Comprehensive analysis of metastatic seminoma germ cell tumors shows divergent expression of immune-related pathways.

506 Background: Not much is known about the molecular mechanisms resulting in tumor progression and finally leading to metastasis in testicular germ cell tumor (TGCT). Only a few studies in some other tumor types have identified a limited set of genes, related to invasion, progression or metastases to be distinctly upregulated at the invasive tumor front in metastasized patients. However, systematic investigations are missing. Therefore, regional differences in the TGCT subtype seminomas were investigated to achieve a better understanding of the mechanisms involved in the metastatic process. Methods: Formalin-fixed paraffin embedded (FFPE) tissue samples of patients with clinical stage I disease, no adjuvant therapy and a relapse-free survival of at 2 years (n = 21), and patients showing metastasis (n = 14) were selected for the study. The tumor front (TF) and tumor center (TC) regions of each patient were determined and separately collected using laser capture microdissection. RNA was extracted and a multiplex gene expression analysis was performed on all TF and TC samples using nCounter technology of Nanostring. A panel of 770 transcripts was analyzed using the PanCancer Progression panel. Different bioinformatics tools were employed for analyzing the expression data. Results: Differential gene expression patterns were observed in the metastatic and non-metastatic patients, with respect to both the tumor front and tumor center regions. Ingenuity pathway analysis on the differentially expressed genes showed enrichment of tumor functions like migration, invasion, and angiogenesis at the TF as compared to the TC. Remarkably, prominent inflammatory and cancer related pathways such as IL-6 signaling, acute phase response signaling, NF-κB signaling and, dendritic cell maturation were significantly upregulated in the metastatic versus non-metastatic tumors (z-score > ± 2 and p-value < 0.05). Conclusions: This is the first study showing tumor heterogeneity in TGCTs. Evidently, IL-6 signalling was the most significantly upregulated pathway in the metastatic versus the non-metastatic patients, that could serve as a therapeutic target for personalized therapy.