Tissue microarray based biomarker study in human cutaneous melanoma

Cancer therapy recently experienced remarkable advances with better understanding of cancer pathogenesis and introduction of new intervention strategies. Biomarkers reflective of the presence of tumor cells, or linked with clinical outcomes, have potential to improve the management of cancers. The purpose of this thesis study is to identify novel biomarkers of human cancers based on tissue microarray (TMA) technology and to determine their value for clinical application in cancer management using melanoma as the model. Melanoma arises from uncontrolled proliferation of melanocytes. Although melanoma accounts for only 4% of all skin cancer, it is responsible for 80% of deaths related to skin malignancies. To discover novel biomarkers of melanoma, we constructed a TMA using biopsies from 707 patients with various stages of melanocytic lesions. Using immunohistochemistry and TMA, multiple biomarker candidates were evaluated, and many were found to have significant prognostic value, including expression loss of Fbw7. To further improve the clinical value of these markers, various combinations of individual markers were evaluated, leading to the identification of KAI1 and p27 that together showed much stronger prognostic value than when used as individual markers. Moreover, since there has been a dearth of reliable prognostic markers to offer prognostic information on specific melanoma stages, we identified the AJCC-stage specific prognostic markers, including BRAF protein expression as a prognostic marker for thin melanomas. In that significant prognostic value was found for Fbw7 protein in melanoma, we performed in vitro experiments on this protein in detail. Our data showed that the alpha isoform of Fbw7, located in the cell nucleus, was the dominant form expressed in melanoma. Knock-down of Fbw7α promoted melanoma cell migration, and the MAPK signaling pathway was required for Fbw7 function in melanoma. These findings indicate loss of Fbw7 to be an independent melanoma prognostic marker, and important for the development of malignant behaviors of melanoma cells. This study has demonstrated that the combination of TMAs of cancers with the corresponding clinical database represents a powerful technological platform for biomarker discovery. TMA/clinical database combination-based investigations should be applicable for the investigation of other types of human cancers as well.Medicine, Faculty ofMedicine, Department ofExperimental Medicine, Division ofGraduat