Oncogenes in human testicular cancer: DNA and RNA studies

Current Insights into Interethnic Variability in Testicular Cancers: Population Pharmacogenetics, Clinical Trials, Genetic Basis of Chemotherapy- Induced Toxicities and Molecular Signal Transduction

Testicular cancer is an aggressive malignancy with a rising incidence rate across the globe. Testicular germ cell tumors are the most commonly diagnosed cancers, and surgical removal of the testes is often a radical necessity along with chemotherapy and radiotherapy. While seminomas are receptive to radiotherapy as well as chemotherapy, non-seminomatous germ cell tumors respond to chemotherapy only. Due to the singular nature of testicular cancers with associated orchiectomy and mortality, it is important to study the molecular basis and genetic underpinnings of this group of cancers across male populations globally. In this review, we shed light on the population pharmacogenetics of testicular cancer, pediatric and adult tumors, current clinical trials, genetic determinants of chemotherapy-induced toxicity in testicular cancer, as well as the molecular signal transduction pathways operating in this malignancy. Taken together, our discussions will help in enhancing our understanding of genetic factors in testicular carcinogenesis and chemotherapy-induced toxicity, augment our knowledge of this aggressive cancer at the cellular and molecular level, as well as improve precision medicine approaches to combat this disease.

A long-term survivor of metastatic neuroendocrine prostate cancer treated with multimodal therapy: genetic consideration from next-generation sequencing

It is still unclear whether cell-free DNA (cfDNA) can replace solid-tissue biopsy. A 59-year-old man developed castration-resistant prostate cancer with a liver metastasis. We performed a liver biopsy and collected a cfDNA sample. Although he underwent radiofrequency ablation, tumors recurred and he was transferred to another hospital. We performed next-generation sequencing using DNA from the biopsy tissue and cfDNA. BRCA2 p.T3033fs and AURKA F31I were detected in both the biopsy tissue and the cfDNA. cfDNA may be useful as a liquid biopsy for monitoring the gene profile of aggressive prostate cancer.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13691-021-00482-2.

C-Myc Deregulation is Involved in Melphalan Resistance of Multiple Myeloma: Role of PDGF-BB

Oncogenes are important regulators of cancer growth and progression and their action may be modulated by proteins of the growth factor family, such as angiogenic cytokines, known to be strongly involved in neoplastic evolution. Reciprocal interactions between oncogenes and angiogenic modulators may represent, in haematological neoplasms, including multiple myeloma (MM), a possible mechanism of drug resistance. The aim of this work is to investigate in vitro and in vivo whether or not c-myc deregulation is involved in the melphalan resistance elicited by myeloma patients and consequently to clarify the role of the angiogenic factor PDGF-BB in modulating c-myc protein expression. Fifty-one MM patients on chemotherapy with melphalan were analyzed for structural alterations of the c-myc gene, c-Myc protein expression, as well as for serum PDGF-BB release. For the in vitro study, two M14-derived established cell clones, differing for the c-Myc protein expression (c-Myc low -expressing or constitutively expressing clones) were used. Our results show that PDGF-BB is able to up-regulate Myc expression and reduce melphalan sensitivity of tumor cell clones, constitutively expressing c-myc gene product. In addition, down-regulation of c-Myc protein induces the expression of PDGF-β receptor molecules and reduces PDGF-BB release. In agreement with these results, in vivo data show that melphalan-resistant MM patients present overexpressed c-Myc protein and higher serum PDGF-β receptor levels compared to minor responding patients.

Role of platelet-derived growth factors in the testis

Normal development and function of the testis are controlled by endocrine and paracrine signaling pathways. Platelet-derived growth factors (PDGFs) are growth factors that mediate epithelial-mesenchymal interactions in various tissues during normal and abnormal processes such as embryo development, wound healing, tissue fibrosis, vascular disorders, and cancer. PDGFs and their receptors (PDGFRs) have emerged as key players in the regulation of embryonic and postnatal development of the male gonad. Cells that express PDGFs and PDGFRs are found in the testis of mammals, birds, and reptiles, and their distribution, regulation, and function vary across species. Testicular PDGFs and PDGFRs appear after the process of sex determination in animals that use either genetic sex determination or environmental sex determination. Sertoli cells are the main PDGF-producing cells during the entire period of prenatal and postnatal testis development. Fetal Leydig cells and their precursors, adult Leydig cells and their stem cell precursors, peritubular myoid cells, cells of the blood vessels, and gonocytes are the testicular cell types expressing PDGFRs. Genetically targeted deletions of PDGFs, PDGFRs, PDGFR target genes or pharmacological silencing of PDGF signaling produce profound damage on the target cells that, depending on the developmental period, are under direct or indirect control of PDGF. PDGF signaling may also serve diverse functions outside of the realm of testis development, including testicular tumors. In this review, we provide a framework of the current knowledge to clarify the useful information regarding how PDGFs function in individual cells of the testis.

Novel compounds with antiangiogenic and antiproliferative potency for growth control of testicular germ cell tumours

BACKGROUND

Testicular germ cell tumour (TGCT) is the most common cause of death from solid tumours in young men and especially for platinum-refractory patients novel treatment approaches are urgently needed. Using an in silico screening approach for the detection of novel cancer drugs with inhibitory effects on the tyrosine kinase activity of growth factors (e.g., VEGFR, PDGFR), we identified two compounds (HP-2 and HP-14) with antiangiogenic and antiproliferative potency, which were evaluated in endothelial cell models and TGCT cells.

RESULTS

HP-2 and HP-14 effectively inhibited the growth of VEGFR-2-expressing TGCT cell lines (Tera-1, Tera-2 and 2102EP) and endothelial cell models, while they failed to supress the growth of VEGFR-2-lacking tumour cells. cDNA-microarrays revealed an inhibition of the expression of several growth factor receptors and related signal transduction molecules. Vascular endothelial growth factor (VEGF)-induced cell migration was also potently inhibited. Cell cycle-regulating proteins such as p21 and p27 were upregulated, leading to an S-phase arrest. Additional in vivo evaluations confirmed the antiangiogenic potency and good tolerability of the novel substances.

CONCLUSION

Our data show that the identified novel compounds inhibit the growth of TGCT cells and decrease angiogenic microvessel formation. The mode of action involves cell cycle arresting effects and changes in the expression pattern of several angiogenic genes. The novel compounds may qualify as new candidates for targeted treatment of TGCT and merit further evaluation.

Chromosomes, genes, and development of testicular germ cell tumors

A literature review found 265 articles on testicular germ cell tumors (TGCTs) detailing the copy number of chromosomal regions and expression of 245 genes. An initial precursor stage, intratubular germ cell neoplasia (IGCN), is characterized by triploidization and an upregulation of KIT, ALPP, CCDN2, and ZNF354A, and a downregulation of CDKN2D. TGCT regularly have a series of chromosomal aberrations: a decrease in copy number at 4q21 approximately qter and 5q14 approximately qter; an increase at 7p21 approximately pter, 7q21 approximately q33, and 8q12 approximately q23 (especially high increase in seminoma); a decrease at 11p11 approximately p15 and 11q14 approximately q24; an increase at 12p11 approximately pter; a decrease at 13q14 approximately q31; an increase of 17q11 approximately q21 (only for nonseminoma); a decrease of 18q12 approximately qter; and an increase at 21q21 approximately qter, 22q11 approximately qter (only for seminoma), and Xq. Macroscopically overt TGCT is associated with a characteristic series of abnormalities in the retinoblastoma pathway including upregulation of cyclin D2 and p27 and downregulation of RB1 and the cyclin-dependent kinase inhibitors p16, p18, p19, and p21. TGCT thus has a synergistic pattern in gene expressions of the retinoblastoma pathway that is rare in other malignancies.

Phenotypic and genotypic alterations characterize patients bearing plasma cell dyscrasias with a high M-component

As at present only a long-term follow-up can fully determine whether monoclonal gammapathies of undetermined significance (MGUS) will evolve into multiple myeloma (MM), this study attempted to identify other variables connected with the amount of monoclonal component (MC), generally considered as the most reliable marker of malignant evolution. Thirty-four MGUS subjects showing a high MC (> or = 15.0 g/l) but without clinical evidence of MM (MGUS group b), were characterized for their phenotypic and genotypic profile by comparing them either with 40 MM patients or with 24 subjects affected by a benign form of monoclonal gammapathy (MGUS group a) according to the standard criteria. In addition to the usual laboratory markers, the levels of expression of a panel of CD membrane subsets were measured on B and T lymphocytes. Also, the serum level of the p53 mutant protein and the structural alterations of the c-myc oncogene were evaluated. The results show that for MGUS group b patients, an increased M-protein was accompanied by significantly increased levels of peripheral blood CD3+ T cells and oncogenetic aberrations in c-myc. Since a high serum MC level seems to indicate a greater likelihood of malignant transformation for MGUS patients, these findings suggest that this relationship may be a result of the concomitant alterations observed at a phenotypic and genotypic level. Such alterations may be potentially useful as surrogate markers for the transition of benign to malignant (MM) plasma cell dyscrasia.

Growth regulatory factors and signalling proteins in testicular germ cell tumours

The molecular basis of testicular germ cell tumourigenesis are not well elucidated. Growth factors regulate cell growth, differentiation and apoptosis. Major families of growth factors are present in the male gonad from early fetal development to adult life. They are involved in germ cell proliferation and differentiation. Growth signalling pathways suffer deregulation in many human malignancies. Given the importance of growth signals in normal testicular development and their acquired deregulation in most human cancers, growth factors and signalling molecules that have been implicated in the genesis of testicular germ cell tumours, are reviewed. We detected a somatic mutation of SMAD4 gene, responsible for loss of protein function in seminomas. This mutational inactivation may affect the activity of several members of TGFbeta superfamily (TGFbeta, activin, inhibin, BMP). VEGF expression has been shown to predict metastasis in seminomas. A significant association of HST-1 expression, a member of fibroblast growth factors, with the nonseminomatous phenotype and with tumour stage has been described. In contrast, C-KIT is expressed by seminomas only, from the preinvasive stage. Despite intense expression in almost all seminomas, activating mutation of C-KIT gene is seldom reported. Recently, the first animal model of classical testicular seminoma has been identified in transgenic mouse overexpressing GDNF. RET (GDNF receptor) expression is demonstrated in human seminomas, and not in nonseminomatous tumours. However, the exact molecular alterations of GDNF/RET/GFRalpha1 complex in germ cell tumours are not known. Finally, beside growth factors, other signalling molecules such as peptide hormones may be involved in testicular carcinogenesis. We have demonstrated a specific pattern of somatostatin receptors expression in each type of testicular germ cell tumours, with a loss of sst3 and sst4 in seminomas and loss of sst4 and expression of sst1 in nonseminomas only. These data suggest an antiproliferative action of somatostatin in testicular cancers. In summary, many growth factors and signalling molecules seem to represent specific markers for different histological types of germ cell tumours (seminomas versus nonseminomas) and may play a role in the differentiation of germ cell tumours. Despite a complex signalling pathway involved in the physiological functions of male gonad, little is known about the implication of this signalling network in testicular malignancies. From a practical stand-point, further studies on the role of growth factors in human germ cell tumours may offer a new therapeutical perspective with the development of specific pharmacological signalling modulators that could be used as therapeutic agents.

Distinct epigenetic phenotypes in seminomatous and nonseminomatous testicular germ cell tumors

The genetic nature of testicular germ cell tumors and the molecular mechanisms underlying the morphological and clinical differences between the two subtypes, seminomas and nonseminomas, remains unclear. Genetic studies show that both subtypes exhibit many of the same regional genomic disruptions, although the frequencies vary and few clear differences are found. We demonstrate significant epigenetic differences between seminomas and nonseminomas by restriction landmark genomic scanning. Seminomas show almost no CpG island methylation, in contrast to nonseminomas that show CpG island methylation at a level similar to other solid tumors. We find an average of 1.11% of CpG islands methylation in nonseminomas, but only 0.08% methylated in seminomas. Furthermore, we demonstrate that seminomas are more highly hypomethylated than nonseminomas throughout their genome. Since both subtypes are thought to arise from primordial germ cells, the epigenetic differences seen between these subtypes may reflect the normal developmental switch in primordial germ cells from an undermethylated genome to a normally methylated genome. We discuss these findings in relation to different developmental models for seminomatous and nonseminomatous testicular germ cell tumors.

PDGF and the testis

Testicular development is controlled by a complex hierarchy of gene regulatory proteins, growth factors, cell adhesion molecules, signaling molecules and hormones that interact, often acting within short time windows, via reciprocal control relationships. The identification in the testis of platelet-derived growth factor (PDGF), a key regulator of connective tissue cells in embryogenesis and pathogenesis, has focused attention on the role of this growth factor in testicular pathophysiology. This review summarizes recent advances in the study of the actions of PDGF in the male gonad, and attempts to incorporate complex in vitro and in vivo experimental data into a model that might clarify the role played by PDGF in the mammalian testis.

Immunohistochemical detection of p53 and p21 proteins in canine testicular tumours

The objective of this study was to detect by immunohistochemical means nuclear accumulations of p53 and p21 proteins in testicular tumours of dogs. Intense p53 protein nuclear labelling was shown by each of seven seminomas and one intermediate collision tumour. Moderate or intense immunoreactivity was shown by three Sertoli cell tumours. All the tumours also showed p21 nuclear reactivity in parallel with the p53 reactivity. In contrast, four Leydig cell tumours showed no detectable immunoreactivity. The results suggested that high levels of p53 accumulation were associated with the expression of wild-type p53, which was able to activate the transcription of the p21 gene. In addition, weak p53- and p21-nuclear reactivities were detectable in primary spermatocytes within normal seminiferous tubules.

Comparison of DNA copy number changes in malignant mesothelioma, adenocarcinoma and large-cell anaplastic carcinoma of the lung

The differential diagnosis of mesothelioma, primary adenocarcinomas and pleural metastases frequently causes problems. We have used the comparative genomic hybridization (CGH) technique on 34 malignant mesotheliomas and 30 primary lung carcinomas (adenocarcinoma, including bronchoalveolar carcinoma and large-cell anaplastic carcinoma) to compare their copy number changes and to evaluate the use of CGH to distinguish between these two types of tumour. In mesothelioma, gains of genetic material occurred as frequently as losses, whereas gains predominated over losses in carcinoma. In mesothelioma, the most frequent changes were losses in 4q, 6q and 14q and gains in 15q and 7p, whereas gains in 8q, 1q, 7p, 5p and 6p were the most common changes in carcinoma. Amplification of KRAS2 was detected in two adenocarcinomas by Southern blot analysis. CGH showed gains in 12p in the same tumours. Statistically significant differences between the two types of tumour were detected in chromosomes X, 1, 2p, 4, 8q, 10q, 12p, 14q, 15q and 18q. When comparing the frequency of gains and losses between mesothelioma and lung carcinoma using discriminant analysis, the sensitivity of CGH to differentiate mesotheliomas from lung carcinomas was 81% and the specificity 77%. The differences in DNA copy number changes between the two types of tumour suggest that they are genetically different tumour entities. Although CGH cannot be used as a definitive discriminatory method, we were able to distinguish between mesothelioma and lung carcinoma in a large proportion of the abnormal cases.

Alterations of the metastasis suppressor gene nm23 and the proto-oncogene c-myc in human testicular germ cell tumors

The putative metastasis suppressor genes nm23-H1, nm23-H2 and the c-myc proto-oncogene were investigated in testicular germ cell tumors (GCTs) using Southern and Northern blotting as well as semiquantitative reverse transcription polymerase chain reaction (RT-PCR) and single strand conformation polymorphism (SSCP) analysis. When studying Bgl II RFLPs, allelic losses of the nm23 gene were found in 3/12 (25%) informative tumors, and all 3 had lymph node and/or distant metastases. A 2 to 7 fold nm23 mRNA overexpression was found in 22/34 (64.7%) tumors examined. RT-PCR revealed that this phenomenon is mainly a consequence of nm23-H2 overexpression. Overexpression of both the H1 and the H2 gene was predominantly found in the seminoma subtype and was not associated with tumor stage. Only 1/25 tumors, a seminoma with distant metastases, had a point mutation in the coding region of the nm23-H2 gene as demonstrated by SSCP analysis. None of the 8 seminomas and only 1/13 non-seminomas had c-myc overexpression. No abnormalities of the c-myc gene could be detected on the DNA level. Despite the fact that in previous investigations nm23-H2 was demonstrated to be a putative transcription factor for c-myc, no coexpression of c-myc and nm23-H2 was found by quantitative RT-PCR in this study.

Germ cell tumors of the testis overexpress wild-type p53

Several recent studies have suggested that testicular germ cell tumors express high levels of wild-type p53 protein. To clarify and confirm this unexpected result, we have investigated seminomatous and nonseminomatous germ cell tumors at the genomic, mRNA, and protein levels. Thirty-five tumors were examined for p53 overexpression using antibodies directed against the p53 (PAb1801, PAb240, and CM1), mdm2 (IF2), and p21Waf1/Clp1 (EA10) proteins. Thirty-two tumors were screened for p53 mutations by single-strand conformation polymorphism analysis. Eighteen tumors were screened with a functional assay that tests the transcriptional competence of human p53 protein expressed in yeast. On frozen sections, 100, 65, 35, 73, and 0% of tumors reacted with the CM1, PAb240, PAb1801, IF2, and EA10 antibodies, respectively. No p53 mutations were detected by single-strand conformation polymorphism or by functional assay. The fact that many tumors overexpress wild-type p53 but not mdm2 rules out mdm2 overexpression as a general explanation for the presence of wild-type p53 in these tumors. The absence of p21 overexpression suggests that p53 may be unable to activate transcription of critical target genes, which may explain why the presence of wild-type p53 is tolerated in this tumor type, although the mechanism for this transcriptional inactivity remains to be established.

Molecular mechanisms of testicular carcinogenesis

Molecular investigations into the neoplastic transformation of a normal spermatogenic precursor cell into a germ-cell malignancy have implicated a wide array of DNA and RNA alterations. Previous epidemiologic and familial patterns of cancer presentation had suggested that testicular cancer developed from one or more genetic alterations. In particular, mutations in cellular oncogenes such as c-kit and tumor-suppressor genes such as the retinoblastoma gene product have been identified as putative etiologic agents in the development and progression of testicular germ-cell tumors. Additionally, alterations in the transcription of RNA that are regulated through a process of genomic imprinting have been identified in human testis cancers. This report provides a framework for integrating this growing literature on the molecular biology of testicular germ-cell tumors into a potential etiologic hypothesis.

Testicular cancer in association with developmental renal anomalies and hypospadias

OBJECTIVES

To characterize the clinical, pathologic, and genetic aspects of patients with a previously undescribed phenotype of testicular germ cell tumors associated with renal hypoplasia or agenesis and urethral hypospadias.

METHODS

Review of clinical and pathologic findings and genetic analysis of constitutional and tumor DNA for mutations of the Wilms' tumor suppressor gene (WT1).

RESULTS

Clinical findings suggest that this phenotype is distinct from other syndromes associated with renal anomalies and that the associated testicular tumors are histologically and clinically similar to those that occur sporadically. No karyotypic abnormalities, loss of heterozygosity, or mutations in the zinc finger domains (exons 7-10) of WT1 were observed in 5 patients with this phenotype.

CONCLUSIONS

The phenotype of testicular germ cell tumor, developmental renal anomalies, and urethral hypospadias constitutes a discrete syndrome caused by a gene distinct from WT1.

Familial occurrence of testicular cancer

The etiology of testicular cancer is unknown. Familial testicular cancer is a rare entity that adds further information to research regarding the genetic influence on germ cell tumors. We report on 5 brothers, including 2 identical triplets and 1 fraternal brother, with testicular cancer and discuss the epidemiological factors. It appears that environmental and genetic factors must be considered.

Chromosome 12 in human testicular cancer: dosage changes and their parental origin

Cytogenetically, a marker chromosome interpreted as i(12p) is present in most testicular tumors of germ cell origin. In this study, 22 patients with testicular germ-cell tumors were investigated by Southern blot hybridization to characterize changes in chromosome 12. In comparison with normal DNA, tumor DNA of 18 patients showed increased dosages of 12p accompanied by a comparable or smaller increase or no change in the dosage of centromeric sequences of chromosome 12. A likely interpretation was that most testicular tumors had one or several isochromosomes for 12p that were formed by somatic division of the centromere and that the points of breakage and reunion in the centromeric region were different in different tumors. Allelic 12p fragments showing increased intensity were paternal in four and maternal in three of seven informative cases. Thus, there was no evidence of sex-limited parental imprinting. Furthermore, the observed patterns of allelic fragments suggested that the marker was an i(12p) formed by sister chromatids of one homolog number 12 rather than the result of interchange of genetic material between different homologues.