Background: The AP-2 transcription factor regulates the expression of multiple genes associated with cell stability and homeostasis. The loss of AP-2 is a crucial event in the development of malignant melanoma. In this study, we seek to assess the prognostic significance of AP-2 in combination with some of its downstream targets, employing the novel AQUA™ (Automated Quantitative Analysis) technology on a large cohort melanoma tissue microarray (TMA). Methods: A tissue microarray including 214 primary melanomas, 293 metastases, 14 local recurrences, 22 nevi, and 15 cell block controls (including melanoma cell lines and normal melanocytes) was used for the analysis. Automated Quantitative Analysis (AQUA) was done to determine exact expression levels of AP-2 within nuclear, non-nuclear (i.e., cytoplasmic) and total melanocytic compartments. Results: As a transcription factor, AP-2 should be active in the nucleus, while cytoplasmic expression should be associated with loss of function. Analysis of total AP-2 expression showed no association with outcome, but the ratio of cytoplasmic to nuclear AP-2 revealed a significant association with metastases (p=0.0041). Furthermore, this AP-2 ratio was significantly associated with survival (p=0.0003 univariate Cox), with high relative levels of AP-2 in the cytoplasm predicting an unfavorable outcome [Relative Risk: 2.79 (95% CI: 1.61-4.85)]. In the primary specimens, the AP-2 ratio was directly correlated with Breslow depth (R=0.335), and associated with microscopic satellitosis (p=0.0373). The ratio also maintained prediction of poor survival in these specimens [RR: 4.33 (95% CI: 1.29-14.54), p=0.017]. Conclusions: Previous studies have demonstrated that the AP-2 transcription factor is involved in the progression of malignant melanoma, with lower expression in highly metastatic cell lines. In this study, we demonstrate that the subcellular localization of AP-2 is the critical factor in survival prediction. Higher expression of this protein in the cytoplasm relative to the nucleus portends a poor prognosis.

[Proc Amer Assoc Cancer Res, Volume 46, 2005]