Update on testicular germ cell tumors

Effect of rapamycin treatment in human seminoma TCam-2 cells through inhibition of G1-S transition

Mammalian target of rapamycin (mTOR) is an important serine/threonine kinase that plays a critical role in several processes including cell cycle, protein synthesis, and energy metabolism. Due to its multiple roles and general dysregulation in cancer, the mTOR pathway is an important target in cancer therapy. However, studies on mTOR activity in seminoma are limited. Therefore, our aim was to investigate the expression of mTOR signaling pathway proteins in the TCam-2 cell line after rapamycin treatment. TCam-2 cells were treated with different concentrations of rapamycin (control (no rapamycin treatment), 4 nM, 20 nM, 100 nM, 500 nM, and 1000 nM rapamycin) for 48 h and 72 h. mTOR, p-mTOR, P70S6K, p-P70S6K, proliferating cell nuclear antigen (PCNA), and caspase-3 expression levels were analyzed by western blot. Apotosis and cell cycle were analyzed by flow cytometry. After 48 h of rapamycin administration, mTOR activity was significantly decreased at 1000 nM (p < 0.05). In addition, P70S6K acitivity significantly decreased in groups at all rapamycin concentrations (***p < 0.001, ****p < 0.0001). After 72 h of rapamycin administration, mTOR pathway activity were significantly decreased at 100, 500, and 1000 nM rapamycin-treated groups (p < 0.05). Moreover, P70S6K expression decreased in all treatment groups (****p < 0.0001). Caspase-3 expression were similar in all groups. While PCNA expression tended to decrease at 48 h in a dose-dependent manner, this decrease was not significant. We detected decreased PCNA expression at 1000 nM rapamycin at 72 h (p < 0.05). The rate of apoptosis increased especially at 1000 nM rapamycin at 72 h (***p < 0.001). On the other hand, according to the results of the cell cycle experiment, G1 phase arrest was detected at all rapamycin doses at 48 and 72 h (***p < 0.001). Our study indicated that 1000 nM rapamycin may inhibit TCam-2 seminoma cells growth by halting cell proliferation through inhibition of G1-S transition. Therefore, we believe that the findings obtained will contribute to the development of new treatment approaches for seminoma patients in the future and in the process of restoring testicular functions and preserving fertility.

Phytoestrogens regulate the proliferation and expression of stem cell factors in cell lines of malignant testicular germ cell tumors

Phytoestrogens have been shown to exert anti-proliferative effects on different cancer cells. In addition it could be demonstrated that inhibition of proliferation is associated with downregulation of the known stem cell factors NANOG, POU5F1 and SOX2 in tumor cells. We demonstrate the potential of Belamcanda chinensis extract (BCE) and tectorigenin as anticancer drugs in cell lines of malignant testicular germ cell tumor cells (TGCT) by inhibition of proliferation and regulating the expression of stem cell factors. The TGCT cell lines TCam-2 and NTera-2 were treated with BCE or tectorigenin and MTT assay was used to measure the proliferation of tumor cells. In addition, the expression of stem cell factors was analyzed by quantitative PCR and western blot analysis. Furthermore, global expression analysis was performed by microarray technique. BCE and tectorigenin inhibited proliferation and downregulated the stem cell factors NANOG and POU5F1 in TGCT cells. In addition, gene expression profiling revealed induction of genes important for the differentiation and inhibition of oncogenes. Utilizing connectivity map in an attempt to elucidate mechanism underlying BCE treatments we found highly positive association to histone deacetylase inhibitors (HDACi) amongst others. Causing no histone deacetylase inhibition, the effects of BCE on proliferation and stem cell factors may be based on histone-independent mechanisms such as direct hyperacetylation of transcription factors. Based on these findings, phytoestrogens may be useful as new agents in the treatment of TGCT.

Establishment and characterization of a new human extragonadal germ cell line, SEM-1, and its comparison with TCam-2 and JKT-1

OBJECTIVE

To describe the establishment and characterization of a human cell line, SEM-1, from a patient diagnosed with a mediastinal seminoma.

METHODS

A small percentage of germ cell tumors develop as primary lesions in extragonadal sites, and the etiology of these tumors is poorly understood. Currently, only 2 cell lines from seminoma patients have been reported, JKT-1 and TCam-2, both derived from the testis. The cell line was characterized by heterotransplantation in Nude mice, cytogenetic studies, immunohistochemical and flow cytometry staining for germ cell tumor biomarkers, quantitative reverse-transcription polymerase chain reaction for cancer testis antigen expression, and BRAF mutation screening with quantitative polymerase chain reaction.

RESULTS

Characterization studies confirmed the human extragonadal seminoma origin of SEM-1 and demonstrated that it had more features in common with TCam-2 than JKT-1. Specifically, SEM-1 was positive for Sal-like protein 4 (SALL-4), activator protein-2γ (AP-2γ), and cytokeratin CAM5.2, and demonstrated heterogeneous expression of stem cell markers octamer-binding transcription factor 3/4, NANOG, c-KIT, SOX17, and SOX2. Cytogenetic analysis revealed a hypotriploid chromosome number, with multiple copies of 12p, but isochromosome 12p and the BRAF mutation V600E were not identified. The cell lines also did not contain the BRD4/NUT gene rearrangement [t(15,19)] seen in midline carcinomas nor did they contain overexpressed nuclear protein in testis (NUT) genes.

CONCLUSION

SEM-1 is the first cell line derived from an extragonadal germ cell tumor showing intermediate characteristics between seminoma and nonseminoma, and as such, is an important model to study the molecular pathogenesis of this malignancy.

Update on testicular germ cell tumors

PURPOSE OF REVIEW

This overview discusses several important developments in testicular germ cell tumors in the last year.

RECENT FINDINGS

Genomic studies are examining gene expression as possible markers for disease relapse and chemotherapy resistance. Optimal treatment strategies for early-stage nonseminomatous tumors continue to evolve, and advanced disease states continue to be challenging entities in terms of optimizing therapy and outcome. Long-term survivorship issues are also being evaluated in this patient population.

SUMMARY

Significant challenges remain for treatment of certain categories of testicular germ cell tumors. Treatment and surveillance paradigms continue to be defined and refined as research in these areas continues.

Variants in or near KITLG, BAK1, DMRT1, and TERT-CLPTM1L predispose to familial testicular germ cell tumour

BACKGROUND

Familial testicular germ cell tumours (TGCTs) and bilateral TGCTs comprise 1-2% and 5% of all TGCTs, respectively, but their genetic basis remains largely unknown.

AIM

To investigate the contribution of known testicular cancer risk variants in familial and bilateral TGCTs.

METHODS AND RESULTS

The study genotyped 106 single nucleotide polymorphisms (SNPs) in four regions (BAK1, DMRT1, KITLG, TERT-CLPTM1L) previously identified from genome-wide association studies of TGCT, including risk single nucleotide polymorphisms (SNPs) rs210138 (BAK1), rs755383 (DMRT1), rs4635969 (TERT-CLPTM1L) in 97 cases with familial TGCT and 22 affected individuals with sporadic bilateral TGCT as well as 871 controls. Using a generalised estimating equations method that takes into account blood relationships among cases, the associations with familial and bilateral TGCT were analysed. Three previously identified risk SNPs were found to be associated with familial and bilateral TGCT (rs210138: OR 1.80, CI 1.35 to 2.41, p=7.03×10(-5); rs755383: OR 1.67, CI 1.23 to 2.22, p=6.70×10(-4); rs4635969: OR 1.59, CI 1.16 to 2.19, p=4.07×10(-3)). Evidence for a second independent association was found for an SNP in TERT (rs4975605: OR 1.68, CI 1.23 to 2.29, p=1.24×10(-3)). Another association with an SNP was identified in KITLG (rs2046971: OR 2.33, p=1.28×10(-3)); this SNP is in high linkage disequilibrium (LD) with reported risk variant rs995030.

CONCLUSION

This study provides evidence for replication of recent genome-wide association studies results and shows that variants in or near BAK1, DMRT1, TERT-CLPTM1L, and KITLG predispose to familial and bilateral TGCT. These findings imply that familial TGCT and sporadic TGCT share a common genetic basis.