Uveal melanoma is the most common primary malignant intraocular tumor in adults. Metastatic disease of the liver is the leading cause of death in uveal melanoma patients and there is currently no effective treatment. Developing and testing therapies for uveal melanoma has been hampered by the absence of a satisfactory animal model in which uveal melanocytes are transformed in situ and metastasize to the liver. In addition, few murine melanoma cell lines of ocular origin are available for studies aimed at understanding the mechanisms of immune evasion and liver metastasis by uveal melanoma. The objective of this proposal is to develop an SV40 T-antigen (Tag) transgene with elements that allow inducible expression of SV40 Tag by the tyrosinase promoter in the presence of Cre-recombinase. This transgene will permit inducible in situ transformation of pigmented tissues, including melanocytes, in C57BI/6 mice, by targeted drug delivery into the anterior or posterior segments of the eye to induce Cre-recombinase activity. These mice will be used to characterize the immune response to primary and metastatic uveal melanoma by monitoring SV40 Tag- specific immune responses. The immune response to SV40 Tag is well characterized in C57BI/6 mice and tetramers composed of soluble MHC Class I : SV40 Tag peptides are available along with an SV40 Tag specific TCR transgenic strain for studies aimed at determining the fate of CD8+ tumor-specific T cells in primary and metastatic uveal melanoma. In addition, these SV40 Tag transgenic mice will be a source for generating uveal melanoma cell lines. As the tyrosinase promoter is also active in cutaneous melanocytes, this transgenic mouse strain may also serve as a model of cutaneous melanoma which is inducible by drug delivery to the skin. Comparison of uveal and cutaneous melanoma cell lines derived from SV40 Tag transgenic mice may reveal novel molecules that control immune evasion and liver metastasis associated with uveal but not cutaneous melanoma. Understanding the mechanisms of immune evasion by uveal melanomas may lead to therapeutic approaches to promote tumor elimination. Furthermore, manipulation of these immune-suppressive mechanisms may be employed to inhibit T cell responses to prolong graft transplantation in the eye, for example, RPE transplants, or mitigate T cell mediated autoimmune uveitis.
