution. Further, the fusion proteins increased translation of 2'5' OAS1 and PKR, known IFN induced proteins, showing similar downstream signaling as native recombinant IFNα2. The tumor suppressor p53 gets activated in response to DNA damage and has interferon stimulated response elements (ISREs) in its promoter region and hence can be induced by IFN. Additionally, it has a significant role in mediating apoptosis by activating several intracellular pathways as well as up regulating proteins involved in cell cycle arrest. In this study we show that the fusion analogue IFNα2-(SO)20,as well as recombinant IFNα2b, were able to stabilize p53 protein levels and its pro-apoptotic target Bax. Also, there was a decrease in HDM2 levels, the negative regulator of p53. These results suggest that p53 is a downstream signaling target of IFNs and has a possible role in IFN mediated effects in these melanoma cells.

Committee: Susan Evans PhD (Advisor); Xiaozhuo Chen PhD (Committee Member); Marcia Kieliszewski PhD (Committee Member); Glen Jackson PhD (Committee Member) Subjects: Biochemistry