GDF11 upregulation independently predicts shorter overall-survival of uveal melanoma

Abstract

Growth differentiation factor 11 (GDF11), is a member of the transforming growth factor-beta (TGF-β) superfamily and bone morphogenetic protein (BMP) subfamily. In this study, we aimed to assess the expression profile of GDF11, its prognostic value in terms of OS, as well as the potential mechanisms leading to its dysregulation in uveal melanoma. A retrospective study was conducted using our primary data and genetic, clinicopathological and overall survival (OS) data from the Cancer Genome Atlas-Uveal Melanoma (TCGA-UVM). Results showed that GDF11 expression was significantly higher in tumor tissues compared with that in adjacent normal tissues. High GDF11 expression was associated with uveal melanoma in advanced stages (IV), epithelioid cell dominant subtype, as well as extrascleral extension. Univariate analysis showed that older age, epithelioid cell dominant, with extrascleral extension and increased GDF11 expression were associated with unfavorable OS. Multivariate analysis confirmed that GDF11 expression was an independent prognostic indicator of unfavorable OS (HR: 1.704, 95%CI: 1.143-2.540, p = 0.009), after adjustment of age, histological subtypes and extrascleral extension. Among the 80 cases of uveal melanoma, only 3 cases had low-level copy gain (+1) and 2 cases had heterozygous loss (-1). No somatic mutations, including SNPs and small INDELs were observed in GDF11 DNA. The methylation of these four CpG sites had weakly (cg22950598 and cg23689080), moderately (cg09890930), or strongly (cg05511733) negative correlation with GDF11 expression. In addition, the patients with high methylation of these four sites had significantly better OS compared to the group with low methylation. Based on these findings, we infer that methylation modulated GDF11 expression might be a valuable prognostic biomarker regarding OS in uveal melanoma.

Fig 1. GDF11 expression in uveal melanoma and adjacent normal tissues.

qPCR analysis of GDF11 expression in 19 cases of uveal melanoma and adjacent normal tissues. 2^-ΔΔCT method was used to assess relative GDF11 expression.

Fig 2. GDF11 expression profile in uveal melanoma.

A-F. Heatmaps (A, C and E) and plot charts (B, D and F) showing the comparison of GDF11 expression in different pathological stages (A-B), between epithelioid cell dominant and spindle cell dominant subtypes (C-D) and between cases with or without extrascleral extension (E-F). G. Comparison of GDF11 expression between deceased and living UVM patients. Original data were obtained from TCGA-UVM.

Fig 3. Kaplan-Meier curves of OS in patients with uveal melanoma.

A. ROC curves and AUC statistics to evaluate the prognostic value of GDF11 expression regarding to death in UVM patients. B. Kaplan-Meier curves of OS in patients with uveal melanoma. Patients were grouped according to median GDF11 expression. Original data were obtained from TCGA-UVM.

Fig 4. Genetic alterations of GDF11 DNA in uveal melanoma.

A. Heatmap showing the correlation between GDF11 expression and its DNA CNAs/somatic mutations. B. Plots chart showing the expression of GDF11 in different CNA groups. Original data were obtained from TCGA-UVM.

Fig 5. Methylation modulated GDF11 expression was a valuable prognostic biomarker in uveal melanoma.

A. Heatmap showing the correlation between GDF11 expression and the methylation status of 15 CpG sites in uveal melanoma. B. Summary of the correlations between GDF11 expression and the methylation status of 15 CpG sites. C. Kaplan-Meier curves of OS in patients with uveal melanoma. Patients were grouped according to median methylation of cg22950598, cg09890930, cg05511733 and cg23689080. Original data was obtained from TCGA-UVM. D. Comparison of the β value of cg05511733 methylation level in 19 primary tumor and adjacent normal tissues.