Disparate Roles of Cell-Cell Contact and Cytokine Secretion in an In Vitro Model of the Seminoma Microenvironment.

Type II testicular germ cell tumors (TGCTs) are the most common solid malignancies in young men and are classified into seminomas and non-seminomatous subtypes. Seminomas are known for their highly pro-inflammatory tumor microenvironment (TME) with abundant immune cell infiltration. While previous work has demonstrated that the seminoma-derived cell line TCam-2 induces immune cell activation in co-culture and undergoes phenotypic changes itself, the underlying mechanisms remained unclear. To explore the role of direct cell-cell interaction and the effects mediated by soluble mediators such as cytokines, we conducted co-culture experiments of TCam-2 cells with purified human T cells or monocytes, including Transwell assays and treatments with IL-6, TNFα, or their respective blocking antibodies Tocilizumab and Adalimumab. In this way, we found that immune cell activation, indicated by enhanced secretion of pro-inflammatory cytokines and an upregulation of activation markers, strongly depended on direct physical contact between both cell types. Nonetheless, we also unveiled the role of soluble mediators in both immune cell activation and promoting a shift in TCam-2 cells from a seminoma-like phenotype to a more dedifferentiated phenotype, suggesting that cytokines critically shape the TME. These observations highlight the complexity of tumor-immune interactions in the seminoma microenvironment, offering new insight into immune-driven dynamics in TGCTs.