Schwann Cell Expression Pattern in Human Melanomas: In Silico and Immunohistochemical Analyses

Considerable interest has recently grown toward the role Schwann cells (SCs) play in controlling the growth of several tumors. TCGA human melanoma database was interrogated focusing on 30 genes preferentially expressed in SCs and not present in melanoma (here referred to as SC-signature). The KM-plotter platform was exploited to address the relation of SC-signature to survival in melanoma patients and in other tumors as specificity controls. In addition, PCA in the GEPIA2 portal was used to address whether the SC-signature discriminates melanomas vs. healthy controls. Finally, the expression of one of the components of the SC-signature (Growth-Associated Protein 43, GAP43) was analyzed by immunohistochemistry. High levels of SC-signature expression were found to correlate inversely with survival in melanoma (423 patients) with strong statistical significance (HR = 2.12, p = 0.000003). A permutation test and validation on an independent melanoma database supported the relevance of these findings. PCA of the SC-signature revealed its capacity to discriminate melanomas from healthy controls. Consistently, immunohistochemical analysis revealed high expression of GAP43 in melanomas compared with control nevi. We have identified a group of 30 genes (SC-signature) whose expression negatively correlates with survival in melanoma patients, representing a promising prognostic biomarker candidate.