Background: The event of X chromosome inactivation induced by XIST, which is physiologically observed in females, is retained in testicular germ cell tumors (TGCTs), as a result of a supernumerary X chromosome constitution. X chromosome inactivation also occurs in male germline, specifically during spermatogenesis. We aimed to analyze the promoter methylation status of XIST in a series of TGCT tissues, representative cell lines, and testicular parenchyma. Methods: Two independent cohorts were included, comprising a total of 413 TGCT samples, four (T)GCT cell lines, and 86 testicular parenchyma samples. The relative amount of methylated and demethylated XIST promoter fragments was assessed by quantitative methylation-specific PCR (qMSP) and more sensitive high-resolution melting (HRM) methylation analyses. Results: Seminomas showed a lower amount of methylated XIST fragments as compared to non-seminomas or normal testis (p < 0.0001), allowing for a good discrimination among these groups (area under the curve 0.83 and 0.81, respectively). Seminomas showed a significantly higher content of demethylated XIST as compared to non-seminomas. The percentage of demethylated XIST fragment in cell lines reflected their chromosomal constitution (number of extra X chromosomes). A novel and strong positive correlation between the Johnsen’s score and XIST demethylation was identified (r = 0.75, p < 0.0001). Conclusions: The X chromosome inactivation event and demethylated XIST promoter are promising biomarkers for TGCTs and for assessing spermatogenesis quality.

Additional Metadata
Keywords Methylation, Molecular biomarkers, Spermatogenesis, Testicular germ cell tumors, XIST promoter
Persistent URL dx.doi.org/10.3390/cancers11091385, hdl.handle.net/1765/120323
Journal Cancers
Citation
Lobo, J. (João), Nunes, S.P. (Sandra P.), Gillis, A.J.M. (Ad J. M.), Barros-Silva, D. (Daniela), Miranda-Gonçalves, V. (Vera), van den Berg, A. (Annette), … Looijenga, L.H.J. (2019). XIST-promoter demethylation as tissue biomarker for testicular germ cell tumors and spermatogenesis quality. Cancers, 11(9). doi:10.3390/cancers11091385