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

Evolution of Testicular Germ Cell Tumors in the Molecular Era With Histogenetic Implications

The current WHO classification of testicular germ cell tumors is based on the pathogenesis of the tumors driven by different genomic events. The germ cell neoplasia in situ is the precursor lesion for all malignant germ cell tumors. The current understanding of pathogenesis is that the developmental and environmental factors with the erasure of parental genomic imprinting lead to the development of abnormal gonocytes that settle in the "spermatogonial Niche" in seminiferous tubules. The abnormal primordial germ cells in the seminiferous tubules give rise to pre-GCNIS cells under the influence of TPSY and OCT4 genes. The whole genome duplication events give rise to germ cell neoplasia in situ, which further acquires alterations in 12p along with NRAS and KRAS mutations to produce seminoma. A subset of seminomas acquires KIT mutation and does not differentiate further. The remaining KIT-stable seminomas differentiate to nonseminomatous GCTs after obtaining recurrent chromosomal losses, epigenetic modification, and posttranscriptional regulation by multiple genes. Nonseminomatous germ cell tumors also develop directly from differentiated germ cell neoplasia in situ. TP53 pathway with downstream drivers may give rise to somatic-type malignancies of GCT. The GCTs are remarkably sensitive to cisplatin-based combination chemotherapy; however, resistance to cisplatin develops in up to 8% of tumors and appears to be driven by TP53/MDM2 gene mutations. Serum and Plasma miRNAs show promise in diagnosing, managing, and following up on these tumors. The mechanisms underlying the development of most tumors have been elucidated; however, additional studies are required to pinpoint the events directing specific characteristics. Advances in identifying specific molecular markers have been seen recently and may be adopted as gold standards in the future.

Further Association of Germline CHEK2 Loss-of-Function Variants with Testicular Germ Cell Tumors

Testicular germ cell tumors (TGCTs) represent the most frequent malignancy in young adult men and have one the highest heritability rates among all cancers. A recent multicenter case-control study identified CHEK2 as the first moderate-penetrance TGCT predisposition gene. Here, we analyzed CHEK2 in 129 TGCT cases unselected for age of onset, histology, clinical outcome, and family history of any cancer, and the frequency of identified variants was compared to findings in 27,173 ancestry-matched cancer-free men. We identified four TGCT cases harboring a P/LP variant in CHEK2 (4/129, 3.10%), which reached statistical significance (p = 0.0191; odds ratio (OR), 4.06; 95% CI, 1.59-10.54) as compared to the control group. Cases with P/LP variants in CHEK2 developed TGCT almost 6 years earlier than individuals with CHEK2 wild-type alleles (5.67 years; 29.5 vs. 35.17). No association was found between CHEK2 status and further clinical and histopathological characteristics, including histological subtypes, the occurrence of aggressive TGCT, family history of TGCT, and family history of any cancer. In addition, we found significant enrichment for the low-penetrance CHEK2 variant p.Ile157Thr (p = 0.0259; odds ratio (OR), 3.69; 95% CI, 1.45-9.55). Thus, we provide further independent evidence of CHEK2 being a moderate-penetrance TGCT predisposition gene.

Breaking the Mold: Epigenetics and Genomics Approaches Addressing Novel Treatments and Chemoresponse in TGCT Patients

Testicular germ-cell tumors (TGCT) have been widely recognized for their outstanding survival rates, commonly attributed to their high sensitivity to cisplatin-based therapies. Despite this, a subset of patients develops cisplatin resistance, for whom additional therapeutic options are unsuccessful, and ~20% of them will die from disease progression at an early age. Several efforts have been made trying to find the molecular bases of cisplatin resistance. However, this phenomenon is still not fully understood, which has limited the development of efficient biomarkers and precision medicine approaches as an alternative that could improve the clinical outcomes of these patients. With the aim of providing an integrative landscape, we review the most recent genomic and epigenomic features attributed to chemoresponse in TGCT patients, highlighting how we can seek to combat cisplatin resistance through the same mechanisms by which TGCTs are particularly hypersensitive to therapy. In this regard, we explore ongoing treatment directions for resistant TGCT and novel targets to guide future clinical trials. Through our exploration of recent findings, we conclude that epidrugs are promising treatments that could help to restore cisplatin sensitivity in resistant tumors, shedding light on potential avenues for better prognosis for the benefit of the patients.

Once upon a Testis: The Tale of Cyclic Nucleotide Phosphodiesterase in Testicular Cancers

Phosphodiesterases are key regulators that fine tune the intracellular levels of cyclic nucleotides, given their ability to hydrolyze cAMP and cGMP. They are critical regulators of cAMP/cGMP-mediated signaling pathways, modulating their downstream biological effects such as gene expression, cell proliferation, cell-cycle regulation but also inflammation and metabolic function. Recently, mutations in PDE genes have been identified and linked to human genetic diseases and PDEs have been demonstrated to play a potential role in predisposition to several tumors, especially in cAMP-sensitive tissues. This review summarizes the current knowledge and most relevant findings regarding the expression and regulation of PDE families in the testis focusing on PDEs role in testicular cancer development.

Testicular germ cell tumors: Genomic alternations and RAS-dependent signaling

Testicular germ cell tumors (TGCTs) are a common malignancy occurring in young adult men. The various genetic risk factors have been suggested to contribute to TGCT pathogenesis, however, they have a distinct mutational profile with a low rate of somatic point mutations, more frequent chromosomal gains, and aneuploidy. The most frequently mutated oncogenes in human cancers are RAS oncogenes, while their impact on testicular carcinogenesis and refractory disease is still poorly understood. In this mini-review, we summarize current knowledge on genetic alternations of RAS signaling-associated genes (the single nucleotide polymorphisms and point mutations) in this particular cancer type and highlight their link to chemotherapy resistance mechanisms. We also mention the impact of epigenetic changes on TGCT progression. Lastly, we propose a model for RAS-dependent signaling networks, regulation, cross-talks, and outcomes in TGCTs.

Single-cell transcriptome reveals cellular heterogeneity and lineage-specific regulatory changes of fibroblasts in post-traumatic urethral stricture

Fibroblast is the critical repair cell for urethral wound healing. The dysfunction of fibroblasts can lead to excessive fibrosis and hypertrophic scar, which eventually leads to post-traumatic urethral stricture. However, the fibroblast subpopulation and intercellular communication in urethral stricture remains poorly understood. Therefore, a comprehensive single-cell resolution transcript landscape of human PTUS needs to be reported. We performed single-cell RNA-sequencing of 13,411 cells from post-urethral stricture tissue and adjacent normal tissue. Unsupervised clustering, function enrichment analysis, cell trajectory construction and intercellular communication analysis were applied to explore the cellular microenvironment and intercellular communication at single-cell level. We found that there is highly cell heterogeneity in urethral stricture tissue, which includes 11 cell lineages based on the cell markers. We identified the molecular typing of fibroblasts and indicated the key fibroblast subpopulations in the process of fibrogenesis during urethral stricture. The intercellular communication between fibroblasts and vascular endothelial cells was identified. As an important bridge in the communication, integrins may be a potential therapeutic target for post-traumatic urethral stricture. In conclusion, this study reveals the cellular heterogeneity and lineage-specific regulatory changes of fibroblasts in post-traumatic urethral stricture, thereby providing new insights and potential genes for post-traumatic urethral stricture treatment.

Genomic Characterization of Prostatic Basal Cell Carcinoma

Basal cell carcinoma (BCC) of the prostate is a rare tumor. Compared with the more common acinar adenocarcinoma (AAC) of the prostate, BCCs show features of basal cell differentiation and are thought to be biologically distinct from AAC. The spectrum of molecular alterations of BCC has not been comprehensively described, and genomic studies are lacking. Herein, whole genome sequencing was performed on archival formalin-fixed, paraffin-embedded specimens of two cases with BCC. Prostatic BCCs were characterized by an overall low copy number and mutational burden. Recurrent copy number loss of chromosome 16 was observed. In addition, putative driver gene alterations in KIT, DENND3, PTPRU, MGA, and CYLD were identified. Mechanistically, depletion of the CYLD protein resulted in increased proliferation of prostatic basal cells in vitro. Collectively, these studies show that prostatic BCC displays distinct genomic alterations from AAC and highlight a potential role for loss of chromosome 16 in the pathogenesis of this rare tumor type.

Germline stem cells in human

The germline cells are essential for the propagation of human beings, thus essential for the survival of mankind. The germline stem cells, as a unique cell type, generate various states of germ stem cells and then differentiate into specialized cells, spermatozoa and ova, for producing offspring, while self-renew to generate more stem cells. Abnormal development of germline stem cells often causes severe diseases in humans, including infertility and cancer. Primordial germ cells (PGCs) first emerge during early embryonic development, migrate into the gentile ridge, and then join in the formation of gonads. In males, they differentiate into spermatogonial stem cells, which give rise to spermatozoa via meiosis from the onset of puberty, while in females, the female germline stem cells (FGSCs) retain stemness in the ovary and initiate meiosis to generate oocytes. Primordial germ cell-like cells (PGCLCs) can be induced in vitro from embryonic stem cells or induced pluripotent stem cells. In this review, we focus on current advances in these embryonic and adult germline stem cells, and the induced PGCLCs in humans, provide an overview of molecular mechanisms underlying the development and differentiation of the germline stem cells and outline their physiological functions, pathological implications, and clinical applications.

Different Expression Patterns of Metabolic Reprogramming Proteins in Testicular Germ Cell Cancer

Metabolic reprogramming is an emerging hallmark of cancer, involving the overexpression of metabolism-related proteins, such as glucose and monocarboxylate transporters and intracellular glycolytic enzymes. The biology of testicular germ cell tumors (TGCTs) is very complex, and although their metabolic profile has been scantily explored, some authors have recently reported that the metabolic rewiring of cancer cells resulted in an association with aggressive clinicopathological characteristics. In this study we have investigated, by immunohistochemical analysis, the expression of key proteins sustaining the hyperglycolytic phenotype in pure seminoma (SE, nr. 35), pure embryonal carcinoma (EC, nr. 17) tissues samples, and normal testes (nr. 5). GLUT1, CD44, PFK-1, MCT1, MCT4, LDH-A, and PDH resulted in more expression in EC cells compared to SE cells. TOM20 was more expressed in SE than in EC. GLUT1, MCT1, and MCT4 expression showed a statistically significant association with SE histology, while for EC, the association resulted in being significant only for GLUT1 and MCT4. Finally, we observed that EC resulted as negative for p53, suggesting that the GLUT1 and MTC overexpression observed in EC could be also attributed to p53 downregulation. In conclusion, our findings evidenced that EC exhibits a higher expression of markers of active aerobic glycolysis compared to SE, suggesting that the aggressive phenotype is associated with a higher glycolytic rate. These data corroborate the emerging evidence on the involvement of metabolic reprogramming in testicular malignancies as well, highlighting that the metabolic players should be explored in the future as promising therapeutic targets.

Dynamic regulation of P-TEFb by 7SK snRNP is integral to the DNA damage response to regulate chemotherapy sensitivity

Testicular germ cell tumors and closely related embryonal stem cells are exquisitely sensitive to cisplatin, a feature thought to be linked to their pluripotent state and p53 status. It remains unclear whether and how cellular state is coordinated with p53 to confer cisplatin sensitivity. Here, we report that positive transcription elongation factor b (P-TEFb) determines cell fate upon DNA damage. We find that cisplatin rapidly activates P-TEFb by releasing it from inhibitory 7SK small nuclear ribonucleoprotein complex. P-TEFb directly phosphorylates pluripotency factor estrogen-related receptor beta (ESRRB), and induces its proteasomal degradation to enhance pro-survival glycolysis. On the other hand, P-TEFb is required for the transcription of a substantial portion of p53 target genes, triggering cell death during prolonged cisplatin treatment. These results reveal previously underappreciated roles of P-TEFb to coordinate the DNA damage response. We discuss the implications for using P-TEFb inhibitors to treat cancer and ameliorate cisplatin-induced ototoxicity.

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P-TEFb regulates pro-survival and pro-death pathways during DNA damage response

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P-TEFb promotes ESRRB proteasomal degradation to enhance pro-survival glycolysis

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P-TEFb induces a substantial portion of p53 target genes to trigger cell death

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Chemical inhibitors of P-TEFb blocks cisplatin- or UV-induced cell death

Mapk activation drives male and female mouse teratocarcinomas from late PGCs

Germ cell tumors (GCTs) are rare tumors that can develop in both sexes, peaking in adolescents. To understand the mechanisms that underlie germ cell transformation, we established a GCT mouse model carrying germ cell-specific BRafV600E mutation with or without heterozygous Pten deletion. Both male and female mice developed monolateral teratocarcinomas containing embryonal carcinoma (EC) cells that showed an aggressive phenotype and metastatic ability. Germ cell transformation started in fetal gonads and progressed after birth leading to gonadal invasion. Early postnatal testes showed foci of tumor transformation, while ovaries showed increased number of follicles, multi-ovular follicles (MOFs) and scattered metaphase I oocytes containing follicles. Our results indicate that Mapk over-activation in fetal germ cells of both sexes can expand their proliferative window leading to neoplastic transformation and metastatic behavior.

MicroRNAs in Differentiation of Embryoid Bodies and the Teratoma Subtype of Testicular Cancer

BACKGROUND

Testicular germ cell tumours (TGCTs) are the most frequent tumour type among young, adult men. TGCTs can be efficiently treated, but metastases of the teratoma subtype, for which there are no circulating biomarkers, represent a challenge.

MATERIALS AND METHODS

Global microRNA expression in teratoma tissue and embryoid bodies was assessed using next-generation sequencing. Levels of microRNAs identified as potential biomarkers were obtained from serum of patients with teratoma and matched healthy men.

RESULTS

We identified miR-222-5p, miR-200a-5p, miR-196b-3p and miR-454-5p as biomarker candidates from the tumour tissue and embryoid body screening but the expression of these microRNAs was very low in serum and not statistically different between patients and controls. miR-375-3p was highly expressed, being highest in patients with teratoma (p=0.012) but the levels of expression in serum from these patients and healthy controls overlapped. miR-371a-3p was not expressed in serum from patients with pure teratoma, only in patients with mixed tumours.

CONCLUSION

The microRNA profiles of the teratoma subtype of TGCT and embryoid bodies were obtained and assessed for candidate circulating biomarkers, but none with high sensitivity and specificity for teratoma were identified in our study. We conclude that neither the proposed teratoma marker miR-375-3p nor miR-371a-3p are suitable as circulating teratoma markers.

Diverse Roles and Targets of miRNA in the Pathogenesis of Testicular Germ Cell Tumour

Testicular germ cell tumour (TGCT) is the most common cancer type among young adults in many parts of the world. Although the pathogenesis of TGCT is not well understood, the involvement of heritable components is evident, and the risk is polygenic. Genome-wide association studies have so far found 78 susceptibility loci for TGCT, and many of the loci are in non-coding regions indicating the involvement of non-coding RNAs in TGCT pathogenesis. MicroRNAs (miRNAs), a class of non-coding RNAs, have emerged as important gene regulators at the post-transcriptional level. They are crucial in controlling many cellular processes, such as proliferation, differentiation, and apoptosis, and an aberrant miRNA expression may contribute to the pathogenesis of several cancers, including TGCT. In support of this notion, several studies reported differential expression of miRNAs in TGCTs. We previously demonstrated that miRNAs were the most common group of small non-coding RNAs in TGCTs, and several functional studies of miRNAs in TGCTs suggest that they may act as either oncogene or tumour suppressors. Moreover, individual miRNA targets and downstream pathways in the context of TGCT development have been explored. In this review, we will focus on the diverse roles and targets of miRNAs in TGCT pathogenesis.

OUP accepted manuscript

The pathways of gametogenesis encompass elaborate cellular specialization accompanied by precise partitioning of the genome content in order to produce fully matured spermatozoa and oocytes. Transcription factors are an important class of molecules that function in gametogenesis to regulate intrinsic gene expression programs, play essential roles in specifying (or determining) germ cell fate and assist in guiding full maturation of germ cells and maintenance of their populations. Moreover, in order to reinforce or redirect cell fate in vitro, it is transcription factors that are most frequently induced, over-expressed or activated. Many reviews have focused on the molecular development and genetics of gametogenesis, in vivo and in vitro, in model organisms and in humans, including several recent comprehensive reviews: here, we focus specifically on the role of transcription factors. Recent advances in stem cell biology and multi-omic studies have enabled deeper investigation into the unique transcriptional mechanisms of human reproductive development. Moreover, as methods continually improve, in vitro differentiation of germ cells can provide the platform for robust gain- and loss-of-function genetic analyses. These analyses are delineating unique and shared human germ cell transcriptional network components that, together with somatic lineage specifiers and pluripotency transcription factors, function in transitions from pluripotent stem cells to gametes. This grand theme review offers additional insight into human infertility and reproductive disorders that are linked predominantly to defects in the transcription factor networks and thus may potentially contribute to the development of novel treatments for infertility.

The tumour suppressor CCDC6 is involved in ROS tolerance and neoplastic transformation by evading ferroptosis

Coiled-coil domain containing 6 (CCDC6) is a tumour suppressor gene involved in apoptosis and DNA damage response. CCDC6 is known to be functionally impaired upon gene fusions, somatic mutations, and altered protein turnover in several tumours. Testicular germ cell tumours are among the most common malignancies in young males. Despite the high cure rate, achieved through chemotherapy and/or surgery, drug resistance can still occur. In a human cellular model of testis Embryonal Carcinoma, the deficiency of CCDC6 was associated with defects in DNA repair via homologous recombination and sensitivity to PARP1/2 inhibitors. Same data were obtained in a panel of murine testicular cell lines, including Sertoli, Spermatogonia and Spermatocytes. In these cells, upon oxidative damage exposure, the absence of CCDC6 conferred tolerance to reactive oxygen species affecting regulated cell death pathways by apoptosis and ferroptosis. At molecular level, the loss of CCDC6 was associated with an enhancement of the xCT/SLC7A11 cystine antiporter expression which, by promoting the accumulation of ROS, interfered with the activation of ferroptosis pathway. In conclusion, our data suggest that the CCDC6 downregulation could aid the testis germ cells to be part of a pro-survival pathway that helps to evade the toxic effects of endogenous oxidants contributing to testicular neoplastic growth. Novel therapeutic options will be discussed.

Recent advances in testicular germ cell tumours

Testicular germ cell tumours (TGCTs) are the most common solid tumours in young men and have an excellent overall cure rate and prognosis. In most patients, localised disease is cured by surgery alone, and a minority of patients receive short-course adjuvant chemotherapy to reduce the risk of further relapse. Also, in about 80% of patients, metastatic disease can be cured by systemic cisplatin-based chemotherapy. Unfortunately, for a proportion of patients, the disease exhibits platinum resistance and relapse occurs. Despite further lines of systemic treatment, cure can be difficult to achieve in these patients and ultimately about 20% of them will die from disease progression. Addressing the mechanisms underpinning platinum resistance is critical to improving the survival and chances of cure for these patients. This review describes the latest advances in TGCT research, focusing on the identification of novel biomarkers, genetic characteristics and exploring novel treatments.

Testicular Tumors: A Contemporary Update on Morphologic, Immunohistochemical and Molecular Features

Testicular tumors are incredibly diverse and one of the most challenging areas in surgical pathology. Because of the rarity and overlapping features with numerous entities occurring in the testis and paratestis, these tumors pose a diagnostic challenge even to the most experienced general pathologists. In 2016, the latest "World Health Organization (WHO) classification of testicular tumors" was released, which incorporated several updates to the previous 2004 classification system. These updates involved several entities, including germ cell tumors, sex cord-stromal tumors, tumors containing both germ cells and sex-cord stromal cells, a miscellaneous group of testicular tumors and paratesticular tumors. In addition, significant changes were also introduced in the 2018 AJCC TNM staging (8th edition) regarding testicular tumors. The germ cell tumors are divided into 2 major groups; tumors derived from germ cell neoplasia in situ (GCNIS) and those unrelated to GCNIS. The GCNIS associated tumors include seminomatous and nonseminomatous germ cell tumors, which constitute a heterogeneous group of tumors. Non-GCNIS-associated tumors include prepubertal-type teratoma, prepubertal yolk sac tumor, mixed prepubertal-type teratoma and yolk sac tumor and spermatocytic seminoma. In the sex cord-stromal category, the tumors are classified based on their cells of origin. Most are Leydig cell tumors and Sertoli cell tumors; however, several mixed and diverse entities based on cell types are included in this group. Gonadoblastoma is the only tumor in the mixed germ cell and sex cord-stromal tumor category. Because of recent advances in molecular techniques, abundant new genetic information has emerged which helped classify the tumors based on the molecular alterations and provided insights into the tumor pathogenesis. This review focused on the updates related to testicular germ cell tumors and sex cord-stromal tumors and described the morphologic, immunohistochemical and molecular characteristics with an aim to provide a practical diagnostic approach and an update on relevant recent molecular advances.

Association Between FSIP2 Mutation and an Improved Efficacy of Immune Checkpoint Inhibitors in Patients With Skin Cutaneous Melanoma

Background

Immune checkpoint inhibitors (ICIs) have shown remarkable success in treating skin cutaneous melanoma (SKCM); however, the response to treatment varies greatly between patients. Considering that the efficacy of ICI treatment is influenced by many factors, we selected the Fibrosheath interacting protein 2 (FSIP2) gene and systematically analyzed its potential to predict the efficacy of ICI treatment.

Methods

Patient data were collected from an ICI treatment cohort (n = 120) and a The Cancer Genome Atlas (TCGA)-SKCM cohort (n = 467). The data were divided into an FSIP2-mutant (MT) group and FSIP2-wild-type (WT) group according to FSIP2 mutation status. In this study, we analyzed the patients' overall survival rate, tumor mutational burden (TMB), neoantigen load (NAL), copy number variation (CNV), cell infiltration data and immune-related genes. We used gene set enrichment analysis (GSEA) to delineate biological pathways and processes associated with the efficacy of immunotherapy.

Results

The efficacy of ICI treatment of SKCM patients with FSIP2 mutation was significantly better than that of patients without FSIP2 mutation. The patients in the FSIP2-MT group had higher tumor immunogenicity and lower regulatory T cell (Treg) infiltration. Results of GSEA showed that pathways related to tumor progression (MAPK and FGFR), immunomodulation, and IL-2 synthesis inhibition were significantly downregulated in the FSIP2-MT group.

Conclusion

Our research suggests that the FSIP2 gene has the potential to predict the efficacy of ICI treatment. The high tumor immunogenicity and low Treg levels observed may be closely related to the fact that patients with FSIP2-MT can benefit from ICI treatment.

Testicular germ cell tumors arise in the absence of sex-specific differentiation

In response to signals from the embryonic testis, the germ cell intrinsic factor NANOS2 coordinates a transcriptional program necessary for the differentiation of pluripotent-like primordial germ cells toward a unipotent spermatogonial stem cell fate. Emerging evidence indicates that genetic risk factors contribute to testicular germ cell tumor initiation by disrupting sex-specific differentiation. Here, using the 129.MOLF-Chr19 mouse model of testicular teratomas and a NANOS2 reporter allele, we report that the developmental phenotypes required for tumorigenesis, including failure to enter mitotic arrest, retention of pluripotency and delayed sex-specific differentiation, were exclusive to a subpopulation of germ cells failing to express NANOS2. Single-cell RNA sequencing revealed that embryonic day 15.5 NANOS2-deficient germ cells and embryonal carcinoma cells developed a transcriptional profile enriched for MYC signaling, NODAL signaling and primed pluripotency. Moreover, lineage-tracing experiments demonstrated that embryonal carcinoma cells arose exclusively from germ cells failing to express NANOS2. Our results indicate that NANOS2 is the nexus through which several genetic risk factors influence tumor susceptibility. We propose that, in the absence of sex specification, signals native to the developing testis drive germ cell transformation.

Germline and Somatic Genetic Variants in the p53 Pathway Interact to Affect Cancer Risk, Progression, and Drug Response

Insights into oncogenesis derived from cancer susceptibility loci (SNP) hold the potential to facilitate better cancer management and treatment through precision oncology. However, therapeutic insights have thus far been limited by our current lack of understanding regarding both interactions of these loci with somatic cancer driver mutations and their influence on tumorigenesis. For example, although both germline and somatic genetic variation to the p53 tumor suppressor pathway are known to promote tumorigenesis, little is known about the extent to which such variants cooperate to alter pathway activity. Here we hypothesize that cancer risk-associated germline variants interact with somatic TP53 mutational status to modify cancer risk, progression, and response to therapy. Focusing on a cancer risk SNP (rs78378222) with a well-documented ability to directly influence p53 activity as well as integration of germline datasets relating to cancer susceptibility with tumor data capturing somatically-acquired genetic variation provided supportive evidence for this hypothesis. Integration of germline and somatic genetic data enabled identification of a novel entry point for therapeutic manipulation of p53 activities. A cluster of cancer risk SNPs resulted in increased expression of prosurvival p53 target gene KITLG and attenuation of p53-mediated responses to genotoxic therapies, which were reversed by pharmacologic inhibition of the prosurvival c-KIT signal. Together, our results offer evidence of how cancer susceptibility SNPs can interact with cancer driver genes to affect cancer progression and identify novel combinatorial therapies. SIGNIFICANCE: These results offer evidence of how cancer susceptibility SNPs can interact with cancer driver genes to affect cancer progression and present novel therapeutic targets.

Curing Cancer: Lessons from a Prototype

Simple Summary

Germ cell tumor of the testis (TGCT) teaches us that to cure cancer, we need to acquire and apply proper biological insight and clinical acumen. In 1946, about 90% of patients with metastatic TGCT died within the first year of diagnosis. Today, over 90% of the same patients are curable. This complete reversal in the cure rate of TGCT is not because we have designed better drugs (we have not), but because we have learned how to use the same drugs in the right patients under the right settings. Importantly, TGCT is a prototype stem cell tumor that may hold the key to unlocking the origin of cancers, thereby enhancing our understanding of cancer and improving the cure and care of patients with cancer.

Abstract

Germ cell tumor of the testis (TGCT) is a remarkably curable solid tumor even when it is widely metastatic and patently heterogeneous. It provides invaluable clues about the origin and nature of metastasis and heterogeneity, cancer dormancy and late recurrence, drug sensitivity and resistance, tumor immunity, and spontaneous remission that would enable us to enhance the cure and improve the care of patients with other currently intractable solid tumors. After all, germ cells are primeval stem cells and TGCT are a perfect stem cell tumor for us to investigate a stem cell versus genetic origin of cancer. In many respects, TGCT is a prototype stem cell tumor that will enable us to elucidate the role of differentiation versus dedifferentiation in the evolution of a complex mixed tumor. It will help us decipher relevance of the genome versus the epi-genome in a progenitor cancer stem cell versus a progeny differentiated cancer cell. Importantly, clarification of a cellular context versus the genetic makeup in cancer has immense clinical implications. We postulate a unified theory of cancer derived from seminal TGCT research to improve personalized cancer care. Contrary to current norms and conventional wisdom, we propose that when it concerns a complex rather than simple cancer and a mixed rather than pure tumor (which is practically all solid tumors) multimodal therapy trumps targeted therapy and integrated medicine overrides precision medicine.

Contributions of Flow Cytometry to the Molecular Study of Spermatogenesis in Mammals

Mammalian testes are very heterogeneous organs, with a high number of different cell types. Testicular heterogeneity, together with the lack of reliable in vitro culture systems of spermatogenic cells, have been an obstacle for the characterization of the molecular bases of the unique events that take place along the different spermatogenic stages. In this context, flow cytometry has become an invaluable tool for the analysis of testicular heterogeneity, and for the purification of stage-specific spermatogenic cell populations, both for basic research and for clinical applications. In this review, we highlight the importance of flow cytometry for the advances on the knowledge of the molecular groundwork of spermatogenesis in mammals. Moreover, we provide examples of different approaches to the study of spermatogenesis that have benefited from flow cytometry, including the characterization of mutant phenotypes, transcriptomics, epigenetic and genome-wide chromatin studies, and the attempts to establish cell culture systems for research and/or clinical aims such as infertility treatment.

Fluorescence In Situ Hybridization (FISH) Detection of Chromosomal 12p Anomalies in Testicular Germ Cell Tumors

Gains of genetic material or internal rearrangements of chromosome 12p, including 12p overrepresentation or isochromosome 12p [i(12p)], are observed in virtually all germ cell tumors (GCT), in all histologic subtypes, and from various body locations. The chromosomal region involved in these alterations contains the growth and survival promoting oncogene KRAS (12p12.1). Gains or rearrangements of 12p characterize GCT from in situ to chemoresistant stages. Fluorescence in situ hybridization (FISH) detection of chromosome 12p anomalies is a sensitive and specific test for the diagnosis of germ cell tumors. Here we provide a detailed protocol for FISH detection of isochromosome 12p and chromosome 12p overrepresentation. The method is helpful for diagnosis of germ cell origin, and for selection of patients who may benefit from cisplatin-based chemotherapy.

A Genetically Engineered Mouse Model of Malignant Testicular Germ Cell Tumors

Testicular germ cell tumors (TGCTs) are among the most curable solid cancers and are typically highly responsive to conventional DNA-damaging chemotherapies, even in patients with metastatic disease. It has therefore been of great interest to understand the basis for the unique chemosensitivity of these cancers, which is linked to the DNA damage sensitivity of their cancer stem cells. TGCTs have been difficult to study in the mouse, however, since most of the existing mouse models develop benign teratomas that are unlike the malignant TGCTs that afflict most testicular cancer patients. We describe here methods for generating a TGCT mouse model that closely resembles the malignant, metastatic disease observed in men with testicular cancer, and additionally include methods for analyzing the cancer stems cells and responses to chemotherapeutics in these murine TGCTs.

Establishment and characterisation of testicular cancer patient-derived xenograft models for preclinical evaluation of novel therapeutic strategies

Testicular cancer (TC) is the most common solid tumour in young men. While cisplatin-based chemotherapy is highly effective in TC patients, chemoresistance still accounts for 10% of disease-related deaths. Pre-clinical models that faithfully reflect patient tumours are needed to assist in target discovery and drug development. Tumour pieces from eight TC patients were subcutaneously implanted in NOD scid gamma (NSG) mice. Three patient-derived xenograft (PDX) models of TC, including one chemoresistant model, were established containing yolk sac tumour and teratoma components. PDX models and corresponding patient tumours were characterised by H&E, Ki-67 and cyclophilin A immunohistochemistry, showing retention of histological subtypes over several passages. Whole-exome sequencing, copy number variation analysis and RNA-sequencing was performed on these TP53 wild type PDX tumours to assess the effects of passaging, showing high concordance of molecular features between passages. Cisplatin sensitivity of PDX models corresponded with patients' response to cisplatin-based chemotherapy. MDM2 and mTORC1/2 targeted drugs showed efficacy in the cisplatin sensitive PDX models. In conclusion, we describe three PDX models faithfully reflecting chemosensitivity of TC patients. These models can be used for mechanistic studies and pre-clinical validation of novel therapeutic strategies in testicular cancer.

Molecular signatures identified by integrating gene expression and methylation in non-seminoma and seminoma of testicular germ cell tumours

Testicular germ cell tumours (TGCTs) are the most common cancer in young male adults (aged 15 to 40). Unlike most other cancer types, identification of molecular signatures in TGCT has rarely reported. In this study, we developed a novel integrative analysis framework to identify co-methylated and co-expressed genes [mRNAs and microRNAs (miRNAs)] modules in two TGCT subtypes: non-seminoma (NSE) and seminoma (SE). We first integrated DNA methylation and mRNA/miRNA expression data and then used a statistical method, CoMEx (Combined score of DNA Methylation and Expression), to assess differentially expressed and methylated (DEM) genes/miRNAs. Next, we identified co-methylation and co-expression modules by applying WGCNA (Weighted Gene Correlation Network Analysis) tool to these DEM genes/miRNAs. The module with the highest average Pearson's Correlation Coefficient (PCC) after considering all pair-wise molecules (genes/miRNAs) included 91 molecules. By integrating both transcription factor and miRNA regulations, we constructed subtype-specific regulatory networks for NSE and SE. We identified four hub miRNAs (miR-182-5p, miR-520b, miR-520c-3p, and miR-7-5p), two hub TFs (MYC and SP1), and two genes (RECK and TERT) in the NSE-specific regulatory network, and two hub miRNAs (miR-182-5p and miR-338-3p), five hub TFs (ETS1, HIF1A, HNF1A, MYC, and SP1), and three hub genes (CDH1, CXCR4, and SNAI1) in the SE-specific regulatory network. miRNA (miR-182-5p) and two TFs (MYC and SP1) were common hubs of NSE and SE. We further examined pathways enriched in these subtype-specific networks. Our study provides a comprehensive view of the molecular signatures and co-regulation in two TGCT subtypes.

Incident testicular cancer in relation to using marijuana and smoking tobacco: A systematic review and meta-analysis of epidemiologic studies

BACKGROUND

Recent epidemiologic studies identified credible associations between marijuana smoking and risk of nonseminomatous testicular germ cell tumors (TGCTs), but did not distinguish exposure to cannabinoid compounds from exposure to other constituents of smoke.

METHODS

We implemented a systematic review of scholarly literature followed by random effects meta-analysis to quantitatively synthesize published data relating incident TGCT to each of 2 exposure histories: ever using marijuana, and ever smoking tobacco.

RESULTS

We identified four epidemiologic studies of marijuana use and 12 of tobacco smoking. Summary data concur with earlier reports of a specific association of marijuana use with nonseminoma, summary odds ratio [sOR] = 1.71 (95% confidence interval [CI] 1.12-2.60), and identify a positive association, sOR = 1.18 (95% CI 1.05-1.33), between tobacco smoking and all TGCT.

CONCLUSIONS

Available data accord with positive associations between incident TGCT and each exposure, implicating both cannabinoid compounds and other constituents of smoke. Etiologic interpretation awaits epidemiologic studies that assess associations between tobacco smoking and nonseminomatous TGCT, investigating not only these exposures but also both co-use of tobacco and marijuana and smoke-free sources of cannabinoids, while adequately evaluating potential confounding among all of these exposures.

Testicular cancer: Determinants of cisplatin sensitivity and novel therapeutic opportunities

Testicular cancer (TC) is the most common solid tumor among men aged between 15 and 40 years. TCs are highly aneuploid and the 12p isochromosome is the most frequent chromosomal abnormality. The mutation rate is of TC is low, with recurrent mutations in KIT and KRAS observed only at low frequency in seminomas. Overall cure rates are high, even in a metastatic setting, resulting from excellent cisplatin sensitivity of TCs. Factors contributing to the observed cisplatin sensitivity include defective DNA damage repair and a hypersensitive apoptotic response to DNA damage. Nonetheless, around 10-20% of TC patients with metastatic disease cannot be cured by cisplatin-based chemotherapy. Resistance mechanisms include downregulation of OCT4 and failure to induce PUMA and NOXA, elevated levels of MDM2, and hyperactivity of the PI3K/AKT/mTOR pathway. Several pre-clinical approaches have proven successful in overcoming cisplatin resistance, including specific targeting of PARP, MDM2 or AKT/mTOR combined with cisplatin. Finally, patient-derived xenograft models hold potential for mechanistic studies and pre-clinical validation of novel therapeutic strategies in TC. While clinical trials investigating targeted drugs have been disappointing, pre-clinical successes with chemotherapy and targeted drug combinations fuel the need for further investigation in clinical setting.

DNA replication machinery prevents Rad52-dependent single-strand annealing that leads to gross chromosomal rearrangements at centromeres

Homologous recombination between repetitive sequences can lead to gross chromosomal rearrangements (GCRs). At fission yeast centromeres, Rad51-dependent conservative recombination predominantly occurs between inverted repeats, thereby suppressing formation of isochromosomes whose arms are mirror images. However, it is unclear how GCRs occur in the absence of Rad51 and how GCRs are prevented at centromeres. Here, we show that homology-mediated GCRs occur through Rad52-dependent single-strand annealing (SSA). The rad52-R45K mutation, which impairs SSA activity of Rad52 protein, dramatically reduces isochromosome formation in rad51 deletion cells. A ring-like complex Msh2-Msh3 and a structure-specific endonuclease Mus81 function in the Rad52-dependent GCR pathway. Remarkably, mutations in replication fork components, including DNA polymerase α and Swi1/Tof1/Timeless, change the balance between Rad51-dependent recombination and Rad52-dependent SSA at centromeres, increasing Rad52-dependent SSA that forms isochromosomes. Our results uncover a role of DNA replication machinery in the recombination pathway choice that prevents Rad52-dependent GCRs at centromeres.

Primrose syndrome: Characterization of the phenotype in 42 patients

Primrose syndrome (PS; MIM# 259050) is characterized by intellectual disability (ID), macrocephaly, unusual facial features (frontal bossing, deeply set eyes, down‐slanting palpebral fissures), calcified external ears, sparse body hair and distal muscle wasting. The syndrome is caused by de novo heterozygous missense variants in ZBTB20. Most of the 29 published patients are adults as characteristics appear more recognizable with age. We present 13 hitherto unpublished individuals and summarize the clinical and molecular findings in all 42 patients. Several signs and symptoms of PS develop during childhood, but the cardinal features, such as calcification of the external ears, cystic bone lesions, muscle wasting, and contractures typically develop between 10 and 16 years of age. Biochemically, anemia and increased alpha‐fetoprotein levels are often present. Two adult males with PS developed a testicular tumor. Although PS should be regarded as a progressive entity, there are no indications that cognition becomes more impaired with age. No obvious genotype‐phenotype correlation is present. A subgroup of patients with ZBTB20 variants may be associated with mild, nonspecific ID. Metabolic investigations suggest a disturbed mitochondrial fatty acid oxidation. We suggest a regular surveillance in all adult males with PS until it is clear whether or not there is a truly elevated risk of testicular cancer.

Association of Inherited Pathogenic Variants in Checkpoint Kinase 2 (CHEK2) With Susceptibility to Testicular Germ Cell Tumors

Importance

Approximately 50% of the risk for the development of testicular germ cell tumors (TGCTs) is estimated to be heritable, but no mendelian TGCT predisposition genes have yet been identified. It is hypothesized that inherited pathogenic DNA repair gene (DRG) alterations may drive susceptibility to TGCTs.

Objective

To systematically evaluate the enrichment of germline pathogenic variants in the mendelian cancer predisposition DRGs in patients with TGCTs vs healthy controls.

Design, Setting, and Participants

A case-control enrichment analysis was performed from January 2016 to May 2018 to screen for 48 DRGs in 205 unselected men with TGCT and 27 173 ancestry-matched cancer-free individuals from the Exome Aggregation Consortium cohort in the discovery stage. Significant findings were selectively replicated in independent cohorts of 448 unselected men with TGCTs and 442 population-matched controls, as well as 231 high-risk men with TGCTs and 3090 ancestry-matched controls. Statistical analysis took place from January to May 2018.

Main Outcomes and Measures

Gene-level enrichment analysis of germline pathogenic variants in individuals with TGCTs relative to cancer-free controls.

Results

Among 205 unselected men with TGCTs (mean [SD] age, 33.04 [9.67] years), 22 pathogenic germline DRG variants, one-third of which were in CHEK2 (OMIM 604373), were identified in 20 men (9.8%; 95% CI, 6.1%-14.7%). Unselected men with TGCTs were approximately 4 times more likely to carry germline loss-of-function CHEK2 variants compared with cancer-free individuals from the Exome Aggregation Consortium cohort (odds ratio [OR], 3.87; 95% CI, 1.65-8.86; nominal P = .006; q = 0.018). Similar enrichment was also seen in an independent cohort of 448 unselected Croatian men with TGCTs (mean [SD] age, 31.98 [8.11] years) vs 442 unselected Croatian men without TGCTs (at least 50 years of age at time of sample collection) (OR, >1.4; P = .03) and 231 high-risk men with TGCTs (mean [SD] age, 31.54 [9.24] years) vs 3090 men (all older than 50 years) from the Penn Medicine Biobank (OR, 6.30; 95% CI, 2.34-17.31; P = .001). The low-penetrance CHEK2 variant (p.Ile157Thr) was found to be a Croatian founder TGCT risk variant (OR, 3.93; 95% CI, 1.53-9.95; P = .002). Individuals with the pathogenic CHEK2 loss-of-function variants developed TGCTs 6 years earlier than individuals with CHEK2 wild-type alleles (5.95 years; 95% CI, 1.48-10.42; P = .009).

Conclusions and Relevance

This multicenter case-control analysis of men with or without TGCTs provides evidence for CHEK2 as a novel moderate-penetrance TGCT susceptibility gene, with potential clinical utility. In addition to highlighting DNA-repair deficiency as a potential mechanism driving TGCT susceptibility, this analysis also provides new avenues to explore management strategies and biological investigations for high-risk individuals.

MicroRNA and transcription factor co-regulatory networks and subtype classification of seminoma and non-seminoma in testicular germ cell tumors

Recent studies have revealed that feed-forward loops (FFLs) as regulatory motifs have synergistic roles in cellular systems and their disruption may cause diseases including cancer. FFLs may include two regulators such as transcription factors (TFs) and microRNAs (miRNAs). In this study, we extensively investigated TF and miRNA regulation pairs, their FFLs, and TF-miRNA mediated regulatory networks in two major types of testicular germ cell tumors (TGCT): seminoma (SE) and non-seminoma (NSE). Specifically, we identified differentially expressed mRNA genes and miRNAs in 103 tumors using the transcriptomic data from The Cancer Genome Atlas. Next, we determined significantly correlated TF-gene/miRNA and miRNA-gene/TF pairs with regulation direction. Subsequently, we determined 288 and 664 dysregulated TF-miRNA-gene FFLs in SE and NSE, respectively. By constructing dysregulated FFL networks, we found that many hub nodes (12 out of 30 for SE and 8 out of 32 for NSE) in the top ranked FFLs could predict subtype-classification (Random Forest classifier, average accuracy ≥90%). These hub molecules were validated by an independent dataset. Our network analysis pinpointed several SE-specific dysregulated miRNAs (miR-200c-3p, miR-25-3p, and miR-302a-3p) and genes (EPHA2, JUN, KLF4, PLXDC2, RND3, SPI1, and TIMP3) and NSE-specific dysregulated miRNAs (miR-367-3p, miR-519d-3p, and miR-96-5p) and genes (NR2F1 and NR2F2). This study is the first systematic investigation of TF and miRNA regulation and their co-regulation in two major TGCT subtypes.

Dual mTORC1/2 Inhibition Sensitizes Testicular Cancer Models to Cisplatin Treatment

Testicular cancer is the most common cancer type among young men. Despite highly effective cisplatin-based chemotherapy, around 20% of patients with metastatic disease will still die from the disease. The aim of this study was to explore the use of kinase inhibitors to sensitize testicular cancer cells to cisplatin treatment. Activation of kinases, including receptor tyrosine kinases and downstream substrates, was studied in five cisplatin-sensitive or -resistant testicular cancer cell lines using phospho-kinase arrays and Western blotting. The phospho-kinase array showed AKT and S6 to be among the top phosphorylated proteins in testicular cancer cells, which are part of the PI3K/AKT/mTORC pathway. Inhibitors of most active kinases in the PI3K/AKT/mTORC pathway were tested using apoptosis assays and survival assays. Two mTORC1/2 inhibitors, AZD8055 and MLN0128, strongly enhanced cisplatin-induced apoptosis in all tested testicular cancer cell lines. Inhibition of mTORC1/2 blocked phosphorylation of the mTORC downstream proteins S6 and 4E-BP1. Combined treatment with AZD8055 and cisplatin led to reduced clonogenic survival of testicular cancer cells. Two testicular cancer patient-derived xenografts (PDX), either from a chemosensitive or -resistant patient, were treated with cisplatin in the absence or presence of kinase inhibitor. Combined AZD8055 and cisplatin treatment resulted in effective mTORC1/2 inhibition, increased caspase-3 activity, and enhanced tumor growth inhibition. In conclusion, we identified mTORC1/2 inhibition as an effective strategy to sensitize testicular cancer cell lines and PDX models to cisplatin treatment. Our results warrant further investigation of this combination therapy in the treatment of patients with testicular cancer with high-risk relapsed or refractory disease.

Integrated Molecular Characterization of Testicular Germ Cell Tumors

We studied 137 primary testicular germ cell tumors (TGCTs) using high-dimensional assays of genomic, epigenomic, transcriptomic, and proteomic features. These tumors exhibited high aneuploidy and a paucity of somatic mutations. Somatic mutation of only three genes achieved significance-KIT, KRAS, and NRAS-exclusively in samples with seminoma components. Integrated analyses identified distinct molecular patterns that characterized the major recognized histologic subtypes of TGCT: seminoma, embryonal carcinoma, yolk sac tumor, and teratoma. Striking differences in global DNA methylation and microRNA expression between histology subtypes highlight a likely role of epigenomic processes in determining histologic fates in TGCTs. We also identified a subset of pure seminomas defined by KIT mutations, increased immune infiltration, globally demethylated DNA, and decreased KRAS copy number. We report potential biomarkers for risk stratification, such as miRNA specifically expressed in teratoma, and others with molecular diagnostic potential, such as CpH (CpA/CpC/CpT) methylation identifying embryonal carcinomas.

Mechanisms of cisplatin sensitivity and resistance in testicular germ cell tumors

Testicular germ cell tumors (TGCTs) are a cancer pharmacology success story with a majority of patients cured even in the highly advanced and metastatic setting. Successful treatment of TGCTs is primarily due to the exquisite responsiveness of this solid tumor to cisplatin-based therapy. However, a significant percentage of patients are, or become, refractory to cisplatin and die from progressive disease. Mechanisms for both clinical hypersensitivity and resistance have largely remained a mystery despite the promise of applying lessons to the majority of solid tumors that are not curable in the metastatic setting. Recently, this promise has been heightened by the realization that distinct (and perhaps pharmacologically replicable) epigenetic states, rather than fixed genetic alterations, may play dominant roles in not only TGCT etiology and progression but also their curability with conventional chemotherapies. In this review, it discusses potential mechanisms of TGCT cisplatin sensitivity and resistance to conventional chemotherapeutics.

Molecular Basis of Cisplatin Resistance in Testicular Germ Cell Tumors

The emergence of cisplatin (CDDP) resistance is the main cause of treatment failure and death in patients with testicular germ cell tumors (TGCT), but its biologic background is poorly understood. To study the molecular basis of CDDP resistance in TGCT we prepared and sequenced CDDP-exposed TGCT cell lines as well as 31 primary patients' samples. Long-term exposure to CDDP increased the CDDP resistance 10 times in the NCCIT cell line, while no major resistance was achieved in Tera-2. Development of CDDP resistance was accompanied by changes in the cell cycle (increase in G1 and decrease in S-fraction), increased number of acquired mutations, of which 3 were present within ATRX gene, as well as changes in gene expression pattern. Copy number variation analysis showed, apart from obligatory gain of 12p, several other large-scale gains (chr 1, 17, 20, 21) and losses (chr X), with additional more CNVs found in CDDP-resistant cells (e.g., further losses on chr 1, 4, 18, and gain on chr 8). In the patients' samples, those who developed CDDP resistance and died of TGCT (2/31) showed high numbers of acquired aberrations, both SNPs and CNVs, and harbored mutations in genes potentially relevant to TGCT development (e.g., TRERF1, TFAP2C in one patient, MAP2K1 and NSD1 in another one). Among all primary tumor samples, the most commonly mutated gene was NSD1, affected in 9/31 patients. This gene encoding histone methyl transferase was also downregulated and identified among the 50 most differentially expressed genes in CDDP-resistant NCCIT cell line. Interestingly, 2/31 TGCT patients harbored mutations in the ATRX gene encoding a chromatin modifier that has been shown to have a critical function in sexual differentiation. Our research newly highlights its probable involvement also in testicular tumors. Both findings support the emerging role of altered epigenetic gene regulation in TGCT and CDDP resistance development.

Chromosome 12p Amplification in Triple-Negative/BRCA1-Mutated Breast Cancer Associates with Emergence of Docetaxel Resistance and Carboplatin Sensitivity

Taxanes are the mainstay of treatment in triple-negative breast cancer (TNBC), with de novo and acquired resistance limiting patient's survival. To investigate the genetic basis of docetaxel resistance in TNBC, exome sequencing was performed on matched TNBC patient-derived xenografts (PDX) sensitive to docetaxel and their counterparts that developed resistance in vivo upon continuous drug exposure. Most mutations, small insertions/deletions, and copy number alterations detected in the initial TNBC human metastatic samples were maintained after serial passages in mice and emergence of resistance. We identified a chromosomal amplification of chr12p in a human BRCA1-mutated metastatic sample and the derived chemoresistant PDX, but not in the matched docetaxel-sensitive PDX tumor. Chr12p amplification was validated in a second pair of docetaxel-sensitive/resistant BRCA1-mutated PDXs and after short-term docetaxel treatment in several TNBC/BRCA1-mutated PDXs and cell lines, as well as during metastatic recurrence in a patient with BRCA1-mutated breast cancer who had progressed on docetaxel treatment. Analysis of clinical data indicates an association between chr12p amplification and patients with TNBC/basal-like breast cancer, a BRCA1 mutational signature, and poor survival after chemotherapy. Detection of chr12p amplification in a cohort of TNBC PDX models was associated with an improved response to carboplatin. Our findings reveal tumor clonal dynamics during chemotherapy treatments and suggest that a preexisting population harboring chr12p amplification is associated with the emergence of docetaxel resistance and carboplatin responsiveness in TNBC/BRCA1-mutated tumors. SIGNIFICANCE: Chr12p copy number gains indicate rapid emergence of resistance to docetaxel and increased sensitivity to carboplatin, therefore sequential docetaxel/carboplatin treatment could improve survival in TNBC/BRCA1 patients. GRAPHICAL ABSTRACT: http://cancerres.aacrjournals.org/content/canres/79/16/4258/F1.large.jpg.

gr/gr deletion predisposes to testicular germ cell tumour independently from altered spermatogenesis: results from the largest European study

The association between impaired spermatogenesis and TGCT has stimulated research on shared genetic factors. Y chromosome-linked partial AZFc deletions predispose to oligozoospermia and were also studied in TGCT patients with controversial results. In the largest study reporting the association between gr/gr deletion and TGCT, sperm parameters were unknown. Hence, it remains to be established whether this genetic defect truly represents a common genetic link between TGCT and impaired sperm production. Our aim was to explore the role of the following Y chromosome-linked factors in the predisposition to TGCT: (i) gr/gr deletion in subjects with known sperm parameters; (ii) other partial AZFc deletions and, for the first time, the role of partial AZFc duplications; (iii) DAZ gene dosage variation. 497 TGCT patients and 2030 controls from two Mediterranean populations with full semen/andrological characterization were analyzed through a series of molecular genetic techniques. Our most interesting finding concerns the gr/gr deletion and DAZ gene dosage variation (i.e., DAZ copy number is different from the reference sequence), both conferring TGCT susceptibility. In particular, the highest risk was observed when normozoospermic TGCT and normozoospermic controls were compared (OR = 3.7; 95% CI = 1.5-9.1; p = 0.006 for gr/gr deletion and OR = 1.8; 95% CI = 1.1-3.0; p = 0.013 for DAZ gene dosage alteration). We report in the largest European study population the predisposing effect of gr/gr deletion to TGCT as an independent risk factor from impaired spermatogenesis. Our finding implies regular tumour screening/follow-up in male family members of TGCT patients with gr/gr deletion and in infertile gr/gr deletion carriers.

Clinicopathologic Characterization of Bilateral Testicular Germ Cell Tumors With Immunohistochemical Evaluation of Mismatch Repair and BRAF (V600E) Genes Mutations

The incidence of bilateral testicular germ cell tumor (TGCT) is 1% to 5%. Despite the high rate of treatment success, resistance to chemotherapy has a detrimental effect. Some studies found MMR and BRAF gene mutations to be associated with chemotherapy resistance, which has not been found by others. However, the role of microsatellite instability (MSI) and BRAF mutations in bilateral disease has not been investigated. In this article, we studied the clinicopathologic characteristics and immunohistochemical expressions of MMR and BRAF in 13 patients with bilateral TGCT. Bilateral tumors were found in 4% of patients in our data. The mean ages at the first and subsequent diagnoses were 26.9 and 28.3 years, respectively. Eleven patients had metachronous disease; and the mean period between both tumors was 4.9 years. Six had mixed GCTs (MGCT) initially and later developed contralateral seminoma, 3 had bilateral MGCTs; 1 initially had pure embryonal carcinoma and subsequently MGCT and finally, 1 patient had initial seminoma and contralateral germ cell neoplasia in situ only. Of the patients with synchronous GCT, 1 had a MGCT and contralateral non-seminoma and 1 had seminoma and contralateral MGCT. In metachronous cases, 40% and 78% had an initial and subsequent stage of pT1, respectively. Hormonal and/or metastatic recurrence was observed in 30% of metachronous tumors. Six patients received chemotherapy, including patients with metastasis. No progression occurred after therapy. MLH1, PMS2, MSH2, and MSH6 staining was retained in all tumors. No BRAF staining was found. In conclusion, we found no association between bilateral TGCT and the MMR/MSI pathway and that subsequent metachronous tumors behaved much more indolently.

Clonal analyses of refractory testicular germ cell tumors

Testicular germ cell tumors (TGCTs) are unique amongst solid tumors in terms of the high cure rates using chemotherapy for metastatic disease. Nevertheless, TGCTs still kill approximately 400 men per year, at a median age of 30 years, in the United States. This young age of mortality dramatically amplifies the impact of these deaths for the patients and their often young families. Furthermore the high cure rate makes it difficult to conduct further clinical trials of non curable disease. TGCTs are characterized by a marked aneuploidy and the presence of gain of chromosomal region 12p. Genomic testing may offer the ability to identify potentially lethal TGCTs at the time of initial diagnosis. However sequencing based studies have shown a paucity of somatic mutations in TGCT genomes including those that drive refractory disease. Furthermore these studies may be limited by genetic heterogeneity in primary tumors and the evolution of sub populations during disease progression. Herein we applied a systematic approach combining DNA content flow cytometry, whole genome copy number and whole exome sequence analyses to interrogate tumor heterogeneity in primary and metastatic refractory TGCTs. We identified both known and novel somatic copy number aberrations (12p, MDM2, and RHBDD1) and mutations (XRCC2, PIK3CA, RITA1) including candidate markers for platinum resistance that were present in a primary tumor of mixed histology and that remained after tandem autologous stem cell transplant.

The Warburg Effect Is Associated With Tumor Aggressiveness in Testicular Germ Cell Tumors

Testicular Germ Cell Tumors (TGCTs) are a rare group of neoplasms and the most common solid malignancy arising in young male adults. Despite the good response of these tumors to platinum-based chemotherapy, some patients are refractory to treatment and present poor clinical outcomes. During carcinogenesis and tumor development, cancer cells reprogram energy metabolism toward a hyper-glycolytic phenotype, an emerging hallmark of cancer. This phenomenon, known as the Warburg effect or aerobic glycolysis, involves overexpression of metabolism-related proteins, like glucose and monocarboxylate transporters, pH regulators and intracellular glycolytic enzymes. The metabolic profile of TGCTs is very little explored and, recently, this metabolic rewiring of cancer cells has been associated with aggressive clinicopathological characteristics of these tumors. The overexpression of monocarboxylate transporter 4 (MCT4) in TGCTs has been pointed out as a poor prognostic factor, as well as a promising therapeutic target. As a result, the main aim of the present study was to evaluate the prognostic value of key metabolism-related proteins in TGCTs. The immunohistochemical expressions of CD44 (as a monocarboxylate transporter chaperone), glucose transporter 1 (GLUT1), carbonic anhydrase IX (CAIX), hexokinase II (HKII) and lactate dehydrogenase V (LDHV) were evaluated in a series of 148 adult male patients with TGCTs and associated with clinicopathological parameters. In addition, paired normal tissues were also evaluated. The sample included 75 seminoma and 73 non-seminoma tumors. GLUT1 and CD44 expression was significantly increased in malignant samples when compared to paired normal samples. Conversely, HKII and LDHV expressions were significantly decreased in malignant samples. Concerning the clinicopathological values, CAIX expression was significantly associated with disease recurrence, while HKII expression was significantly associated with aggressive characteristics of TGCTs, including higher staging and non-seminoma histology. In conclusion, this study brings new insights on the metabolic characteristics of TGCTs, showing alterations in the expression of proteins related with the Warburg effect, as well as associations of the hyper-glycolytic and acid-resistant phenotype with aggressive clinicopathological parameters.

Origin, Composition, and Structure of the Supernumerary B Chromosome of Drosophila melanogaster

The number of chromosomes carried by an individual species is one of its defining characteristics. Some species, however, can also carry supernumerary chromosomes referred to as B chromosomes. B chromosomes were recently identified in a laboratory stock of Drosophila melanogaster-an established model organism with a wealth of genetic and genomic resources-enabling us to subject them to extensive molecular analysis. We isolated the B chromosomes by pulsed-field gel electrophoresis and determined their composition through next-generation sequencing. Although these B chromosomes carry no known euchromatic sequence, they are rich in transposable elements and long arrays of short nucleotide repeats, the most abundant being the uncharacterized AAGAT satellite repeat. Fluorescent in situ hybridization on metaphase chromosome spreads revealed this repeat is located on chromosome 4, strongly suggesting the origin of the B chromosomes is chromosome 4 Cytological and quantitative comparisons of signal intensity between chromosome 4 and the B chromosomes supports the hypothesis that the structure of the B chromosome is an isochromosome. We also report the identification of a new B chromosome variant in a related laboratory stock. This B chromosome has a similar repeat signature as the original but is smaller and much less prevalent. We examined additional stocks with similar genotypes and did not find B chromosomes, but did find these stocks lacked the AAGAT satellite repeat. Our molecular characterization of D. melanogaster B chromosomes is the first step toward understanding how supernumerary chromosomes arise from essential chromosomes and what may be necessary for their stable inheritance.

DNA methylation profiling as a tool for testicular germ cell tumors subtyping

AIM

Assess differential patterns of selected five genes' promoter methylation among testicular germ cell tumors (TGCT) subtypes.

MATERIALS & METHODS

 CRIPTO, HOXA9, MGMT, RASSF1A and SCGB3A1 promoter methylation levels were evaluated by quantitative methylation-specific PCR in 161 TGCT and 16 controls. Associations between clinicopathological parameters and promoter methylation levels were assessed, and receiver operating characteristics curve analysis was performed.

RESULTS

Promoter methylation of CRIPTO/HOXA9/SCGB3A1 panel and RASSF1A best discriminated between controls and nonseminomatous tumors or seminomas, respectively, whereas HOXA9/RASSF1A panel displayed the best discriminative performance between nonseminomatous tumor and seminomas. Significant differences in CRIPTO, MGMT and RASSF1A methylation levels were depicted between pure forms and matched mixed components of seminomas and embryonal carcinoma. HOXA9, RASSF1A and SCGB3A1 promoter methylation significantly associated with tumor stage.

CONCLUSION

Different combinations of five genes' promoter methylation levels discriminate among TGCT subtypes. Methylation patterns may also assist in identification of more clinically aggressive tumors.

Testicular Cancer Biomarkers: A Role for Precision Medicine in Testicular Cancer

Testicular germ cell tumors (TGCTs) represent the most common solid tumors among men aged 15 to 34 years. Fortunately, recent advances have made testicular cancer a highly curable disease. Despite the high cure rates, there are still several areas in testis cancer care where treatment decisions are controversial and guided only with clinical factors and historic serum tumor markers. Unfortunately, unlike other genitourinary malignancies, modern research techniques have not been widely tested or applied to germ cell tumors, perhaps as a result of excellent prognosis in this cohort of young men. Despite this, there remain numerous challenges and pitfalls in testis cancer care that need to be addressed. A reliable set of biomarkers could be extremely useful in helping risk-stratify patients, detect relapse early, guide surgical decision-making, and tailor follow-up. Current tumor markers (Alpha-fetoprotein, human chorionic gonadotrophin, and lactate dehydrogenase) have low accuracy and low sensitivity when used not only as diagnostic but also as prognostic and predictive markers. In twenty-first century medicine, there is a role for further prognostic stratification and the development of novel biomarkers that offer greater sensitivity and specificity for TGCTs. Despite the initial promising results, the majority of preclinical biomarkers do not, as yet have a proven validated role in clinical practice, and future prospective trials are needed to support and confirm the results of cohort studies. In this narrative review, we aimed to highlight the recent innovations in the development and implementation of novel testicular tumor markers and discuss their clinical applications and limitations in the management of this disease.

Large-scale Analysis Demonstrates Familial Testicular Cancer to have Polygenic Aetiology

Testicular germ cell tumour (TGCT) is the most common cancer in young men. Multiplex TGCT families have been well reported and analyses of population cancer registries have demonstrated a four- to eightfold risk to male relatives of TGCT patients. Early linkage analysis and recent large-scale germline exome analysis in TGCT cases demonstrate absence of major high-penetrance TGCT susceptibility gene(s). Serial genome-wide association study analyses in sporadic TGCT have in total reported 49 independent risk loci. To date, it has not been demonstrated whether familial TGCT arises due to enrichment of the same common variants underpinning susceptibility to sporadic TGCT or is due to shared environmental/lifestyle factors or disparate rare genetic TGCT susceptibility factors. Here we present polygenic risk score analysis of 37 TGCT susceptibility single-nucleotide polymorphisms in 236 familial and 3931 sporadic TGCT cases, and 12 368 controls, which demonstrates clear enrichment for TGCT susceptibility alleles in familial compared to sporadic cases (p=0.0001), with the majority of familial cases (84-100%) being attributable to polygenic enrichment. These analyses reveal TGCT as the first rare malignancy of early adulthood in which familial clustering is driven by the aggregate effects of polygenic variation in the absence of a major high-penetrance susceptibility gene.

PATIENT SUMMARY

To date, it has been unclear whether familial clusters of testicular germ cell tumour (TGCT) arise due to genetics or shared environmental or lifestyle factors. We present large-scale genetic analyses comparing 236 familial TGCT cases, 3931 isolated TGCT cases, and 12 368 controls. We show that familial TGCT is caused, at least in part, by presence of a higher dose of the same common genetic variants that cause susceptibility to TGCT in general.