P02 Potential for the loss of endothelial AMBRA1 expression in the tumour microenvironment to identify high-risk patient subsets with nonulcerated AJCC stage I/II melanoma

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Abstract With the recent inclusion of adjuvant therapy for the management of patients with AJCC stage II melanomas there is increased emphasis on the identification of both prognostic and companion biomarkers for early-stage tumours. The expression of AMBRA1 and loricrin (AMBLor) in the epidermis overlying early-stage nonulcerated primary melanomas has recently been identified as a prognostic biomarker able to identify genuinely low-risk tumour subsets. Pilot data also show that loss of AMBLor is associated with loss of AMBRA1 expression in the surrounding tumour endothelium. The aim of the present study was therefore to define the potential of endothelial AMBRA1 expression to identify AJCC stage I/II melanomas at risk of metastasis. Endothelial AMBRA1 expression was determined in a cohort of 48 AJCC stage I/II melanomas previously subjected to automated immunohistochemical analysis for AMBRA1 expression and defined as tumours with loss of AMBLor. Endothelial AMBRA1 expression determined by positive pixel count using Aperio Image-Scope and normalized to vessel area, revealed variable AMBRA1 expression in the intra- and/or peritumoral vessels within 500 µm of the tumour mass. Further analysis revealed a significantly increased proportion of intra-/peritumoral vessels (23.7%) with low AMBRA1 (< 50% of mean total vessel expression) in melanomas that metastasized vs. 12.4% of vessels with low AMBRA1 expression in tumours that remained localized (P = 0.002). Kaplan–Meier analysis additionally demonstrated a significant reduction in 5-year recurrence-free survival (RFS) to 33% for patients with melanomas with > 12% intra-/peritumoral vessels with reduced AMBRA1 expression vs. 76% RFS for patients with < 12% intra-/peritumoral vessels in which AMBRA1 expression was reduced (hazard ratio 5.16, 95% confidence interval 2.05–13; P = 0.003). Collectively, these data suggest that endothelial AMBRA1 expression may serve as a prognostic and companion biomarker to identify and stratify high-risk subsets of patients with early-stage melanoma for adjuvant treatment.

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