The potential effects of poly- and perfluoroalkyl substances (PFAS) are a recently emergent human and environmental health concern. There is a consistent link between PFAS exposure and cancer, but the mechanisms are poorly understood. Although epidemiological evidence supporting PFAS exposure and cancer in general is conflicting, there is relatively strong evidence linking PFAS and testicular germ cell tumors (TGCTs). However, no mechanistic studies have been performed to date concerning PFAS and TGCTs. In this report, the effects of the legacy PFAS perfluorooctanesulfonic acid (PFOS) and the newer “clean energy” PFAS lithium bis(trifluoromethylsulfonyl)imide (LiTFSi, called HQ-115), on the tumorigenicity of TGCTs in mice, TGCT cell survival, and metabolite production, as well as gene regulation were investigated. In vitro, the proliferation and survival of both chemo-sensitive and -resistant TGCT cells were minimally affected by a wide range of PFOS and HQ-115 concentrations. However, both chemicals promoted the growth of TGCT cells in mouse xenografts at doses consistent with human exposure but induced minimal acute toxicity, as assessed by total body, kidney, and testis weight. PFOS, but not HQ-115, increased liver weight. Transcriptomic alterations of PFOS-exposed normal mouse testes were dominated by cancer-related pathways and gene expression alterations associated with the H3K27me3 polycomb pathway and DNA methylation, epigenetic pathways that were previously showed to be critical for the survival of TGCT cells after cisplatin-based chemotherapy. Similar patterns of PFOS-mediated gene expression occurred in PFOS-exposed cells in vitro. Metabolomic studies revealed that PFOS also altered metabolites associated with steroid biosynthesis and fatty acid metabolism in TGCT cells, consistent with the proposed ability of PFAS to mimic fatty acid-based ligands controlling lipid metabolism and the proposed role of PFAS as endocrine disrupters. Our data, is the first cell and animal based study on PFAS in TGCTs, support a pro-tumorigenic effect of PFAS on TGCT biology and suggests epigenetic, metabolic, and endocrine disruption as potential mechanisms of action that are consistent with the non-mutagenic nature of the PFAS class.

Background/Objectives: Testicular germ cell tumors (TGCTs) are uniquely curable with cisplatin-based therapies even when widely metastatic; however, cisplatin resistance does occur, resulting in very poor prognosis. The mechanisms to explain TGCT hypersensitivity to cisplatin and mechanisms of resistance are not well-understood. Methods: The global transcriptional response to acute cisplatin treatment (24 h after a 6 h pulse of cisplatin) was assessed in three parental embryonal carcinoma TGCT cells lines compared to multiple isogenic, stable, cisplatin-resistant clonal lines from these parental cells. Results: Cisplatin treatment of parental cells consistently showed a more robust overall transcriptional response to cisplatin compared to their cisplatin-resistant cellular counterparts for a common set of genes and pathways including the upregulation of genes associated with histone modifications and p53, EMT, and KRAS signaling and the downregulation of genes normally upregulated by MYC. Focusing on genes exclusively altered in parental cells revealed upregulated genes known to be induced by p53 and downregulated by MYC and the transferrin receptor, TFRC1. Several of these p53/MYC/TFRC1 targets were associated with a higher instance of disease-free survival in a cohort of TGCT patients. Conclusions: Cisplatin resistance in TGCT cells is associated with a diminished alteration in cisplatin-responsive genes, especially genes known to be regulated by p53, MYC and TFRC1, that may be linked to cisplatin hypersensitivity and survival in TGCTs.