The human Y-encoded testis-specific protein interacts functionally with eukaryotic translation elongation factor eEF1A, a putative oncoprotein

Circum-Mediterranean influence in the Y-chromosome lineages associated with prostate cancer in Mexican men: A Converso heritage founder effect?

Prostate cancer is the second most common neoplasia amongst men worldwide. Hereditary susceptibility and ancestral heritage are well-established risk factors that explain the disparity trends across different ethnicities, populations, and regions even within the same country. The Y-chromosome has been considered a prototype biomarker for male health. African, European, Middle Eastern, and Hispanic ancestries exhibit the highest incidences of such neoplasia; Asians have the lowest rates. Nonetheless, the contribution of ancestry patterns has been scarcely explored among Latino males. The Mexican population has an extremely diverse genetic architecture where all the aforementioned ancestral backgrounds converge. Trans-ethnic research could illuminate the aetiology of prostate cancer, involving the migratory patterns, founder effects, and the ethnic contributions to its disparate incidence rates. The contribution of the ancestral heritage to prostate cancer risk were explored through a case-control study (152 cases and 372 controls) study in Mexican Mestizo males. Seventeen microsatellites were used to trace back the ancestral heritage using two Bayesian predictor methods. The lineage R1a seems to contribute to prostate cancer (ORadjusted:8.04, 95%CI:1.41-45.80) development, whereas E1b1a/E1b1b and GHIJ contributed to well-differentiated (Gleason ≤ 7), and late-onset prostate cancer. Meta-analyses reinforced our findings. The mentioned lineages exhibited a connection with the Middle Eastern and North African populations that enriched the patrilineal diversity to the southeast region of the Iberian Peninsula. This ancestral legacy arrived at the New World with the Spanish and Sephardim migrations. Our findings reinforced the contribution of family history and ethnic background to prostate cancer risk, although should be confirmed using a large sample size. Nonetheless, given its complex aetiology, in addition to the genetic component, the lifestyle and xenobiotic exposition could also influence the obtained results.

The eEF1A protein in cancer: Clinical significance, oncogenic mechanisms, and targeted therapeutic strategies

Eukaryotic elongation factor 1A (eEF1A) is among the most abundant proteins in eukaryotic cells. Evolutionarily conserved across species, eEF1A is in charge of translation elongation for protein biosynthesis as well as a plethora of non-translational moonlighting functions for cellular homeostasis. In malignant cells, however, eEF1A becomes a pleiotropic driver of cancer progression via a broad diversity of pathways, which are not limited to hyperactive translational output. In the past decades, mounting studies have demonstrated the causal link between eEF1A and carcinogenesis, gaining deeper insights into its multifaceted mechanisms and corroborating its value as a prognostic marker in various cancers. On the other hand, an increasing number of natural and synthetic compounds were discovered as anticancer eEF1A-targeting inhibitors. Among them, plitidepsin was approved for the treatment of multiple myeloma whereas metarrestin was currently under clinical development. Despite significant achievements in these two interrelated fields, hitherto there lacks a systematic examination of the eEF1A protein in the context of cancer research. Therefore, the present work aims to delineate its clinical implications, molecular oncogenic mechanisms, and targeted therapeutic strategies as reflected in the ever expanding body of literature, so as to deepen mechanistic understanding of eEF1A-involved tumorigenesis and inspire the development of eEF1A-targeted chemotherapeutics and biologics.

High-throughput proteomic characterization of seminal plasma from bulls with contrasting semen quality

Seminal plasma proteins are the major extrinsic factors that can modulate the sperm quality and functions. The present study was carried out to compare the proteomic profiles of seminal plasma from breeding bulls producing good and poor quality semen in an effort to understand the possible proteins associated with semen quality. A total of 910 and 715 proteins were detected in the seminal plasma of poor and good quality semen producing bulls, respectively. A total of 705 proteins were common to both the groups, in which 380 proteins were upregulated and 89 proteins were downregulated in the seminal plasma of poor quality semen, while 236 proteins were co-expressed. The proteins negatively influencing sperm functions such as CCL2, UQCRC2, and SAA1 were among the top ten upregulated proteins in the seminal plasma of poor quality semen. Proteins having a positive role in sperm functions (NGF, EEF1A2, COL1A2, IZUMO4, PRSS1, COL1A1, WFDC2) were among the top ten downregulated proteins in the seminal plasma of poor quality semen. The upregulation of oxidation-reduction process-related proteins, histone proteins (HIST3H2A, H2AFJ, H2AFZ, H2AFX, HIST2H2AB, H2AFV, HIST1H2AC, HIST2H2AC, LOC104975684, LOC524236, LOC614970, LOC529277), and ubiquinol-cytochrome-c reductase proteins (UQCRB, UQCRFS1, UQCRQ, UQCRC1, UQCRC2) indicate deranged oxidation-reduction equilibrium, chromatin condensation and spermatogenesis in poor quality semen producing bulls. The expression of proteins essential for motile cilium (CCDC114, CFAP206, TEKT4), chromatin integrity (PRM2), gamete fusion (IZUMO4, EQTN), hyperactivation, tyrosine phosphorylation, and capacitation [PI3K-Akt signalling pathway-related proteins (COL1A1, COL2A1, COL1A2, SPP1, PDGFA, NGF)] were down regulated in poor quality semen producing bulls.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-023-03474-6.

Y chromosome is moving out of sex determination shadow

Although sex hormones play a key role in sex differences in susceptibility, severity, outcomes, and response to therapy of different diseases, sex chromosomes are also increasingly recognized as an important factor. Studies demonstrated that the Y chromosome is not a 'genetic wasteland' and can be a useful genetic marker for interpreting various male-specific physiological and pathophysiological characteristics. Y chromosome harbors male‑specific genes, which either solely or in cooperation with their X-counterpart, and independent or in conjunction with sex hormones have a considerable impact on basic physiology and disease mechanisms in most or all tissues development. Furthermore, loss of Y chromosome and/or aberrant expression of Y chromosome genes cause sex differences in disease mechanisms. With the launch of the human proteome project (HPP), the association of Y chromosome proteins with pathological conditions has been increasingly explored. In this review, the involvement of Y chromosome genes in male-specific diseases such as prostate cancer and the cases that are more prevalent in men, such as cardiovascular disease, neurological disease, and cancers, has been highlighted. Understanding the molecular mechanisms underlying Y chromosome-related diseases can have a significant impact on the prevention, diagnosis, and treatment of diseases.

Epigenetic modification-dependent androgen receptor occupancy facilitates the ectopic TSPY1 expression in prostate cancer cells

Testis‐specific protein Y‐encoded 1 (TSPY1), a Y chromosome‐linked oncogene, is frequently activated in prostate cancers (PCa) and its expression is correlated with the poor prognosis of PCa. However, the cause of the ectopic transcription of TSPY1 in PCa remains unclear. Here, we observed that the methylation status in the CpG islands (CGI) of the TSPY1 promoter was negatively correlated with its expression level in different human samples. The acetyl‐histone H4 and trimethylated histone H3‐lysine 4, two post–translational modifications of histones occupying the TSPY1 promoter, facilitated the TSPY1 expression in PCa cells. In addition, we found that androgen accelerated the TSPY1 transcription on the condition of hypomethylated of TSPY1‐CGI and promoted PCa cell proliferation. Moreover, the binding of androgen receptor (AR) to the TSPY1 promoter, enhancing TSPY1 transcription, was detected in PCa cells. Taken together, our findings identified the regulation of DNA methylation, acting as a primary mechanism, on TSPY1 expression in PCa, and revealed that TSPY1 is an androgen‐AR axis‐regulated oncogene, suggesting a novel and potential target for PCa therapy.

Insights into the molecular features of the von Hippel-Lindau-like protein

We present an in silico characterization of the von Hippel-Lindau-like protein (VLP), the only known human paralog of the von Hippel-Lindau tumor suppressor protein (pVHL). Phylogenetic investigation showed VLP to be mostly conserved in upper mammals and specifically expressed in brain and testis. Structural analysis and molecular dynamics simulations show VLP to be very similar to pVHL three-dimensional organization and binding dynamics. In particular, conservation of elements at the protein interfaces suggests VLP to be a functional pVHL homolog potentially possessing multiple functions beyond HIF-1α-dependent binding activity. Our findings show that VLP may share at least seven interactors with pVHL, suggesting novel functional roles for this understudied human protein. These may occur at precise hypoxia levels where functional overlap with pVHL may permit a finer modulation of pVHL functions.

Comparison of Y-chromosome-linked TSPY, TSPY2, and PRAMEY genes in Taurus cattle, yaks, and interspecific hybrid bulls

Domestic yaks (Bos grunniens) and domestic Taurus cattle (Bos taurus) are closely related. An interesting phenomenon in interspecific crossings is male sterility in the F₁ hybrid (yattle) and F₂ backcross, with no late meiotic cells or spermatids in the seminiferous tubules. The mammalian Y chromosome is crucial for spermatogenesis and male fertility. This study investigated the copy number variations and mRNA of Y-transitional region genes TSPY2 (testis specific protein, Y-linked 2 and testis-specific Y-encoded protein 3-like) and PRAMEY (preferentially expressed antigen in melanoma, Y-linked), and Y-ampliconic region genes TSPY (testis-specific Y-encoded protein 1-like), ZNF280BY (zinc finger protein 280B, Y-linked) and HSFY (heat-shock transcription factor, Y-linked) in mature testes from Taurus cattle, yaks, and yattle. Phylogenetic trees divided 33 copies of TSPY into major 2 types (TSPY-T1 and TSPY-T2), 19 copies of TSPY2 into 2 types (TSPY2-T1 and T2), and 8 copies of PRAMEY into 4 types (PRAMEY-T1 to T4). Searching by the Basic Local Alignment Search Tool of the TSPY2 coding sequences in GenBank revealed that TSPY2 was conserved in Bovidae. The TSPY2-T2 sequences were absent, whereas PRAMEY-T2 and PRAMEY-T4 were amplified on the yak Y chromosome. The average copy numbers of TSPY-T2 and ZNF280BY were significantly different between cattle and yaks. The TSPY-T2, TSPY2, PRAMEY, ZNF280BY, and HSFY genes were uniquely or predominantly expressed in testes. Reverse-transcription quantitative PCR showed that the TSPY-T2, PRAMEY-T2, HSFY, ZNF280BY, protamine 1 (PRM1), and protamine 2 (PRM2) genes were almost not expressed in yattle. The PRM1 and PRM2 genes are used as positive markers for spermatozoa. Thus, our results showed that the genomic structure of the Y-transitional and Y-ampliconic region differed between Taurus cattle and yaks. Dysregulated expression of Y-ampliconic region genes TSPY-T2, HSPY, ZNF280BY, and Y-transitional region gene PRAMEY-T2 may be associated with hybrid male sterility in yattle.

Battle of the sexes: contrasting roles of testis-specific protein Y-encoded (TSPY) and TSPX in human oncogenesis

The Y-located testis-specific protein Y-encoded (TSPY) and its X-homologue TSPX originated from the same ancestral gene, but act as a proto-oncogene and a tumor suppressor gene, respectively. TSPY has specialized in male-specific functions, while TSPX has assumed the functions of the ancestral gene. Both TSPY and TSPX harbor a conserved SET/NAP domain, but are divergent at flanking structures. Specifically, TSPX contains a C-terminal acidic domain, absent in TSPY. They possess contrasting properties, in which TSPY and TSPX, respectively, accelerate and arrest cell proliferation, stimulate and inhibit cyclin B-CDK1 phosphorylation activities, have no effect and promote proteosomal degradation of the viral HBx oncoprotein, and exacerbate and repress androgen receptor (AR) and constitutively active AR variant, such as AR-V7, gene transactivation. The inhibitory domain has been mapped to the carboxyl acidic domain in TSPX, truncation of which results in an abbreviated TSPX exerting positive actions as TSPY. Transposition of the acidic domain to the C-terminus of TSPY results in an inhibitory protein as intact TSPX. Hence, genomic mutations/aberrant splicing events could generate TSPX proteins with truncated acidic domain and oncogenic properties as those for TSPY. Further, TSPY is upregulated by AR and AR-V7 in ligand-dependent and ligand-independent manners, respectively, suggesting the existence of a positive feedback loop between a Y-located proto-oncogene and male sex hormone/receptors, thereby amplifying the respective male oncogenic actions in human cancers and diseases. TSPX counteracts such positive feedback loop. Hence, TSPY and TSPX are homologues on the sex chromosomes that function at the two extremes of the human oncogenic spectrum.

Testis-specific protein, Y-linked 1 activates PI3K/AKT and RAS signaling pathways through suppressing IGFBP3 expression during tumor progression

The testis‐specific protein, Y‐linked 1 (TSPY1), a newly recognized cancer/testis antigen, has been suggested to accelerate tumor progression. However, the mechanisms underlying TSPY1 cancer‐related function remain limited. By mining the RNA sequencing data of lung and liver tumors from The Cancer Genome Atlas, we found frequent ectopic expression of TSPY1 in lung adenocarcinoma (LUAD) and liver hepatocellular carcinoma (LIHC), and the male‐specific protein was associated with higher mortality rate and worse overall survival in patients with LUAD and LIHC. Overexpression of TSPY1 promotes cell proliferation, invasiveness, and cycle transition and inhibits apoptosis, whereas TSPY1 knockdown has the opposite effects on these cancer cell phenotypes. Transcriptomic analysis revealed the involvement of TSPY1 in PI3K/AKT and RAS signaling pathways in both LUAD and LIHC cells, which was further confirmed by the increase in the levels of phosphorylated proteins in the PI3K‐AKT and RAS signaling pathways in TSPY1‐overexpressing cancer cells, and by the suppression on the activity of these two pathways in TSPY1‐knockdown cells. Further investigation identified that TSPY1 could directly bind to the promoter of insulin growth factor binding protein 3 (IGFBP3) to inhibit IGFBP3 expression and that downregulation of IGFBP3 increased the activity of PI3K/AKT/mTOR/BCL2 and RAS/RAF/MEK/ERK/JUN signaling in LUAD and LIHC cells. Taken together, the observations reveal a novel mechanism by which TSPY1 could contribute to the progression of LUAD and LIHC. Our finding is of importance for evaluating the potential of TSPY1 in immunotherapy of male tumor patients with TSPY1 expression.

The Y-linked proto-oncogene TSPY contributes to poor prognosis of the male hepatocellular carcinoma patients by promoting the pro-oncogenic and suppressing the anti-oncogenic gene expression

Background

Liver cancer is one of the major causes of cancer death worldwide, with significantly higher incidence and mortality among the male patients. Although sex hormones and their receptors could contribute to such sex differences, the story is incomplete. Genes on the male-specific region of the Y chromosome could play a role(s) in this cancer. TSPY is the putative gene for the gonadoblastoma locus on the Y chromosome (GBY) that is ectopically expressed in a subset of male hepatocellular carcinomas (HCCs). Although various studies showed that TSPY expression is associated with poor prognosis in the patients and its overexpression promotes cell proliferation of various cancer cell lines, it remains unclear how TSPY contributes to the clinical outcomes of the HCC patients. Identifying the downstream genes and pathways of TSPY actions would provide novel insights on its contribution(s) to male predominance in this deadly cancer.

Results

To determine the effects of TSPY on HCC, a TSPY transgene was introduced to the HCC cell line, HuH-7, and studied with RNA-Seq transcriptome analysis. The results showed that TSPY upregulates various genes associated with cell-cycle and cell-viability, and suppresses cell-death related genes. To correlate the experimental observations with those of clinical specimens, transcriptomes of male HCCs with high TSPY expression were analyzed with reference to those with silent TSPY expression from the Cancer Genome Atlas (TCGA). The comparative analysis identified 49 genes, which showed parallel expression patterns between HuH-7 cells overexpressing TSPY and clinical specimens with high TSPY expression. Among these 49 genes, 16 likely downstream genes could be associated with survival rates in HCC patients. The major upregulated targets were cell-cycle related genes and growth factor receptor genes, including CDC25B and HMMR, whose expression levels are negatively correlated with the patient survival rates. In contrast, PPARGC1A, SLC25A25 and SOCS2 were downregulated with TSPY expression, and possess favorable prognoses for HCC patients.

Conclusion

We demonstrate that TSPY could exacerbate the oncogenesis of HCC by differentially upregulate the expression of pro-oncogenic genes and downregulate those of anti-oncogenic genes in male HCC patients, thereby contributing to the male predominance in this deadly cancer.

Electronic supplementary material

The online version of this article (10.1186/s13578-019-0287-x) contains supplementary material, which is available to authorized users.

The X-linked tumor suppressor TSPX downregulates cancer-drivers/oncogenes in prostate cancer in a C-terminal acidic domain dependent manner

TSPX is a tumor suppressor gene located at Xp11.22, a prostate cancer susceptibility locus. It is ubiquitously expressed in most tissues but frequently downregulated in various cancers, including lung, brain, liver and prostate cancers. The C-terminal acidic domain (CAD) of TSPX is crucial for the tumor suppressor functions, such as inhibition of cyclin B/CDK1 phosphorylation and androgen receptor transactivation. Currently, the exact role of the TSPX CAD in transcriptional regulation of downstream genes is still uncertain. Using different variants of TSPX, we showed that overexpression of either TSPX, that harbors a CAD, or a CAD-truncated variant (TSPX[∆C]) drastically retarded cell proliferation in a prostate cancer cell line LNCaP, but cell death was induced only by overexpression of TSPX. Transcriptome analyses showed that TSPX or TSPX[∆C] overexpression downregulated multiple cancer-drivers/oncogenes, including MYC and MYB, in a CAD-dependent manner and upregulated various tumor suppressors in a CAD-independent manner. Datamining of transcriptomes of prostate cancer specimens in the Cancer Genome Atlas (TCGA) dataset confirmed the negative correlation between the expression level of TSPX and those of MYC and MYB in clinical prostate cancer, thereby supporting the hypothesis that the CAD of TSPX plays an important role in suppression of cancer-drivers/oncogenes in prostatic oncogenesis.

TSPY1 suppresses USP7-mediated p53 function and promotes spermatogonial proliferation

Testis-specific protein Y-linked 1 (TSPY1) is expressed predominantly in adult human spermatogonia and functions in the process of spermatogenesis; however, our understanding of the underlying mechanism is limited. Here we observed that TSPY1, as an interacting partner of TSPY-like 5 (TSPYL5), enhanced the competitive binding of TSPYL5 to ubiquitin-specific peptidase 7 (USP7) in conjunction with p53. This activity, together with its promotion of TSPYL5 expression by acting as a transcription factor, resulted in increased p53 ubiquitylation. Moreover, TSPY1 could decrease the p53 level by inducing the degradation of ubiquitinated USP7. We demonstrated that the promotion of p53 degradation by TSPY1 influenced the activity of p53 target molecules (CDK1, p21, and BAX) to expedite the G2/M phase transition and decrease cell apoptosis, accelerating cell proliferation. Taken together, the observations reveal the significance of TSPY1 as a suppressor of USP7-mediated p53 function in inhibiting p53-dependent cell proliferation arrest. By simulating TSPY1 function in Tspy1-deficient spermatogonia derived from mouse testes, we found that TSPY1 could promote spermatogonial proliferation by decreasing the Usp7-modulated p53 level. The findings suggest an additional mechanism underlying the regulation of spermatogonial p53 function, indicating the significance of TSPY1 in germline homeostasis maintenance and the potential of TSPY1 in regulating human spermatogonial proliferation via the USP7-mediated p53 signaling pathway.

Prostate cancer susceptibility and growth linked to Y chromosome genes

The role of Y chromosome in prostate cancer progression and incidence is not well known. Among the 46 chromosomes, Y chromosome determines the male gender. The Y chromosome is smaller than the X chromosome and contains only 458 genes compared to over 2000 genes found in the X chromosome. The Y chromosome is prone to high mutation rates, created exclusively in sperm cells due to the highly oxidative environment of the testis. Y chromosome harbors epigenetic information, which affects the expression of genes associated with the incidence and progression of prostate cancer. In this review, we focus on Y chromosome related genetic abnormalities, likely to be involved in the development and progression of prostate cancer.

Highly dynamic temporal changes of TSPY gene copy number in aging bulls

The Y-chromosomal TSPY gene is one of the highest copy number mammalian protein coding gene and represents a unique biological model to study various aspects of genomic copy number variations. This study investigated the age-related copy number variability of the bovine TSPY gene, a new and unstudied aspect of the biology of TSPY that has been shown to vary among cattle breeds, individual bulls and somatic tissues. The subjects of this prospective 30-month long study were 25 Holstein bulls, sampled every six months. Real-time quantitative PCR was used to determine the relative TSPY copy number (rTSPY CN) and telomere length in the DNA samples extracted from blood. Twenty bulls showed an altered rTSPY CN after 30 months, although only 9 bulls showed a significant change (4 significant increase while 5 significant decrease, P<0.01). The sequential sampling provided the flow of rTSPY CN over six observations in 30 months and wide-spread variation of rTSPY CN was detected. Although a clear trend of the direction of change was not identifiable, the highly dynamic changes of individual rTSPY CN in aging bulls were observed here for the first time. In summary we have observed a highly variable rTSPY CN in bulls over a short period of time. Our results suggest the importance of further long term studies of the dynamics of rTSPY CN variablility.

De novo sequencing and comparative analysis of testicular transcriptome from different reproductive phases in freshwater spotted snakehead Channa punctatus

The spotted snakehead Channa punctatus is a seasonally breeding teleost widely distributed in the Indian subcontinent and economically important due to high nutritional value. The declining population of C. punctatus prompted us to focus on genetic regulation of its reproduction. The present study carried out de novo testicular transcriptome sequencing during the four reproductive phases and correlated differential expression of transcripts with various testicular events in C. punctatus. The Illumina paired-end sequencing of testicular transcriptome from resting, preparatory, spawning and postspawning phases generated 41.94, 47.51, 61.81 and 44.45 million reads, and 105526, 105169, 122964 and 106544 transcripts, respectively. Transcripts annotated using Rattus norvegicus reference protein sequences and classified under various subcategories of biological process, molecular function and cellular component showed that the majority of the subcategories had highest number of transcripts during spawning phase. In addition, analysis of transcripts exhibiting differential expression during the four phases revealed an appreciable increase in upregulated transcripts of biological processes such as cell proliferation and differentiation, cytoskeleton organization, response to vitamin A, transcription and translation, regulation of angiogenesis and response to hypoxia during spermatogenically active phases. The study also identified significant differential expression of transcripts relevant to spermatogenesis (mgat3, nqo1, hes2, rgs4, cxcl2, alcam, agmat), steroidogenesis (star, tkt, gipc3), cell proliferation (eef1a2, btg3, pif1, myo16, grik3, trim39, plbd1), cytoskeletal organization (espn, wipf3, cd276), sperm development (klhl10, mast1, hspa1a, slc6a1, ros1, foxj1, hipk1), and sperm transport and motility (hint1, muc13). Analysis of functional annotation and differential expression of testicular transcripts depending on reproductive phases of C. punctatus helped in developing a comprehensive understanding on genetic regulation of spermatogenic and steroidogenic events in seasonally breeding teleosts. Our findings provide the basis for future investigation on the precise role of testicular genes in regulation of seasonal reproduction in male teleosts.

The Y-located proto-oncogene TSPY exacerbates and its X-homologue TSPX inhibits transactivation functions of androgen receptor and its constitutively active variants

The gonadoblastoma gene, testis-specific protein Y-encoded (TSPY), on the Y chromosome and its X-homologue, TSPX, are cell cycle regulators and function as a proto-oncogene and a tumor suppressor respectively in human oncogenesis. TSPY and TSPX competitively bind to the androgen receptor (AR) and AR variants, such as AR-V7, at their conserved SET/NAP domain, and exacerbate and repress the transactivation of the AR/AR-V7 target genes in ligand dependent and independent manners respectively. The inhibitory domain has been mapped to the carboxyl acidic domain of TSPX, truncation of which renders TSPX to be stimulatory while its transposition to the C-terminus of TSPY results in an inhibitory hybrid protein. TSPY and TSPX co-localize with the endogenous AR, in the presence of ligand, on the promoters and differentially regulate the expression of the endogenous AR target genes in the androgen-responsive LNCaP prostate cancer cells. Transcriptome analysis shows that TSPY and TSPX expressions differentially affect significant numbers of canonical pathways, upstream regulators and cellular functions. Significantly, among the common ones, TSPY activates and TSPX inhibits numerous growth-related and oncogenic canonical pathways and cellular functions in the respective cell populations. Hence, TSPY and TSPX exert opposing effects on the transactivation functions of AR and AR-Vs important for various physiological and disease processes sensitive to male sex hormone actions, thereby not only affecting the pathogenesis of male-specific prostate cancer but also likely contributing to sex differences in the health and diseases of man.

Identification of a TSPY co-expression network associated with DNA hypomethylation and tumor gene expression in somatic cancers

Testis specific protein Y-encoded (TSPY) is a Y-located proto-oncogene predominantly expressed in normal male germ cells and various types of germ cell tumor. Significantly, TSPY is frequently expressed in somatic cancers including liver cancer but not in adjacent normal tissues, suggesting that ectopic TSPY expression could be associated with oncogenesis in non-germ cell cancers. Various studies demonstrated that TSPY expression promotes growth and proliferation in cancer cells; however, its relationship to other oncogenic events in TSPY-positive cancers remains unknown. The present study seeks to correlate TSPY expression with other molecular features in clinical cancer samples, by analyses of RNA-seq transcriptome and DNA methylation data in the Cancer Genome Atlas (TCGA) database. A total of 53 genes, including oncogenic lineage protein 28 homolog B (LIN28B) gene and RNA-binding motif protein Y-linked (RBMY) gene, are identified to be consistently co-expressed with TSPY, and have been collectively designated as the TSPY co-expression network (TCN). TCN genes were simultaneously activated in subsets of liver hepatocellular carcinoma (30%) and lung adenocarcinoma (10%) regardless of pathological stage, but only minimally in other cancer types. Further analysis revealed that the DNA methylation level was globally lower in the TCN-active than TCN-silent cancers. The specific expression and methylation patterns of TCN genes suggest that they could be useful as biomarkers for the diagnosis, prognosis and clinical management of cancers, especially those for liver and lung cancers, associated with TSPY co-expression network genes.

Roles of the Y chromosome genes in human cancers

Male and female differ genetically by their respective sex chromosome composition, that is, XY as male and XX as female. Although both X and Y chromosomes evolved from the same ancestor pair of autosomes, the Y chromosome harbors male-specific genes, which play pivotal roles in male sex determination, germ cell differentiation, and masculinization of various tissues. Deletions or translocation of the sex-determining gene, SRY, from the Y chromosome causes disorders of sex development (previously termed as an intersex condition) with dysgenic gonads. Failure of gonadal development results not only in infertility, but also in increased risks of germ cell tumor (GCT), such as gonadoblastoma and various types of testicular GCT. Recent studies demonstrate that either loss of Y chromosome or ectopic expression of Y chromosome genes is closely associated with various male-biased diseases, including selected somatic cancers. These observations suggest that the Y-linked genes are involved in male health and diseases in more frequently than expected. Although only a small number of protein-coding genes are present in the male-specific region of Y chromosome, the impacts of Y chromosome genes on human diseases are still largely unknown, due to lack of in vivo models and differences between the Y chromosomes of human and rodents. In this review, we highlight the involvement of selected Y chromosome genes in cancer development in men.

The potential contributions of a Y-located protooncogene and its X homologue in sexual dimorphisms in hepatocellular carcinoma

There is a significant sex disparity favoring males among hepatocellular carcinoma (HCC) patients. Although various risk factors have been identified, the exact etiology of such sexual dimorphism(s) in HCC is uncertain. Previous studies showed that overexpression of the Y-located protooncogene, testis-specific protein Y encoded (TSPY), promotes cell proliferation and oncogenesis whereas its X-located homologue, TSPYhomologue X (TSPX), retards cell cycle and oncogenic progression. Furthermore, TSPX promotes proteasomal degradation of hepatitis B virus-encoded X oncoprotein and hence could serve as a tumor suppressor in virus-associated HCC. Using immunohistochemistry and reverse-transcription polymerase chain reaction analysis, we had examined the expression of TSPY and TSPX with reference to other established biomarkers in HCC and related liver cancers. Our results demonstrated that 55 (19.2%) of 287 male cases were TSPY positive in immunohistochemistry of tissue arrays, and 15 (46.9%) of 32 male cases were TSPY positive in reverse-transcription polymerase chain reaction analysis of clinical samples. TSPY expression was closely associated with the expression of HCC biomarkers, such as glypican 3. In contrast, TSPX expression was down-regulated in 54.5% of total tumor/nontumorous paired samples (18/33) and negatively associated with those of TSPY, glypican 3, and forkhead box M1 (FOXM1) and was positively associated with that of a tumor suppressor, insulin-like growth factor binding protein 3. The present findings support the hypothesis that the oncogenic events leading to an ectopic activation of the Y-located protooncogene TSPY and/or inactivating mutation/epigenetic silencing of the X-located tumor suppressor gene TSPX could collectively contribute to the sexual dimorphism(s) in HCC and related liver cancers in male-biased manners.

The Y-located gonadoblastoma gene TSPY amplifies its own expression through a positive feedback loop in prostate cancer cells

The testis-specific protein Y-encoded (TSPY) is a repetitive gene located on the gonadoblastoma region of the Y chromosome, and has been considered to be the putative gene for this oncogenic locus on the male-only chromosome. It is expressed in spermatogonial cells and spermatocytes in normal human testis, but abundantly in gonadoblastoma, testicular germ cell tumors and a variety of somatic cancers, including melanoma, hepatocellular carcinoma and prostate cancer. Various studies suggest that TSPY accelerates cell proliferation and growth, and promotes tumorigenesis. In this report, we show that TSPY could bind directly to the chromatin/DNA at exon 1 of its own gene, and greatly enhance the transcriptional activities of the endogenous gene in the LNCaP prostate cancer cells. Domain mapping analyses of TSPY have localized the critical and sufficient domain to the SET/NAP-domain. These results suggest that TSPY could efficiently amplify its expression and oncogenic functions through a positive feedback loop, and contribute to the overall tumorigenic processes when it is expressed in various human cancers.

Over-expressed Testis-specific Protein Y-encoded 1 as a novel biomarker for male hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a male-predominant cancer. Previous studies have focused on the sex-related disparity in HCC, but the underlying mechanism remains unclear. Here, we aimed to discover characteristic biomarkers for male HCC. Clinical samples were subjected to iTRAQ labeling followed by 2DLC-ESI-MS/MS analysis. Seventy-three differential proteins containing 16 up-regulated and 57 down-regulated proteins were screened out in the male HCC group compared to that in female HCC group. Testis-specific Protein Y-encoded 1(TSPY1) is characteristically present in male HCC and was chosen for further investigation. The data from the functional effects of TSPY1 indicated that over-expression of TSPY1 could potentiate HCC cell proliferation, increase soft agar colonization, induce higher cell invasive ability and correlate with the metastatic potential of the HCC cell lines. In addition, TSPY1 and androgen receptor (AR) were co-expressed simultaneously in HCC cell lines as well as in HCC tissue. TSPY1 up- or down-regulation could lead to a high or low level expression of AR. These results implied that TSPY1 may be included in the regulation of AR expression involved in male HCC and it may act as a novel biomarker for male HCC.

Expression of a Y-located human proto-oncogene TSPY in a transgenic mouse model of prostate cancer

BACKGROUND

The human TSPY is the putative gene for the gonadoblastoma locus on the Y chromosome (GBY). Various molecular, pathological and transgenic mouse studies suggest that TSPY is a Y-located proto-oncogene contributing to the initiation/progression in human cancers, including germ cell tumors and various somatic cancers, such as prostate and liver cancer, and melanoma. The TgTSPY9 transgenic mouse line harbors a 8.2-kb human TSPY structural gene, which is tandemly integrated in the mouse Y chromosome, and expressed in a similar pattern as that of the endogenous gene in the human genome. This mouse model of human TSPY gene offers an opportunity to examine its behavior and potential contribution in various mouse models of human diseases, such as human cancers. We had investigated the expression of such TSPY-transgene in the LADY mouse model of prostate cancer, harboring a SV40 T antigen gene directed by a rat probasin promoter; and compared the expression pattern with those of endogenous TSPY gene and biomarkers in human prostate cancer specimens.

RESULTS

By introducing the Y-located TSPY-transgene to the LADY mice, we had examined the expression pattern of the human TSPY during prostatic oncogenesis in this mouse model of prostate cancer. Our results showed that the TSPY-transgene was activated in selected areas of the hypercellular stroma but not in the intraepithelial cells/neoplasia in the prostates of TgTSPY9/LADY mice. Using a specific biomarker, FOXA1, for epithelial cells, we demonstrated that TSPY-positive cells proliferated exclusively in the cancerous stroma in the LADY model at late stages of tumorigenesis. In contrast, in the human situation, TSPY was predominantly co-expressed with FOXA1 in the epithelial cells of PIN lesions and FOXA1 and another cancer biomarker, AMACR, in the adenocarcinoma cells in clinical prostate cancer samples of various degrees of malignancy.

CONCLUSIONS

Our data show that human TSPY could be abnormally activated during prostatic oncogenesis, and could possibly contribute to the heterogeneity of prostate cancer. The differential expression patterns of the human TSPY between the LADY mouse model and clinical prostate cancer suggest potential limitations of current mouse models for studies of either TSPY behavior in diseased conditions or prostate cancer development.

The more basic isoform of eEF1A relates to tumour cell phenotype and is modulated by hyper-proliferative/differentiating stimuli in normal lymphocytes and CCRF-CEM T-lymphoblasts

The elongation factor 1A proteins (eEF1A1/A2) are known to play a role in tumours. We previously found that a more basic isoform of eEF1A (MBI-eEF1A) is present in the cytoskeletal/nuclear-enriched extracts of CCRF-CEM T-lymphoblasts but not in those of normal lymphocytes. To obtain deeper knowledge about MBI-eEF1A biology, we investigate from which of the eEF1A proteins, eEF1A1 or eEF1A2, MBI-eEF1A originates and the possibility that its appearance can be modulated by the differentiated or proliferative cell status. CCRF-CEM T-lymphoblasts and normal lymphocytes were cultured with or without differentiation/pro-proliferative stimuli (Phorbol 12-Myristate 13-Acetate (PMA) alone or the combination of phytohaemagglutinin (PHA) with PMA, respectively), and the presence of MBI-eEF1A evaluated together with that of the eEF1A1/A2 mRNAs. Our data indicate that the MBI-eEF1A may derive from eEF1A1 as eEF1A2 is not expressed in CCRF-CEM and normal lymphocytes. Moreover, MBI-eEF1A is inducible in normal lymphocytes upon hyper-proliferative stimuli application; in CCRF-CEM, its presence can be abrogated by PMA-induced differentiation. Finally, MBI-eEF1A may have a functional role in hyper-proliferating/tumour cells as its disappearance reduces the growth of CCRF-CEM and that of PHA/PMA-stimulated lymphocytes. The presented data suggest that MBI-eEF1A may be related to oncogenic cell phenotype, rising the possibility to use MBI-eEF1A as target for novel therapeutic strategies.

A fresh look at the male-specific region of the human Y chromosome

The Chromosome-centric Human Proteome Project (C-HPP) aims to systematically map the entire human proteome with the intent to enhance our understanding of human biology at the cellular level. This project attempts simultaneously to establish a sound basis for the development of diagnostic, prognostic, therapeutic, and preventive medical applications. In Iran, current efforts focus on mapping the proteome of the human Y chromosome. The male-specific region of the Y chromosome (MSY) is unique in many aspects and comprises 95% of the chromosome's length. The MSY continually retains its haploid state and is full of repeated sequences. It is responsible for important biological roles such as sex determination and male fertility. Here, we present the most recent update of MSY protein-encoding genes and their association with various traits and diseases including sex determination and reversal, spermatogenesis and male infertility, cancers such as prostate cancers, sex-specific effects on the brain and behavior, and graft-versus-host disease. We also present information available from RNA sequencing, protein-protein interaction, post-translational modification of MSY protein-coding genes and their implications in biological systems. An overview of Human Y chromosome Proteome Project is presented and a systematic approach is suggested to ensure that at least one of each predicted protein-coding gene's major representative proteins will be characterized in the context of its major anatomical sites of expression, its abundance, and its functional relevance in a biological and/or medical context. There are many technical and biological issues that will need to be overcome in order to accomplish the full scale mapping.

Sequence recombination in exon 1 of the TSPY gene in men with impaired fertility

AIM

The aim of this study was to evaluate TSPY (testis specific protein on the Y chromosome) gene and 5'UTR (UnTranslated Region) polymorphisms in men with impaired fertility compared to fertile controls.

METHODS

We analyzed 72 infertile men and 31 fertile controls usingconventional sequencing analysis to find crucial SNPs (single nucleotide polymorphism) and other changes.

RESULTS

The most remarkable changes were found in the 1(st) exon only. In one half of the both infertile men and fertile controls, the most frequent finding was 26 SNPs with a similar pattern. In the other half we found highly relevant changes, generating a stop codon in the first third of exon 1. Early termination cut down the protein by 78.5%. This kind of change was not found in the fertile controls. No correlation was found between the spermiogram and the changes leading to the stop codon. The distribution of men with deletions, insertion and higher gene copy number was not statistically different.

CONCLUSION

The changes found in exon 1 in infertile men could fundamentally affect the process of spermatogenesis. These findings could significantly enhance our understanding of the molecular-genetic causes of male infertility.

The X-linked tumor suppressor TSPX interacts and promotes degradation of the hepatitis B viral protein HBx via the proteasome pathway

Hepatitis B virus (HBV) infection is a major risk for hepatocellular carcinoma (HCC), and it is a serious global health problem with two billion people exposed to it worldwide. HBx, an essential factor for viral replication and a putative oncoprotein encoded by the HBV genome, has been shown to promote oncogenic properties at multiple sites in HBV-infected liver cells. The expression level of HBx closely associates with the development and progression of HCC, therefore the mechanism(s) regulating the stability of HBx is important in oncogenesis of HBV-infected cells. We demonstrate that the X-linked tumor suppressor TSPX enhances the degradation of HBx through the ubiquitin-proteasome pathway. TSPX interacts with both HBx and a proteasome 19S lid subunit RPN3 via its C-terminal acidic tail. Most importantly, over-expression of RPN3 protects HBx from, and hence acts as a negative regulator for, proteasome-dependent degradation. TSPX abrogates the RPN3-depedent stabilization of HBx, suggesting that TSPX and RPN3 act competitively in regulation of HBx stability. Since mutation and/or epigenetic repression of X-located tumor suppressor gene(s) could significantly predispose males to human cancers, our data suggest that TSPX-induced HBx degradation could play key role(s) in hepatocarcinogenesis among HBV-infected HCC patients.

Expression of the human TSPY gene in the brains of transgenic mice suggests a potential role of this Y chromosome gene in neural functions

The testis specific protein Y-encoded (TSPY) is a member of TSPY/SET/NAP1 superfamily, encoded within the gonadoblastoma locus on the Y chromosome. TSPY shares a highly conserved SET/NAP-domain responsible for protein--protein interaction among TSPY/SET/NAP1 proteins. Accumulating data, so far, support the role of TSPY as the gonadoblastoma gene, involved in germ cell tumorigenesis. The X-chromosome homolog of TSPY, TSPX is expressed in various tissues at both fetal and adult stages, including the brain, and is capable of interacting with the multi-domain adapter protein CASK, thereby influencing the synaptic and transcriptional functions and developmental regulation of CASK in the brain and other neural tissues. Similar to TSPX, we demonstrated that TSPY could interact with CASK at its SET/NAP-domain in cultured cells. Transgenic mice harboring a human TSPY gene and flanking sequences showed specific expression of the human TSPY transgene in both testis and brain. The neural expression pattern of the human TSPY gene overlapped with those of the endogenous mouse Cask and Tspx gene. Similarly with TSPX, TSPY was co-localized with CASK in neuronal axon fibers in the brain, suggesting a potential role(s) of TSPY in development and/or physiology of the nervous system.

Role of the Y-located putative gonadoblastoma gene in human spermatogenesis

The gonadoblastoma locus on the human Y chromosome (GBY) is postulated to serve normal functions in spermatogenesis, but could exert oncogenic properties in predisposing susceptible germ cells to tumorigenesis in incompatible niches such as streaked gonads in XY sex reversed patients or dysfunctional testis in males. The testis-specific protein Y-linked (TSPY) repeat gene has recently been demonstrated to be the putative gene for GBY, based on its location on the GBY critical region, expression patterns in early and late stages of gonadoblastoma and ability to induce gonadoblastoma-like structures in the ovaries of transgenic female mice. Over-expression of TSPY accelerates G(2)/M progression in the cell cycle by enhancing the mitotic cyclin B-CDK1 kinase activities. Currently the normal functions of TSPY in spermatogenesis are uncertain. Expression studies of TSPY, and its X-homologue, TSPX, in normal human testis suggest that TSPY is co-expressed with cyclin B1 in spermatogonia and various stages of spermatocytes while TSPX is principally expressed in Sertoli cells in the human testis. The co-expression pattern of TSPY and cyclin B1 in spermatogonia and spermatocytes suggest respectively that 1) TSPY is important for male spermatogonial cell replication and renewal in the testis; and 2) TSPY could be a catalyst/meiotic factor essential for augmenting the activities of cyclin B-cyclin dependent kinases, important for the differentiation of the spermatocytes in prophase I and in preparation for consecutive rounds of meiotic divisions without an intermediate interphase during spermatogenesis.

TSPY and Male Fertility

Spermatogenesis requires the concerted action of thousands of genes, all contributing to its efficiency to a different extent. The Y chromosome contains several testis-specific genes and among them the AZF region genes on the Yq and the TSPY1 array on the Yp are the most relevant candidates for spermatogenic function. TSPY1 was originally described as the putative gene for the gonadoblastoma locus on the Y (GBY) chromosome. Besides its oncogenic properties, expression analyses in the testis and in vitro and in vivo studies all converge on a physiological involvement of the TSPY1 protein in spermatogenesis as a pro-proliferative factor. The majority of TSPY1 copies are arranged in 20.4 kb of tandemly repeated units, with different copy numbers among individuals. Our recent study addressing the role of TSPY1 copy number variation in spermatogenesis reported that TSPY1 copy number influences spermatogenic efficiency and is positively correlated with sperm count. This finding provides further evidence for a role of TSPY1 in testicular germ cell proliferation and stimulates future research aimed at evaluating the relationship between the copy number and the protein expression level of the TSPY1 gene.

Expression of the Y-Encoded TSPY is Associated with Progression of Prostate Cancer

TSPY is a Y-encoded gene that is expressed in normal testicular germ cells and various cancer types including germ cell tumor, melanoma, hepatocellular carcinoma, and prostate cancer. Currently, the correlation between TSPY expression and oncogenic development has not been established, particularly in somatic cancers. To establish such correlation, we analyzed the expression of TSPY, in reference to its interactive oncoprotein, EEF1A, tumor biomarker, AMACR, and normal basal cell biomarker, p63, in 41 cases of clinical prostate cancers (CPCa), 17 cases of latent prostate cancers (LPCa), and 19 cases of non-cancerous prostate (control) by immunohistochemistry. Our results show that TSPY was detected more frequently (78%) in the clinical prostate cancer specimens than those of latent prostate cancer (47%) and control (50%). In the latent cancer group, the levels of TSPY expression could be correlated with increasing Gleason grades. TSPY expression was detected in seven out of nine high-grade latent cancer samples (Gleason 7 and more). The expression of the TSPY binding partner EEF1A was detectable in all prostate specimens, but the levels were higher in cancer cells in clinical and latent prostate cancer specimens than normal prostatic cells. These observations suggest that expressions of TSPY and its binding partner EEF1A are associated with the development and progression of prostate cancer.

Transgenic Mouse Studies to Understand the Regulation, Expression and Function of the Testis-Specific Protein Y-Encoded (TSPY) Gene

The TSPY gene, which encodes the testis-specific protein, Y-encoded, was first discovered and characterized in humans, but orthologous genes were subsequently identified on the Y chromosome of many other placental mammals. TSPY is expressed in the testis and to a much lesser extent in the prostate gland, and it is assumed that TSPY serves function in spermatogonial proliferation and/or differentiation. It is further supposed that TSPY is involved in male infertility and exerts oncogenic effects in gonadal and prostate tumor formation. As a member of the TSPY/SET/NAP protein family, TSPY is able to bind cyclin B types, and stimulates the cyclin B1-CDK1 kinase activity, thereby accelerating the G₂/M phase transition of the cell cycle of target cells. Because the laboratory mouse carries only a nonfunctional Y-chromosomal Tspy-ps pseudogene, a knockout mouse model for functional research analyses is not a feasible approach. In the last decade, three classical transgenic mouse models have been developed to contribute to our understanding of TSPY regulation, expression and function. The different transgenic mouse approaches and their relevance for studying TSPY regulation, expression and function are discussed in this review.

Eef1a2 promotes cell growth, inhibits apoptosis and activates JAK/STAT and AKT signaling in mouse plasmacytomas

Background

The canonical function of EEF1A2, normally expressed only in muscle, brain, and heart, is in translational elongation, but recent studies suggest a non-canonical function as a proto-oncogene that is overexpressed in a variety of solid tumors including breast and ovary. Transcriptional profiling of a spectrum of primary mouse B cell lineage neoplasms showed that transcripts encoding EEF1A2 were uniquely overexpressed in plasmacytomas (PCT), tumors of mature plasma cells. Cases of human multiple myeloma expressed significantly higher levels of EEF1A2 transcripts than normal bone marrow plasma cells. High-level expression was also a feature of a subset of cell lines developed from mouse PCT and from the human MM.

Methodology/Principal Findings

Heightened expression of EEF1A2 was not associated with increased copy number or coding sequence mutations. shRNA-mediated knockdown of Eef1a2 transcripts and protein was associated with growth inhibition due to delayed G1-S progression, and effects on apoptosis that were seen only under serum-starved conditions. Transcriptional profiles and western blot analyses of knockdown cells revealed impaired JAK/STAT and PI3K/AKT signaling suggesting their contributions to EEF1A2-mediated effects on PCT induction or progression.

Conclusions/Significance

EEF1A2 may play contribute to the induction or progression of some PCT and a small percentage of MM. Eef1a2 could also prove to be a useful new marker for a subset of MM and, ultimately, a possible target for therapy.

Partial rescue of the KIT-deficient testicular phenotype in KitW-v/KitW-v Tg(TSPY) mice

TSPY encodes the testis-specific protein Y-linked. In man, expression of TSPY is restricted to the testis, where TSPY is expressed in spermatogonia, primary spermatocytes, and round spermatids, and to the prostate gland. There is circumstantial evidence that TSPY is involved in spermatogonial proliferation and gonadal tumorigenesis. Because the laboratory mouse carries the Tspy gene in a naturally silenced state (Tspy-ps), we previously restored TSPY activity in mice and generated a TSPY transgenic mouse line in which the organization and expression of the human TSPY transgene follow the human pattern. In the present study, we generated TSPY transgenic KIT-deficient Kit(W-v)/Kit(W-v) mice and analyzed the histology of the testes and epididymides in order to contribute to understanding TSPY function in early germ cell development and spermatogenesis. The KIT receptor and its ligand KITL, previously called stem cell factor, have an indispensable role in hematopoiesis, melanogenesis, and gametogenesis. Homozygous Kit(W-v) mutant male mice on a C57BL/6J background with a mutation in the Kit gene are infertile due to an almost total loss of germ cells in the testes. In this study, histological analyses of testes and epididymides showed an increased number of meiotic and postmeiotic germ cells in Kit(W-v)/Kit(W-v) Tg(TSPY) mice compared with age-matched Kit(W-v)/Kit(W-v) controls. TSPY was able to restore fertility of some but not all TSPY transgenic Kit(W-v)/Kit(W-v) males. Our findings show that TSPY is able to partially rescue spermatogenesis and fertility of Kit(W-v)/Kit(W-v) mutants and thereby point to a putative role of TSPY in fetal and adult germ cell proliferation.

Y chromosome TSPY copy numbers and semen quality

OBJECTIVE

To determine whether variation in testis-specific protein Y-encoded (TSPY) gene copy number affects semen quality.

DESIGN

Nested case-control study.

SETTING

University hospital.

PATIENT(S)

From a consecutive cohort of 1,016 male partners of subfertile couples, unselected for sperm counts, we selected as cases 100 men with the lowest total number of progressively motile sperm (TMC) and as controls, 100 men with the highest total number of progressively motile sperm.

INTERVENTION(S)

Quantitative real-time polymerase chain reaction (PCR) and Southern blot to determine TSPY copy number.

MAIN OUTCOME MEASURE(S)

TSPY copy number.

RESULT(S)

The quantitative PCR method showed excellent agreement with the Southern blot analysis. Cases had a median TSPY copy number of 35 (range 20-73), whereas controls had a median TSPY copy number of 34 (range 26-76). This difference was not statistically significant.

CONCLUSION(S)

We found no association between TSPY copy numbers and severe spermatogenic failure. The observed variation in TSPY copy number therefore appears to have no functional consequences for semen quality.

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.

Gonadoblastoma locus and the TSPY gene on the human Y chromosome

The gonadoblastoma (GBY) locus is the only oncogenic locus on the human Y chromosome. It is postulated to serve a normal function in the testis, but could exert oncogenic effects in dysgenetic gonads of individuals with intersex and/or dysfunctional testicular phenotypes. Recent studies establish the testis-specific protein Y-encoded (TSPY) gene to be the putative gene for GBY. TSPY serves normal functions in male stem germ cell proliferation and differentiation, but is ectopically expressed in early and late stages of gonadoblastomas, testicular carcinoma in situ (the premalignant precursor for all testicular germ cell tumors), seminomas, and selected nonseminomas. Aberrant TSPY expression stimulates protein synthetic activities, accelerates cell proliferation, and promotes tumorigenicity in athymic mice. TSPY binds to type B cyclins, enhances an activated cyclin B-CDK1 kinase activity, and propels a rapid G(2)/M transition in the cell cycle. TSPY also counteracts the normal functions of its X-homologue, TSPX, which also binds to cyclin B and modulates the cyclin B-CDK1 activity to insure a proper G(2)/M transition in the cell cycle. Hence, ectopic expression and actions of the Y-located TSPY gene in incompatible germ cells, such as those in dysgenetic or ovarian environments and dysfunctional testis, disrupt the normal cell cycle regulation and predispose the host cells to tumorigenesis. The contrasting properties of TSPY and TSPX suggest that somatic cancers, such as intracranial germ cell tumors, melanoma, and hepatocellular carcinoma, with detectable TSPY expression could exhibit sexual dimorphisms in the initiation and/or progression of the respective oncogenesis.