PD-1 expression on uveal melanoma induces tumor proliferation and predicts poor patient survival

Introduction: Uveal melanoma is one of the most common primary intraocular malignant tumors with poor prognosis and limited treatments. Programmed cell death receptor-1 (PD-1) blockade represents the primary treatment strategy of immune checkpoint inhibition; however, there is a lack of studies on whether PD-1 expression in primary (ocular) uveal melanoma affects tumor progression. Methods: PD-1 expression in 82 cases of primary (ocular) uveal melanoma was detected by immunohistochemistry. The clinical significance of PD-1 expression was evaluated using univariate and multivariate analysis. PD-1 overexpression and knockdown studies were conducted in C918 and Mum-2B cell lines to analyze the effect of PD-1 expression on tumor cell proliferation and intracellular cell signaling transduction. real-time qPCR (RT-qPCR) and western blot analysis were performed to investigate the gene expression level. CCK8 assays were performed to examine the cell proliferation ability. Results: High expression of primary (ocular) intratumor PD-1 was associated with poor patient survival. Moreover, PD-1 expression was correlated with the largest tumor diameter. PD-1 expression and optic nerve invasion were independent prognostic risk factors. PD-1 overexpression in uveal melanoma cell lines promoted tumor cell proliferation, while knockdown of PD-1 inhibited cell proliferation capacity. Conclusion: Our study established the role of PD-1 in the progression of uveal melanoma and provided a new potential treatment selection for uveal melanoma.