TPD52, a candidate gene from genomic studies, is overexpressed in testicular germ cell tumours

Several genomic regions are recurrently over- or underrepresented in testicular germ cell tumours (TGCTs), but only a fraction of their genes change their expression accordingly. Two publications to date have studied DNA copy numbers and associated gene expression changes on a genome-wide level to identify key players in TGCT tumorigenesis. Here, we compare lists of significant genes in these studies, and show that 17 genes are common to both. These include concomitant gain and over-expression of JUB, NRXN3, and TPD52, and loss and under-expression of C11orf70 and CADM1, in addition to 12 overexpressed genes located on the chromosome arm 12p. We performed immunohistochemical analysis of TPD52 on a tissue microarray, which showed complete absence of TPD52 protein in normal germ cells and most intratubular germ cell neoplasias. TPD52 was expressed in two-thirds of seminomas and embryonal carcinomas, and at intermediate frequencies in the more differentiated non-seminomas.