Aims To re-examine and better define the role of Bcl-2, Bcl-XL and Mcl-1 in the progression of melanoma. Materials and Methods Immunohistochemical staining for Bcl-2, Bcl-XL and Mcl-1 were performed on paraffin sections of 100 cases of primary melanomas, metastatic melanomas and benign naevi. The results were correlated with expression of key transcription factors (AP-2, MITF and Stat3) associated with their regulation. Results Bcl-2 was extensively expressed in 100% of benign naevi and melanomas r1.0 mm thick. However, expres- sion was less in melanomas 41.0 mm thick (88%), subcutaneous metastases (62%) and lymph node metas- tases (35%). In contrast, Bcl-XL and Mcl-1 expression increased in metastatic melanoma. Bcl-XL was expressed in 30% of benign naevi, 82% of melanomas r1.0 mm thick, 92% of melanomas 41.0 mm thick, 100% of subcutaneous metastases and 100% of lymph node metastases. Mcl-1 was expressed in 75% of benign naevi, 59% of melanomas r1.0 mm thick, 96% of melanomas 41.0 mm thick, 100% of subcutaneous metastases and 100% of lymph node metastases. Bcl-2 expression was negatively associated with tumour thickness (Po0.05) and the dermal tumour mitotic rate (P ¼ 0.05). However, expression of Bcl-XL and Mcl-1 increased with increasing tumour thickness (Po0.05) and with increased dermal tumour mitotic rate (Po0.05). Univariate analysis revealed that low Bcl-2 expression and high expression of Bcl-XL and Mcl-1 were associated with reduced disease-free survival. Multivariate analysis revealed that these features were dependent on tumour thickness and vascular invasion. Examination of transcription factors revealed a strong correlation between Bcl-2, Bcl-XL, Mcl-1 and nuclear AP-2 expression (Po0.0001), and a weak association with nuclear MITF expression. Bcl-XL but not Mcl-1 expression was corre- lated with the activated form of Stat3. Conclusions The results are the first to show a clear dissociation between changes in Bcl-2 expression (down- regulation) and Bcl-XL, Mcl-1 expression (up-regulation) during progression of melanoma and appear to be associated with changes in transcription factors (AP-2, MITF and Stat3). The findings may have important implications for treatments targeting the anti-apoptotic proteins. BIOLOGY OF EARLY METASTASIS ABS-0017 Loss of maspin expression correlates with increased invasiveness in malignant melanoma A. Denk 1 , M. Bettstetter 1 , P. Wild 1,2 , F. Bataille 1 , W. Dietmaier 1 , A. Bosserhoff 1 1 Institute of Pathology, University of Regensburg, Regensburg, 2 Institute of Pathology, University Medical Center Hamburg, Eppendorf, Germany Purpose of the Study Little is known about expression, regulation and function of serine protease inhibitor (serpin) maspin in malignant melanoma. In this study, we analyzed its role in the progression of malignant melanoma. Description Maspin, first discovered in normal human mammary epithelial cells, can inhibit tumor cell motility and invasion in mammary tumor and prostate carcinoma cell lines. In contrast, overexpression of maspin was found in cancers of pancreas, ovary, lung, thyroid, bladder and colon. However, little is known about the function of maspin in malignant melanoma progression. Therefore, maspin expression was analyzed in malignant melanoma and functional assays for proliferation, migration and invasion in stably maspin-expressing melanoma cell line Mel Im were performed. Additionally, the influence of recombinant maspin was tested in Boyden chamber invasion assay with melanoma cell line Mel Im. Results and Conclusion Loss of maspin expression was investigated in malignant melanoma cell lines compared with normal human melanocytes by quantitative real- time PCR and Western blot analysis and in malignant melanoma in vivo compared with normal skin, analyzed by immunohistochemistry. An analysis of genomic DNA revealed that loss of expression in melanoma cell lines is due to hypermethylation of the maspin promoter. For functional studies, stably maspin-transfected mela- noma cell line Mel Im was tested for changes in cell proliferation, migration and invasion. Although there were no differences in proliferation and migration, a strongly reduced invasive capacity in maspin-expressing cell clones compared with control clones was detected. Furthermore, exogenously added maspin alone was sufficient to reduce invasion in the melanoma cell line Mel Im significantly, indicating that maspin directly inhibits invasion on the cell surface. All these data give new insights into the role of maspin as a tumor suppressor in malignant melanoma. ABS-0018 Knockdown of microphthalmia-associated transcription factor increases melanoma metastatic potential O. Eichhoff 1 , N. Schlegel 1 , C. Fraefel 2 , O. Saydam 2 , R. Dummer 1 , K. Hoek 1 1 University Hospital Zu ¨ rich, 2 Institute of Virology, University of Zu ¨ rich, Zu ¨ rich, Switzerland Abstracts of the Perspectives in Melanoma X and The Third Annual International Melanoma Research Congress, 14–16 September 2006 S11 Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.