XIST unmethylated DNA fragments in male-derived plasma as a tumour marker for testicular cancer.

Testicular germ-cell tumours (TGCTs) are the most common malignant diseases among men aged 20-40 years. We developed a DNA tumour marker for TGCTs based on the unmethylated DNA profile of a neoplasm. The 5' end of the XIST gene is mainly hypomethylated in TGCTs irrespective of XIST expression. Male somatic cells, however, show complete methylation through the CpG sites, including the minimum promoter and XIST-conserved repeats. Identification of a XIST unmethylated fragment in male plasma might be diagnostic for TGCTs.