Knockdown of thrombospondin 2 inhibits metastasis through modulation of PI3K signaling pathway in uveal melanoma cell line M23.

Thrombospondin 2 (THBS2) expression and its prognostic value have been documented in several types of cancer. Nevertheless, the potential role and clinical significance of THBS2 in uveal melanoma (UM) have never been reported. Thus, in our study, we aimed to explore the clinical significance and prognostic impact of THBS2 in UM. Survival and prognosis analyses were implemented using the Kaplan-Meier method and COX's proportional hazards model based on the clinical data retrieved from The Cancer Genome Atlas (TCGA) database. Colony formation, cell proliferation, invasion and migration assays in M23 cell line were performed to evaluate the effects of THBS2 on UM in vitro. To further reveal whether the dysregulated THBS2 expression regulates the UM metastasis, protein biomarkers including serine-threonine kinase (AKT), p-AKT, phosphoinositide 3-kinase (PI3K), p-PI3K, and p70S6K were measured using Western blotting analysis. THBS2 was up-regulated in metastatic UMs. Relationship of THBS2 expression level with the clinicopathological factors demonstrated that the expression level of THBS2 was significantly correlated to histological type, recurrence, and dead. Univariate as well as multivariate COX analyses demonstrated that THBS2 could serve as an independent prognostic factor for overall survival of UM. The knockdown of THBS2 significantly inhibited the proliferation rate of M23 cells, suppressed the colony numbers of M23 cells, lowered the invasive and migratory cell proportion. Importantly, Western blotting results implicated that THBS2 knockdown significantly decreased the expression level of p-AKT, p-PI3K, and p70S6K in M23 cell line. This is the first study to report that THBS2 may play important roles in UM progression and might be a novel prognosis biomarker for UM.