In vivo application of histone deacetylase inhibitor trichostatin-a impairs murine male meiosis.

In vivo application of histone deacetylase (HDAC) inhibitor trichostatin-A (TSA) in mice results in male infertility. To get more insight into the mechanisms underlying this phenomenon, we performed a genome-wide expression analysis and investigated HDAC activity and degree of histone H3 and H4 acetylation in murine testes after TSA treatment. A significant decrease in HDAC activity and a weak increase in histone acetylation could be demonstrated at 2.5, 5.0, and 7.5 hours after TSA application. Gene expression analysis revealed 507 significantly regulated genes. Transcripts expressed in the somatic cells of the testis (Sertoli, Leydig, peritubular cells, and testis macrophages) or extratubular matrix were regulated as early as 2.5 hours after TSA application, whereas very few meiosis-specific genes were modulated after TSA treatment. In addition, members of the p53-noxa-caspase-3 proapoptotic pathway were regulated early. Applying in-situ hybridization, caspase-3-mRNA was found only in apoptotic spermatocytes, whereas TRP53/p53- and PMAIP1/noxa-mRNA could be demonstrated in spermatogonia and spermatocytes. Our data suggest that TSA impaired male meiosis, possibly through an indirect mechanism implicating somatic cells of the testis.

Genome-wide expression profiling reveals new insights into pathogenesis and progression of testicular germ cell tumors.

Testicular germ cell tumors (GCT) are the most frequent malignancy in young adults and arise from intratubular germ cell neoplasia undetermined (IGCNU, also referred to as carcinoma in situ, CIS). To determine the transcriptional programs involved in the transition from normal germ cells to GCT, and to further elucidate genetic differences between seminomas and non-seminomatous GCT the global expression profile of 12 neoplastic and 3 normal testicular tissues were investigated by whole genome cDNA microarrays. Transcriptional differences between seminomas and embryonal carcinomas were determined and gene signatures characterizing histological subtypes of GCT were identified. The most significant difference between seminomas and embryonal carcinomas was the expression of spermatogenesis-associated genes (PRAME, MAGEA4, SPAG1, HPX) in seminomas and regulatory genes DNMT3B and SOX2 as well as small molecular weight keratins KRT8, KRT18 in embryonal carcinomas. The expression of several selected genes (CK18, MAGE-A4, SOX2, DNMT3B, CD30, KIT) was studied by immunohistochemistry or reverse transcriptase-polymerase chain reaction (RT-PCR) in a large collective of GCT. In summary, our data identified tumor type-specific gene signatures of GCT and provided new insights into genetic pathways driving the transition to seminomas and embryonal carcinomas from their respective precursor lesions.

Gene expression profiling identifies new biological markers of neoplastic germ cells.

BACKGROUND: There is only limited knowledge about gene expression in human testicular germ cell tumors of adolescents and adults (TGCTs), and, in particular in its preinvasive stage intratubular germ cell neoplasia unclassified (IGCNU). MATERIALS AND METHODS: Global gene expression was studied in 10 invasive human testicular germ cell tumors (TGCTs), 7 intratubular germ cell neoplasia unclassified (IGCNU) and 3 normal testes. The pattern of expression of several genes was studied by immunohistochemistry on tissue microarrays containing 126 TGCTs, IGCNU, normal testes and in 5 fetal testes. RESULTS: RAS-related genes (KRAS2, RALA, RAB39B) and various core markers of embryonic stem cells were overexpressed in IGCNU compared to normal testes. CD9, PODXL and centromere-specific histone-H3-like protein CENPA were specifically identified in IGCNU, seminomas, embryonal carcinomas and in fetal gonocytes. Embryonic stem cell regulator SOX2 and downstream targets of the Nodal pathway were up-regulated in embryonal carcinoma only but not in IGCNU/seminoma. Preliminary data revealed that the expression profile of IGCNU is dependent on the histology of the adjacent invasive tumor. CONCLUSION: Our study determined the genes involved in early pathogenetic events of neoplastic germ cell formation, provided new insights into genetic pathways driving the transition of embryonal carcinoma and seminoma from IGCNU and identified new biomarkers of neoplastic germ cells such as CD9, CENPA and PODXL.

DNMT1 and HDAC1 gene expression in impaired spermatogenesis and testicular cancer.

DNA methylation catalyzed by DNA methyltransferases (DNMTs) and histone deacetylation catalyzed by histone deacetylases (HDACs) play an important role for the regulation of gene expression during carcinogenesis and spermatogenesis. We therefore studied the cell-specific expression of DNMT1 and HDAC1 for the first time in human testicular cancer and impaired human spermatogenesis. During normal spermatogenesis, DNMT1 and HDAC1 were colocalized in nuclei of spermatogonia. While HDAC1 was additionally present in nuclei of Sertoli cells, DNMT1 was restricted to germ cells exhibiting a different expression pattern of mRNA (in pachytene spermatocytes and round spermatids) and protein (in round spermatids). Interestingly, in infertile patients revealing round spermatid maturation arrest, round spermatids lack DNMT1 protein, while pachytene spermatocytes became immunopositive for DNMT1. In contrast, no changes in the expression pattern could be observed for HDAC1. This holds true also in testicular tumors, where HDAC1 has been demonstrated in embryonal carcinoma, seminoma and teratoma. Interestingly, DNMT1 was not expressed in seminoma, but upregulated in embryonal carcinoma.

In vivo effects of histone-deacetylase inhibitor trichostatin-A on murine spermatogenesis.

The acetylation state of core histones is controlled by two classes of enzymes, histone acetyl transferases (HATs) and histone deacetylases (HDACs). HDAC inhibitors, such as trichostatin-A (TSA), are able to induce cell cycle arrest by stimulating transcription of genes that negatively regulate cell growth and survival. However, little is known about the effect of HDAC inhibitors on spermatogenesis. TSA treatment of cultured murine germ cells from whole testes resulted in an increase of histone H4 acetylation in round spermatids, suggesting that a hypoacetylated state of these cells is important for their normal differentiation. In the present study, the in vivo effects of TSA on murine spermatogenesis were investigated. Subcutaneously applied TSA resulted in a dose-dependent decrease in relative testis weight due to impaired spermatogenesis. No obvious toxic effects of TSA treatment could be found. A second animal experiment confirmed that male mice receiving TSA under the same conditions as in the first experiment became infertile. This phenomenon was completely reversible. No evidence of histone H4 hyperacetylation in round spermatids could be found; however, the number of spermatids significantly decreased with increasing TSA concentrations. Additionally, a dramatic loss of pachytene-diplotene spermatocytes due to increased apoptosis was observed. This suggests that TSA was mainly effective at the level of meiosis. The other male reproductive organs showed no morphological changes compared to controls, suggesting that TSA action on the testis was not mediated by sex hormones.