Towards a non-invasive method for early detection of testicular neoplasia in semen samples by identification of fetal germ cell-specific markers

Beyond liquid biopsy: Toward non-invasive assays for distanced cancer diagnostics in pandemics

Liquid biopsy technologies have seen a significant improvement in the last decade, offering the possibility of reliable analysis and diagnosis from several biological fluids. The use of these technologies can overcome the limits of standard clinical methods, related to invasiveness and poor patient compliance. Along with this there are now mature examples of lab-on-chips (LOC) which are available and could be an emerging and breakthrough technology for the present and near-future clinical demands that provide sample treatment, reagent addition and analysis in a sample-in/answer-out approach. The possibility of combining non-invasive liquid biopsy and LOC technologies could greatly assist in the current need for minimizing exposure and transmission risks. The recent and ongoing pandemic outbreak of SARS-CoV-2, indeed, has heavily influenced all aspects of life worldwide. Ordinary tasks have been forced to switch from “in presence” to “distanced”, limiting the possibilities for a large number of activities in all fields of life outside of the home. Unfortunately, one of the settings in which physical distancing has assumed noteworthy consequences is the screening, diagnosis and follow-up of diseases.

In this review, we analyse biological fluids that are easily collected without the intervention of specialized personnel and the possibility that they may be used -or not-for innovative diagnostic assays. We consider their advantages and limitations, mainly due to stability and storage and their integration into Point-of-Care diagnostics, demonstrating that technologies in some cases are mature enough to meet current clinical needs.

Seminal levels of angiotensin II and angiotensin II type 2 receptor expression on spermatozoa in varicocele patients: Relation to fertility status

Several theories were proposed to explain the pathophysiology of varicocele-related infertility seen in some patients. Our aim was to study the levels of angiotensin II in semen and angiotensin II type 2 receptor expression on spermatozoa in varicocele patients in relation to their fertility status and to evaluate the influence of varicocelectomy on their levels in infertile varicocele patients. Thirty fertile and 30 infertile varicocele patients and 30 healthy controls were subjected to measurement of reproductive hormones, semen analysis, measurement of seminal angiotensin II and evaluation of angiotensin II type 2 receptor expression on spermatozoa. Infertile varicocele patients underwent varicocelectomy and were re-evaluated for the same parameters after the operation. Sperm concentration, morphology, progressive motility, seminal angiotensin II and angiotensin II type 2 receptor expression were significantly lower in infertile varicocele patients compared with the other groups. Post-operative values showed significant increase in the studied parameters compared with the pre-operative values but not to other two groups. A significant positive correlation between angiotensin II type 2 receptor expression and progressive motility was detected in all studied groups. In conclusion, dysregulation of angiotensin II and angiotensin II type 2 receptor in varicocele patients may be involved in varicocele-related infertility.

On the Origin of Testicular Germ Cell Tumors: From Gonocytes to Testicular Cancer

Human primordial germ cells (PGCs) have been described in the yolk sac wall around the beginning of the third week. From week 4 to 5, they migrate under control of SCF/c-KIT signaling pathway to the genital ridge, where they become gonocytes. PGCs and gonocytes express classic pluripotency markers, such as KIT, NANOG, and OCT3/4 that, during spermatogonia differentiation, are gradually suppressed, and substituted by the expression of some germ cell specific genes, such as VASA, SOX17, and TSPY. These genes, during normal development of germ cells, are tightly regulated by epigenetic modification, in terms of microRNA expression and DNA methylation. In adolescents and young adults, testicular germ cell tumors (TGCT) have a common precursor, the germ cell neoplasia in situ (GCNIS); the hypothesis of their origin from PGCs or gonocytes, whose maturation is altered, is widely accepted. The origin of TGCT, probably starting at early stages of embryogenesis, seems to be a part of the Testicular Dysgenesis Syndrome (TDS) where some early PGC/gonocytes, for still unclear reasons, are blocked in their differentiation, retaining their early marker profile. In this paper, current knowledge on the combination of epidemiological and genomic factors, involved in the development of testicular germ cell tumors, is reviewed.

Can germ cell neoplasia in situ be diagnosed by measuring serum levels of microRNA371a-3p?

Purpose

Diagnosing germ cell neoplasia in situ (GCNis) can detect germ cell tumours (GCTs) at the pre-invasive stage. To date, testicular biopsy with the potential of surgical complications is the only way of safely diagnosing GCNis. Recently, microRNAs (miRs) 371-3, and miR 367 were shown to be valuable serum biomarkers of GCTs. We explored the usefulness of these candidate miRs as a marker for GCNis.

Methods

27 patients with GCNis and no concomitant GCT were enrolled. All patients underwent measuring serum levels of miR-371a-3p and miR-367-3p before treatment, 11 had repeat measurement after treatment, 2 also had testicular vein blood examinations. Serum levels were measured by quantitative PCR. In addition, four orchiectomy specimens of patients with GCT were examined immunohistochemically and by in situ hybridization (ISH) with a probe specific for miR-371a-3p to look for the presence of this miR in GCNis cells.

Results

The median serum level of miR-371a-3p was significantly higher in patients with GCNis than in controls, miR-367 levels were not elevated. Overall, 14 patients (51.9%) had elevated serum levels of miR-371a-3p. The highest levels were found in patients with bilateral GCNis. Levels in testicular vein serum were elevated in both of the cases. After treatment, all elevated levels dropped to normal. In two orchiectomy specimens, miR-371a-3p was detected by ISH in GCNis cells.

Conclusions

Measuring miR-371a-3p serum levels can replace control biopsies after treatment of GCNis. In addition, the test can guide clinical decision making regarding the need of testicular biopsy in cases suspicious of GCNis.

The genomic landscape of testicular germ cell tumours: from susceptibility to treatment

The genomic landscape of testicular germ cell tumour (TGCT) can be summarized using four overarching hypotheses. Firstly, TGCT risk is dominated by inherited genetic factors, which determine nearly half of all disease risk and are highly polygenic in nature. Secondly KIT-KITLG signalling is currently the major pathway that is implicated in TGCT formation, both as a predisposition risk factor and a somatic driver event. Results from genome-wide association studies have also consistently suggested that other closely related pathways involved in male germ cell development and sex determination are associated with TGCT risk. Thirdly, the method of disease formation is unique, with tumours universally stemming from a noninvasive precursor lesion, probably of fetal origin, which lies dormant through childhood into adolescence and then eventually begins malignant growth in early adulthood. Formation of a 12p isochromosome, a hallmark of TGCT observed in nearly all tumours, is likely to be a key triggering event for malignant transformation. Finally, TGCT have been shown to have a distinctive somatic mutational profile, with a low rate of point mutations contrasted with frequent large-scale chromosomal gains. These four hypotheses by no means constitute a complete model that explains TGCT tumorigenesis, but advances in genomic technologies have enabled considerable progress in describing and understanding the disease. Further advancing our understanding of the genomic basis of TGCT offers a clear opportunity for clinical benefit in terms of preventing invasive cancer arising in young men, decreasing the burden of chemotherapy-related survivorship issues and reducing mortality in the minority of patients who have treatment-refractory disease.

Etiology and early pathogenesis of malignant testicular germ cell tumors: towards possibilities for preinvasive diagnosis

Malignant testicular germ cell tumors (TGCT) are the most frequent cancers in Caucasian males (20-40 years) with an 70% increasing incidence the last 20 years, probably due to combined action of (epi)genetic and (micro)environmental factors. It is expected that TGCT have carcinoma in situ(CIS) as their common precursor, originating from an embryonic germ cell blocked in its maturation process. The overall cure rate of TGCT is more than 90%, however, men surviving TGCT can present long-term side effects of systemic cancer treatment. In contrast, men diagnosed and treated for CIS only continue to live without these long-term side effects. Therefore, early detection of CIS has great health benefits, which will require an informative screening method. This review described the etiology and early pathogenesis of TGCT, as well as the possibilities of early detection and future potential of screening men at risk for TGCT. For screening, a well-defined risk profile based on both genetic and environmental risk factors is needed. Since 2009, several genome wide association studies (GWAS) have been published, reporting on single-nucleotide polymorphisms (SNPs) with significant associations in or near the genes KITLG, SPRY4, BAK1, DMRT1, TERT, ATF7IP, HPGDS, MAD1L1, RFWD3, TEX14, and PPM1E, likely to be related to TGCT development. Prenatal, perinatal, and postnatal environmental factors also influence the onset of CIS. A noninvasive early detection method for CIS would be highly beneficial in a clinical setting, for which specific miRNA detection in semen seems to be very promising. Further research is needed to develop a well-defined TGCT risk profile, based on gene-environment interactions, combined with noninvasive detection method for CIS.

Polygenic susceptibility to testicular cancer: implications for personalised health care

BACKGROUND

The increasing incidence of testicular germ cell tumour (TGCT) combined with its strong heritable basis suggests that stratified screening for the early detection of TGCT may be clinically useful. We modelled the efficiency of such a personalised screening approach, based on genetic risk profiling in combination with other diagnostic tools.

METHODS

We compared the number of cases potentially detectable in the population under a number of screening models. The polygenic risk scoring (PRS) model was assumed to have a log-normal relative risk distribution across the 19 currently known TGCT susceptibility variants. The diagnostic performance of testicular biopsy and non-invasive semen analysis was also assessed, within a simulated combined screening programme.

RESULTS

The area under the curve for the TGCT PRS model was 0.72 with individuals in the top 1% of the PRS having a nine-fold increased TGCT risk compared with the population median. Results from population-screening simulations only achieved a maximal positive predictive value (PPV) of 60%, highlighting broader clinical factors that challenge such strategies, not least the rare nature of TGCT. In terms of future improvements, heritability estimates suggest that a significant number of additional genetic risk factors for TGCT remain to be discovered, identification of which would potentially yield improvement of the PPV to 80-90%.

CONCLUSIONS

While personalised screening models may offer enhanced TGCT risk discrimination, presently the case for population-level testing is not compelling. However, future advances, such as more routine generation of whole genome data is likely to alter the landscape. More targeted screening programs may plausibly then offer clinical benefit, particularly given the significant survivorship issues associated with the successful treatment of TGCT.

Analysis of POU5F1, c-Kit, PLAP, AP2γ and SALL4 in gonocytes of patients with cryptorchidism

Cryptorchidism is a risk factor for the development of testicular germ cell tumors (TGCTs). The most common type of TGCT in cryptorchidism is seminoma. The intratubular germ cell neoplasia unclassified (ITGCNU) is a histological pattern preceding the development of seminomas and non-seminomas. It was suggested that in patients with cryptorchidism, the gonocytes remained undifferentiated with pluripotent abilities expressing proteins like POU domain class 5 transcription factor 1 (POU5F1), tyrosine kinase receptor c-Kit, placental-like alkaline phosphatase (PLAP), the transcription factor AP2γ and sal-like protein 4 (SALL4) that confer to the gonocytes this ability and therefore make them susceptible to develop ITGCNU. The aim of the present study was to determine if the gonocytes of patients with cryptorchidism express POU5F1, c-Kit, PLAP, AP2γ and SALL4 proteins after their differentiation period. Based on this, we evaluated samples of testicular tissue from newborns to 16-year old subjects with or without cryptorchidism in search of POU5F1, c-Kit, PLAP, AP2γ and SALL4 using immunocytochemical method, the results of which were validated by RT-PCR. The results showed that control subjects witnessed a down-regulation in the expression of these five proteins in the first year of life, which eventually disappeared. On the other hand, it was determined that 21.6% (8/37) of the patients with cryptorchidism continued to express, at least, one of the proteins analyzed in this study after the second year of life. And only 5.4% (2/37) of the patients were positive to the five markers. These data sustain the proposed hypothesis that in cryptorchid patients, ITGCNU arises from gonocytes that fail in their differentiation process to spermatogonia with conservation of the proteins (POU5F1, c-Kit, PLAP, AP2γ and SALL4) that maintain pluripotency and undifferentiated characteristics and which are responsible for making the gonocytes susceptible to malignancy. However, we cannot guarantee that these patients present neoplastic transformation.

An oncofetal and developmental perspective on testicular germ cell cancer

Germ cell tumors (GCTs) represent a diverse group of tumors presumably originating from (early fetal) developing germ cells. Most frequent are the testicular germ cell cancers (TGCC). Overall, TGCC is the most frequent malignancy in Caucasian males (20-40 years) and remains an important cause of (treatment related) mortality in these young men. The strong association between the phenotype of TGCC stem cell components and their totipotent ancestor (fetal primordial germ cell or gonocyte) makes these tumors highly relevant from an onco-fetal point of view. This review subsequently discusses the evidence for the early embryonic origin of TGCCs, followed by an overview of the crucial association between TGCC pathogenesis, genetics, environmental exposure and the (fetal) testicular micro-environment (genvironment). This culminates in an evaluation of three genvironmentally modulated hallmarks of TGCC directly related to the oncofetal pathogenesis of TGCC: (1) maintenance of pluripotency, (2) cell cycle control/cisplatin sensitivity and (3) regulation of proliferation/migration/apoptosis by KIT-KITL mediated receptor tyrosine kinase signaling. Briefly, TGCC exhibit identifiable stem cell components (seminoma and embryonal carcinoma) and progenitors that show large and consistent similarities to primordial/embryonic germ cells, their presumed totipotent cells of origin. TGCC pathogenesis depends crucially on a complex interaction of genetic and (micro-)environmental, i.e. genvironmental risk factors that have only been partly elucidated despite significant effort. TGCC stem cell components also show a high degree of similarity with embryonic stem/germ cells (ES) in the regulation of pluripotency and cell cycle control, directly related to their exquisite sensitivity to DNA damaging agents (e.g. cisplatin). Of note, (ES specific) micro-RNAs play a pivotal role in the crossover between cell cycle control, pluripotency and chemosensitivity. Moreover, multiple consistent observations reported TGCC to be associated with KIT-KITL mediated receptor tyrosine kinase signaling, a pathway crucially implicated in proliferation, migration and survival during embryogenesis including germ cell development. In conclusion, TGCCs are a fascinating model for onco-fetal developmental processes especially with regard to studying cell cycle control, pluripotency maintenance and KIT-KITL signaling. The knowledge presented here contributes to better understanding of the molecular characteristics of TGCC pathogenesis, translating to identification of at risk individuals and enhanced quality of care for TGCC patients (diagnosis, treatment and follow-up).

Human Melanoma cells over-express extracellular matrix 1 (ECM1) which is regulated by TFAP2C

Extracellular matrix 1 (ECM1) is over-expressed in multiple epithelial malignancies. However, knowledge regarding the expression of ECM1 in melanomas and the mechanisms of ECM1 regulation is limited. In this study, we found that ECM1 is over-expressed in several melanoma cell lines, when compared to primary melanocytes, and furthermore, that ECM1 expression paralleled that of TFAP2C levels in multiple cell lines. Knockdown of TFAP2C in the A375 cell line with siRNA led to a reduction in ECM1 expression, and upregulation of TFAP2C with adenoviral vectors in the WM793 cell line resulted in ECM1 upregulation. Utilizing 5’ RACE to identify transcription start sites (TSS) and luciferase reporter assays in the ECM1-overexpressing A375 cell line, we identified the minimal promoter region of human ECM1 and demonstrate that an approximately 100bp fragment upstream of the TSS containing a TATA box and binding sites for AP1, SP1 and Ets is sufficient for promoter activity. Chromatin immunoprecipitation and direct sequencing (ChIP-seq) for TFAP2C in the A375 cell line identified an AP2 regulatory region in the promoter of the ECM1 gene. Gelshift assays further confirmed binding of TFAP2C to this site. ECM1 knockdown reduces melanoma cell attachment and is consistent with findings that ECM1 overexpression has been associated with a poor prognosis. Our investigations show an as yet unrecognized role for TFAP2C in melanoma via its regulation of ECM1.

Curcumin inhibits AP-2γ-induced apoptosis in the human malignant testicular germ cells in vitro

AIM

To investigate the effects of curcumin on proliferation and apoptosis in testicular cancer cells in vitro and to investigate its molecular mechanisms of action.

METHODS

NTera-2 human malignant testicular germ cell line and F9 mouse teratocarcinoma stem cell line were used. The anti-proliferative effect was examined using MTT and colony formation assays. Hoechst 33258 staining, TUNEL and Annexin V-FITC/PI staining assays were used to analyze cell apoptosis. Protein expression was examined with Western blot analysis and immunocytochemical staining.

RESULTS

Curcumin (5, 10 and 15 μmol/L) inhibited the viability of NTera-2 cells in dose- and time-dependent manners. Curcumin significantly inhibited the colony formation in both NTera-2 and F9 cells. Curcumin dose-dependently induced apoptosis of NTera-2 cells by reducing FasL expression and Bcl-2-to-Bax ratio, and activating caspase-9, -8 and -3. Furthermore, curcumin dose-dependently reduced the expression of AP transcription factor AP-2γ in NTera-2 cells, whereas the pretreatment with the proteasome inhibitor MG132 blocked both the curcumin-induced reduction of AP-2γ and antiproliferative effect. Curcumin inhibited ErbB2 expression, and decreased the phosphorylation of Akt and ERK in NTera-2 cells.

CONCLUSION

Curcumin induces apoptosis and inhibits proliferation in NTera-2 cells via the inhibition of AP-2γ-mediated downstream cell survival signaling pathways.

MicroRNA expression profiling of carcinoma in situ cells of the testis

Testicular germ cell tumours, seminoma (SE) and non-seminoma (NS), of young adult men develop from a precursor cell, carcinoma in situ (CIS), which resembles foetal gonocytes and retains embryonic pluripotency. We used microarrays to analyse microRNA (miRNA) expression in 12 human testis samples with CIS cells and compared it with miRNA expression profiles of normal adult testis, testis with Sertoli-cell-only that lacks germ cells, testis tumours (SE and embryonal carcinoma (EC), an undifferentiated component of NS) and foetal male and female gonads. Principal components analysis revealed distinct miRNA expression profiles characteristic for each of the different tissue types. We identified several miRNAs that were unique to testis with CIS cells, foetal gonads and testis tumours. These included miRNAs from the hsa-miR-371-373 and -302-367 clusters that have previously been reported in germ cell tumours and three miRNAs (hsa-miR-96, -141 and -200c) that were also expressed in human epididymis. We found several miRNAs that were upregulated in testis tumours: hsa-miR-9, -105 and -182-183-96 clusters were highly expressed in SE, while the hsa-miR-515-526 cluster was high in EC. We conclude that the miRNA expression profile changes during testis development and that the miRNA profile of adult testis with CIS cells shares characteristic similarities with the expression in foetal gonocytes.

A pathologist's view on the testis biopsy

Aspects of the biopsy of the testis from the pathologist's point of view are discussed. Direct enzyme-histochemical staining for alkaline phosphatase (dAP) on frozen sections of biopsies taken during operation is a useful diagnostic tool to aid surgeons in testis-sparing surgery. Biopsy of the contralateral testis for the diagnosis of carcinoma in situ (CIS) in patients with a testicular germ cell tumour is not standard of care in most countries because of the high rate of negative biopsies. Based on risk factors for germ cell tumours, i.p. microlithiasis, a patient population is defined in which the rate of CIS in the contralateral biopsy is about 25%. It is reiterated that the diagnosis of CIS in testicular biopsies requires expertise, and should not be carried out without immunohistochemistry for markers for CIS. As OCT3/4 is increasingly used as marker, it is important to be aware that it may be false-negative in biopsies fixed in Bouin's or Stieve's fixative. Preliminary results are presented on a series of biopsies from cryptorchid testes in infants and children allowing the definition of morphological and immunohistochemical criteria for delayed maturation of gonocytes and pre-CIS.

Ultrastructural evaluation of semen to assess effects of exposure to toxicants

Conventional light microscopic evaluation of a semen ejaculate does not fully utilize potential indicators of functional impairment in sperm organelles. The technique described here facilitates critical evaluation of morphological features of spermatozoal organelles at an ultrastructural level and helps identify vulnerable targets. Compared with a battery of sperm function assays employed in andrology clinics, this relatively less expensive technique efficiently uses semen as biopsy material and thus serves as a comprehensive means to assess the impact of toxicants on the male reproductive system.

The role of BLIMP1 and its putative downstream target TFAP2C in germ cell development and germ cell tumours

During the past years, much information has been gathered regarding the genetic and epigenetic programmes leading to the specification and maintenance of primordial germ cells. Expression of the transcriptional regulator BLIMP1 (PRDM1) is regarded as the main event in germ cell specification. BLIMP1 induces a set of target genes, one of them being transcription factor TFAP2C (AP-2γ, Tcfap2c). In murine loss of function models Blimp1 and Tcfap2c share an identical phenotype, strengthening the assumption that they act in the same pathway. One major role of this pathway is the inhibition of somatic differentiation in germ cells. BLIMP1 and TFAP2C are also expressed in carcinoma in situ (CIS, IGCNU, TIN) and in seminoma. As pointed out herein, the presence of both proteins helps to explain the undifferentiated nature of these germ cell tumours. In addition, we performed a meta-analysis of high-throughput datasets searching for TFAP2C/Tcfap2c target genes. This analysis leads us to suggest Nanos3, Dmrt1 and Dnmt3b as potential TFAP2C/Tcfap2c target genes with relevance to germ cell development and germ cell tumours.

A novel double staining strategy for improved detection of testicular carcinoma in situ cells in human semen samples

Prompted by the recently reported expression of POU5F1 (OCT3/4) in epididymis, a panel of markers for carcinoma in situ (CIS) testis and testicular germ cell tumours (TGCT), including AP-2γ(TFAP2C), NANOG, OCT3/4, KIT, placental-like alkaline phosphatase (PLAP), M2A/PDPN and MAGE-A4 were examined by immunohistochemistry or in situ hybridisation in urogenital epithelia, which may interfere with detection of CIS cells in semen. In addition to OCT3/4, the expression of AP-2γ and NANOG or their variants was detected in urogenital epithelia, while other CIS markers, including PLAP/alkaline phosphatase were absent. A combination of immunocytological staining for AP-2γ or OCT3/4 and rapid cytochemical alkaline phosphatase reaction was subsequently developed. This approach was tested in 22 patients with TGCT. In 14 patients (63.6%), double stained cells were found and thus the method was proven suitable for the detection of CIS cells in semen. In conclusion, transcription factors related to pluripotency and undifferentiated state of cells, which most likely have several variants or modifications, are unexpectedly detected using currently available antibodies in urogenital epithelial cells which may be shed into semen. Combining the immunohistochemical nuclear markers with a rapid cytochemical alkaline phosphatase reaction for detection of CIS cells in ejaculates may provide a more reliable diagnostic method.

Human testicular (non)seminomatous germ cell tumours: the clinical implications of recent pathobiological insights

Human germ cell tumours (GCTs) comprise several types of neoplasias with different pathogeneses and clinical behaviours. A classification into five subtypes has been proposed. Here, the so-called type II testicular GCTs (TGCTs), ie the seminomas and non-seminomas, will be reviewed with emphasis on pathogenesis and clinical implications. Various risk factors have been identified that define subpopulations of men who are amenable to early diagnosis. TGCTs are omnipotent, able to generate all differentiation lineages, both embryonic and extra-embryonic, as well as the germ cell lineage itself. The precursor lesion, composed of primordial germ cells/gonocytes, is referred to as carcinoma in situ of the testis (CIS) and gonadoblastoma of the dysgenetic gonad. These pre-malignant cells retain embryonic characteristics, which probably explains the unique responsiveness of the derived tumours to DNA-damaging agents. Development of CIS and gonadoblastoma is crucially dependent on the micro-environment created by Sertoli cells in the testis, and granulosa cells in the dysgenetic gonad. OCT3/4 has high sensitivity and specificity for CIS/gonadoblastoma, seminoma, and embryonal carcinoma, and is useful for the detection of CIS cells in semen, thus a promising tool for non-invasive screening. Overdiagnosis of CIS due to germ cell maturation delay can be avoided using immunohistochemical detection of stem cell factor (SCF). Immunohistochemistry is helpful in making the distinction between seminoma and embryonal carcinoma, especially SOX17 and SOX2. The different non-seminomatous histological elements can be recognized using various markers, such as AFP and hCG, while others need confirmation. The value of micro-satellite instability as well as BRAF mutations in predicting treatment resistance needs validation in prospective trials. The availability of representative cell lines, both for seminoma and for embryonal carcinoma, allows mechanistic studies into the initiation and progression of this disease.

Seminal expression of NY-ESO-1 and MAGE-A4 as markers for the testicular cancer

Testicular germ cell tumours (TGCTs) are the most common malignancies in Caucasian young men and their incidence has increased over the past decades. However, a non-invasive test allowing an early diagnosis of TGCT often proves inaccurate. We have previously shown that two Cancer-Testis Antigens (CTA), namely MAGE-A4 and NY-ESO-1, were expressed by TGCT. As exfoliation of carcinoma in situ (CIS) cells or tumour germ cells from testis into seminal fluid can occur, here we studied the expression of the 2 CTA in semen smears of patients with testicular cancer in comparison with healthy men. Using semen smears from healthy controls (n = 65) and patients diagnosed for testicular tumour (n = 57) and immunological staining, we observed expression of MAGE-A4 and NY-ESO-1 proteins in seminal fluid exfoliated cells. We found a highly statistically significant difference in the ratios of stained cells to the total number of round cells between testicular cancer patients and healthy controls. Multivariable analysis, including sperm parameters and immunostaining on sperm smears, shows the improvement. This technique can provide towards testicular cancer diagnosis when it is included in the current testing regime. However, the fact that expression of these markers was not restricted to foetal germ cells led to detection in the semen of a number of healthy subjects. Although the detection of these CTA could be useful to characterize the sub-type of individual TGCTs better, we stress here that the false positive rate precludes the exclusive employment of these CTA for the early detection of testicular neoplasia.

Origin of pluripotent germ cell tumours: the role of microenvironment during embryonic development

Carcinoma in situ (CIS) testis, known also as intratubular germ cell neoplasia, is the cancer stem cell from which the great majority of testicular germ cell derived tumours (TGCTs) of the testis arise. TGCTs can proliferate into morphologically homogeneous seminomas or can differentiate into virtually any type of tissue and form teratomas (non-seminomas). CIS cells display a close phenotypic similarity to fetal germ cells (primordial germ cells or gonocytes) suggesting an origin due to a developmental delay or arrest of differentiation of early germ cells. The pluripotency of these neoplasms has recently been explained by a close resemblance of their expression profile to that of embryonic inner cell mass cells studied in culture as embryonic stem cells, with high expression of transcription factors associated with pluripotency, such as NANOG and OCT3/4, as well as proteins found in several tissue specific stem cells, such as TFAP2C (AP-2gamma) or KIT. CIS and seminomas highly express a number of pre-meiotic germ cell specific genes, which are down-regulated during development to non-seminomas, while the expression of other embryonic markers, such as SOX2, is up-regulated. The mechanistic pathways and causative factors remain to be elucidated of both the initial transformation of fetal germ cells into CIS cells and the progression of CIS cells into an invasive tumour in the young adult. However, evidence supported by epidemiological studies indicate that disturbances in the hormonal microenvironment of the differentiating gonads may results in both the neoplasia and a host of other problems later in life, such as genital malformations, decreased spermatogenesis, and signs of hypogonadism.

Application of stem cell markers in search for neoplastic germ cells in dysgenetic gonads, extragonadal tumours, and in semen of infertile men

Germ cell tumours (GCTs) are a complex entity. Current areas of attention include early detection and avoidance of unnecessary over-treatment. Novel findings regarding diagnosis of GCTs located in various anatomical sites are described, particularly testicular GCTs and their common progenitor, carcinoma in situ (CIS). Recognition of CIS enables intervention before tumour development, but nevertheless, testicular GCTs are sporadically diagnosed at the pre-invasive stage where minimal treatment is necessary. As presence of CIS is asymptomatic, a simple screening method is needed when CIS is suspected (i.e. in males investigated for infertility). To develop approaches for early detection CIS gene expression studies have been performed showing many similarities with embryonic stem cells with confirmation of established markers (i.e. PLAP, OCT-3/4, KIT) and identification of novel markers (i.e. AP-2 gamma, NANOG). We have reported a very promising new approach of AP-2 gamma (or OCT3/4) based immunocytological semen analysis (specificity 93.6%, sensitivity 54.5%). Comparative studies of gonadal/extragonadal GCTs have revealed resemblance pointing towards similar, but not identical, origins. Moreover, infertility and testicular cancer are connected in the 'Testicular Dysgenesis Syndrome' and 25% of contralateral testes from testicular GCT patients harbour dysgenetic features, including impaired spermatogenesis. Thus, recent data have provided potential diagnostic tools including CIS detection in semen, microarray-based tumour classification, additional serological GCT markers, and novel stem cell markers for immunohistochemical diagnosis of gonadal and extragonadal GCTs. Many CIS candidate genes are yet uninvestigated, and information from these could increase knowledge about CIS tumour initiation/progression and be used for optimisation of a non-invasive detection method.

The epigenome of testicular germ cell tumors

Gene expression is tightly regulated in normal cells, and epigenetic changes disturbing this regulation are a common mechanism in the development of cancer. Testicular germ cell tumor (TGCT) is the most common malignancy among young males and can be classified into two main histological subgroups: seminomas, which are basically devoid of DNA methylation, and nonseminomas, which in general have methylation levels comparable with other tumor tissues, as shown by restriction landmark genome scanning (RLGS). In general, DNA methylation seems to increase with differentiation, and among the nonseminomas, the pluripotent and undifferentiated embryonal carcinomas harbor the lowest levels of DNA promoter hypermethylation, whereas the well-differentiated teratomas display the highest. In this regard, TGCTs resemble the early embryogenesis. So far, only a limited number of tumor suppressor genes have been shown to be inactivated by DNA promoter hypermethylation in more than a minor percentage of TGCTs, including MGMT, SCGB3A1, RASSF1A, HIC1, and PRSS21. In addition, imprinting defects, DNA hypomethylation of testis/cancer associated genes, and the presence of unmethylated XIST are frequent in TGCTs. Aberrant DNA methylation has the potential to improve current diagnostics by noninvasive testing and might also serve as a prognostic marker for treatment response.

Current approaches for detection of carcinoma in situ testis

Testicular germ cell tumours have a favourable prognosis if detected early, but are potentially lethal in a subset of patients. Multi-modality treatment is often necessary, thus the preferable time of diagnosis is at the pre-invasive, but unfortunately often asymptomatic precursor stage of carcinoma in situ (CIS). This review describes current possible approaches for the detection of CIS. At present, an open testicular biopsy is the only definitive way of establishing the presence of CIS. The tissue section should be of an adequate size, be properly fixed, and evaluation be supported by at least one solid immunohistochemical marker, for example PLAP, OCT-3/4 or AP-2gamma. Determination of who should be offered testicular biopsies is based on clinical and ultrasonic examination along with the evaluation of risk factors. A surgical biopsy is an invasive procedure with potential complications, although rare. Therefore, a noninvasive and equally reliable method is needed. Testicular ultrasound is risk-free, painless and at present the only noninvasive method of aid for andrologists when CIS is suspected. The presence of testicular microlithiasis is, in some cases, indicative of pre-malignant changes, especially in males with additional risk factors. Promising results have recently been obtained with a novel noninvasive detection method based on immunocytological AP-2gamma-staining of CIS cells in semen. This method could be a supporting method in andrology centres where careful follow-up is possible. In conclusion, one difficulty is to determine in which males CIS should be suspected; secondly, there does not as yet exist an optimal noninvasive method of diagnosis that is more acceptable than an open surgical biopsy.