Nestin expression in primary and metastatic uveal melanoma - possible biomarker for high-risk uveal melanoma

PurposeNestin, a member of the intermediate filament protein family, has been described as a putative cancer stem cell marker (CSC) in uveal melanoma and poor prognostic factor in a variety of tumours, including cutaneous melanoma. In this study, we examined the expression of nestin in primary (PUM) and metastatic uveal melanoma (MUM) samples, and correlated the findings with histological, clinical and survival data. MethodsNestin expression was assessed by immunohistochemistry in 141 PUM and 26 MUM samples; 11 PUM cases were matched with their corresponding metastases. The percentage of tumour cells expressing nestin was scored by three independent observers. Statistical analysis of all data was performed with SPSS. ResultsNestin expression was identified in both the cytoplasm and membrane of UM cells. Increased expression of nestin in PUM samples was associated with known poor prognostic parameters, including epithelioid cell morphology (p<0.001), closed loops (p=0.001), higher mitotic count (p<0.001), monosomy 3 (p=0.007) and chromosome 8q gain (p<0.001). Primary uveal melanoma (PUM) with nestin expression levels above a cut-off value of 10% [as determined by receiver operating characteristic (ROC) analysis] was associated with a significantly reduced survival time (Log-rank, p=0.002). In MUM, a higher percentage of nestin-positive tumour cells combined with poor prognostic markers in the PUM led to a shorter survival time following the development of metastases. ConclusionIn conclusion, increased nestin expression in PUM is a predictor of a tumour phenotype associated with metastatic progression and reduced survival time at onset of metastasis.