Genetic Determinants of Cisplatin Resistance in Patients With Advanced Germ Cell Tumors

Treatment and Survival of Malignant Extracranial Germ Cell Tumours in the Paediatric Population: A Systematic Review and Meta-Analysis

OBJECTIVE

This systematic review and meta-analysis was performed to explore overall survival (OS) and event free survival (EFS) rates internationally over the past two decades and to define specific subgroups with inferior outcomes which may demand different treatment strategies.

METHODS

The search focused on malignant extracranial germ cell tumours (GCTs) in the paediatric population. The initial database search identified 12,556 articles; 32 articles were finally included in this review, comprising a total of 5095 patients.

RESULTS

The studies were heterogeneous, varying from single institution reports to large prospective trials. Older studies, describing eras where non-platinum-based chemotherapy regimens were used, showed clearly worse outcomes. Survival for stage I-II gonadal disease is excellent. On the other hand, patients with an initial alpha-fetoprotein (AFP) > 10,000 ng/mL or kU/L, age > 11 years and stage IV disease confer a survival disadvantage. For testicular disease in particular, lymphovascular invasion and certain histopathological subtypes, such as embryonal carcinoma (EC) and mixed malignant GCTs, survival is poorer. Survival data for sacrococcygeal and mediastinal GCTs show a heterogeneous distribution across studies in this review, independent of year of publication. Patients > 12 years presenting with a mediastinal GCT pose a subpopulation which fares worse than GCTs in other locations or age groups. This is independent of AFP levels, stage of disease or treatment protocol, and these patients may demand a different treatment strategy.

CONCLUSIONS

This review describes the heterogeneous nature of GCTs in different anatomical locations, impacting on stage at presentation, treatment modalities used and survival data. Despite this heterogeneity, in line with the current developmental biology-based classification system, subpopulations can be defined which have an inferior EFS and OS and where future research and more individualised treatment would help to improve survival.

The Enigmatic Role of TP53 in Germ Cell Tumours: Are We Missing Something?

The cure rate of germ cell tumours (GCTs) has significantly increased from the late 1970s since the introduction of cisplatin-based therapy, which to date remains the milestone for GCTs treatment. The exquisite cisplatin sensitivity has been mainly explained by the over-expression in GCTs of wild-type TP53 protein and the lack of TP53 somatic mutations; however, several other mechanisms seem to be involved, many of which remain still elusive. The findings about the role of TP53 in platinum-sensitivity and resistance, as well as the reported evidence of second cancers (SCs) in GCT patients treated only with surgery, suggesting a spectrum of cancer predisposing syndromes, highlight the need for a deepened understanding of the role of TP53 in GCTs. In the following report we explore the complex role of TP53 in GCTs cisplatin-sensitivity and resistance mechanisms, passing through several recent genomic studies, as well as its role in GCT patients with SCs, going through our experience of Center of reference for both GCTs and cancer predisposing syndromes.

Folate receptor α increases chemotherapy resistance through stabilizing MDM2 in cooperation with PHB2 that is overcome by MORAb-202 in gastric cancer

BACKGROUND

The main function of folate receptor α (FOLRα) has been considered to mediate intracellular folate uptake and induce tumor cell proliferation. Given the broad spectrum of expression among malignant tumors, including gastric cancer (GC) but not in normal tissue, FOLRα represents an attractive target for tumor-selective drug delivery. However, the efficacy of anti-FOLRα monoclonal antibodies (mAbs) has not been proved so far, with the reason for this failure remaining unclear, raising the need for a better understanding of FOLRα function.

METHODS

The distribution of FOLRα in GC cells was evaluated by immunohistochemistry. The impacts of FOLRα expression on the survival of GC patients and GC cell lines were examined with the Gene Expression Omnibus database and by siRNA of FOLRα. RNA-sequencing and Microarray analysis was conducted to identify the function of FOLRα. Proteins that interact with FOLRα were identified with shotgun LC-MS/MS. The antitumor efficacy of the anti-FOLRα mAb farletuzumab as well as the antibody-drug conjugate (ADC) consists of the farletuzumab and the tublin-depolymerizing agent eribulin (MORAb-202) was evaluated both in vitro and in vivo.

RESULTS

FOLRα was detected both at the cell membrane and in the cytoplasm. Shorter overall survival was associated with FOLRα expression in GC patients, whereas reduction of FOLRα attenuated cell proliferation without inducing cell death in GC cell lines. Transcriptomic and proteomic examinations revealed that the FOLRα-expressing cancer cells possess a mechanism of chemotherapy resistance supported by MDM2, and FOLRα indirectly regulates it through a chaperone protein prohibitin2 (PHB2). Although reduction of FOLRα brought about vulnerability for oxaliplatin by diminishing MDM2 expression, farletuzumab did not suppress the MDM2-mediated chemoresistance and cell proliferation in GC cells. On the other hand, MORAb-202 showed significant antitumor efficacy.

CONCLUSIONS

The ADC could be a more reasonable choice than mAb as a targeting agent for the FOLRα-expressing tumor.

Mechanisms of TP53 Pathway Inactivation in Embryonic and Somatic Cells-Relevance for Understanding (Germ Cell) Tumorigenesis

The P53 pathway is the most important cellular pathway to maintain genomic and cellular integrity, both in embryonic and non-embryonic cells. Stress signals induce its activation, initiating autophagy or cell cycle arrest to enable DNA repair. The persistence of these signals causes either senescence or apoptosis. Over 50% of all solid tumors harbor mutations in TP53 that inactivate the pathway. The remaining cancers are suggested to harbor mutations in genes that regulate the P53 pathway such as its inhibitors Mouse Double Minute 2 and 4 (MDM2 and MDM4, respectively). Many reviews have already been dedicated to P53, MDM2, and MDM4, while this review additionally focuses on the other factors that can deregulate P53 signaling. We discuss that P14^ARF (ARF) functions as a negative regulator of MDM2, explaining the frequent loss of ARF detected in cancers. The long non-coding RNA Antisense Non-coding RNA in the INK4 Locus (ANRIL) is encoded on the same locus as ARF, inhibiting ARF expression, thus contributing to the process of tumorigenesis. Mutations in tripartite motif (TRIM) proteins deregulate P53 signaling through their ubiquitin ligase activity. Several microRNAs (miRNAs) inactivate the P53 pathway through inhibition of translation. CCCTC-binding factor (CTCF) maintains an open chromatin structure at the TP53 locus, explaining its inactivation of CTCF during tumorigenesis. P21, a downstream effector of P53, has been found to be deregulated in different tumor types. This review provides a comprehensive overview of these factors that are known to deregulate the P53 pathway in both somatic and embryonic cells, as well as their malignant counterparts (i.e., somatic and germ cell tumors). It provides insights into which aspects still need to be unraveled to grasp their contribution to tumorigenesis, putatively leading to novel targets for effective cancer therapies.

Role of RNA N6-Methyladenosine Modification in Male Infertility and Genital System Tumors

Epigenetic alterations, particularly RNA methylation, play a crucial role in many types of disease development and progression. Among them, N6-methyladenosine (m6A) is the most common epigenetic RNA modification, and its important roles are not only related to the occurrence, progression, and aggressiveness of tumors but also affect the progression of many non-tumor diseases. The biological effects of RNA m6A modification are dynamically and reversibly regulated by methyltransferases (writers), demethylases (erasers), and m6A binding proteins (readers). This review summarized the current finding of the RNA m6A modification regulators in male infertility and genital system tumors and discussed the role and potential clinical application of the RNA m6A modification in spermatogenesis and male genital system tumors.

Molecular Biology of Pediatric and Adult Male Germ Cell Tumors

Simple Summary

Although testicular germ cell tumors (TGCTs) are rare pediatric malignancies, they are the most common malignancies in young adult men. The similarities and differences between TGCTs in adults and children, taking into account the clinic presentation, biology, and molecular changes, are underexplored. In this paper, we aim to provide an overview of the molecular aspects of TGCTs, drawing a parallel between the findings in adult and pediatric groups.

Abstract

Cancer is a leading cause of death by disease in children and the second most prevalent of all causes in adults. Testicular germ cell tumors (TGCTs) make up 0.5% of pediatric malignancies, 14% of adolescent malignancies, and are the most common of malignancies in young adult men. Although the biology and clinical presentation of adult TGCTs share a significant overlap with those of the pediatric group, molecular evidence suggests that TGCTs in young children likely represent a distinct group compared to older adolescents and adults. The rarity of this cancer among pediatric ages is consistent with our current understanding, and few studies have analyzed and compared the molecular basis in childhood and adult cancers. Here, we review the major similarities and differences in cancer genetics, cytogenetics, epigenetics, and chemotherapy resistance between pediatric and adult TGCTs. Understanding the biological and molecular processes underlying TGCTs may help improve patient outcomes, and fuel further investigation and clinical research in childhood and adult TGCTs.

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

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

WNT signalling in the normal human adult testis and in male germ cell neoplasms

STUDY QUESTION

Is WNT signalling functional in normal and/or neoplastic human male germ cells?

SUMMARY ANSWER

Regulated WNT signalling component synthesis in human testes indicates that WNT pathway function changes during normal spermatogenesis and is active in testicular germ cell tumours (TGCTs), and that WNT pathway blockade may restrict seminoma growth and migration.

WHAT IS KNOWN ALREADY

Regulated WNT signalling governs many developmental processes, including those affecting male fertility during early germ cell development at embryonic and adult (spermatogonial) ages in mice. In addition, although many cancers arise from WNT signalling alterations, the functional relevance and WNT pathway components in TGCT, including germ cell neoplasia in situ (GCNIS), are unknown.

STUDY DESIGN, SIZE, DURATION

The cellular distribution of transcripts and proteins in WNT signalling pathways was assessed in fixed human testis sections with normal spermatogenesis, GCNIS and seminoma (2-16 individuals per condition). Short-term (1-7 h) ligand activation and long-term (1-5 days) functional outcomes were examined using the well-characterised seminoma cell line, TCam-2. Pathway inhibition used siRNA or chemical exposures over 5 days to assess survival and migration.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The cellular localisation of WNT signalling components was determined using in situ hybridisation and immunohistochemistry on Bouin's- and formalin-fixed human testis sections with complete spermatogenesis or germ cell neoplasia, and was also assessed in TCam-2 cells. Pathway function tests included exposure of TCam-2 cells to ligands, small molecules and siRNAs. Outcomes were measured by monitoring beta-catenin (CTNNB1) intracellular localisation, cell counting and gap closure measurements.

MAIN RESULTS AND THE ROLE OF CHANCE

Detection of nuclear-localised beta-catenin (CTNNB1), and key WNT signalling components (including WNT3A, AXIN2, TCF7L1 and TCF7L2) indicate dynamic and cell-specific pathway activity in the adult human testis. Their presence in germ cell neoplasia and functional analyses in TCam-2 cells indicate roles for active canonical WNT signalling in TGCT relating to viability and migration. All data were analysed to determine statistical significance.

LARGE SCALE DATA

No large-scale datasets were generated in this study.

LIMITATIONS, REASONS FOR CAUTION

As TGCTs are rare and morphologically heterogeneous, functional studies in primary cancer cells were not performed. Functional analysis was performed with the only well-characterised, widely accepted seminoma-derived cell line.

WIDER IMPLICATIONS OF THE FINDINGS

This study demonstrated the potential sites and involvement of the WNT pathway in human spermatogenesis, revealing similarities with murine testis that suggest the potential for functional conservation during normal spermatogenesis. Evidence that inhibition of canonical WNT signalling leads to loss of viability and migratory activity in seminoma cells suggests that potential treatments using small molecule or siRNA inhibitors may be suitable for patients with metastatic TGCTs.

STUDY FUNDING AND COMPETING INTEREST(S)

This study was funded by National Health and Medical Research Council of Australia (Project ID 1011340 to K.L.L. and H.E.A., and Fellowship ID 1079646 to K.L.L.) and supported by the Victorian Government's Operational Infrastructure Support Program. None of the authors have any competing interests.

Targeting of Deregulated Wnt/β-Catenin Signaling by PRI-724 and LGK974 Inhibitors in Germ Cell Tumor Cell Lines

The majority of patients with testicular germ cell tumors (GCTs) can be cured with cisplatin-based chemotherapy. However, for a subset of patients present with cisplatin-refractory disease, which confers a poor prognosis, the treatment options are limited. Novel therapies are therefore urgently needed to improve outcomes in this challenging patient population. It has previously been shown that Wnt/β-catenin signaling is active in GCTs suggesting that its inhibitors LGK974 and PRI-724 may show promise in the management of cisplatin-refractory GCTs. We herein investigated whether LGK-974 and PRI-724 provide a treatment effect in cisplatin-resistant GCT cell lines. Taking a genoproteomic approach and utilizing xenograft models we found the increased level of β-catenin in 2 of 4 cisplatin-resistant (CisR) cell lines (TCam-2 CisR and NCCIT CisR) and the decreased level of β-catenin and cyclin D1 in cisplatin-resistant NTERA-2 CisR cell line. While the effect of treatment with LGK974 was limited or none, the NTERA-2 CisR exhibited the increased sensitivity to PRI-724 in comparison with parental cell line. Furthermore, the pro-apoptotic effect of PRI-724 was documented in all cell lines. Our data strongly suggests that a Wnt/β-catenin signaling is altered in cisplatin-resistant GCT cell lines and the inhibition with PRI-724 is effective in NTERA-2 CisR cells. Further evaluation of Wnt/β-catenin pathway inhibition in GCTs is therefore warranted.

Germ cell determination and the developmental origin of germ cell tumors

In each generation, the germline is tasked with producing somatic lineages that form the body, and segregating a population of cells for gametogenesis. During animal development, when do cells of the germline irreversibly commit to producing gametes? Integrating findings from diverse species, we conclude that the final commitment of the germline to gametogenesis - the process of germ cell determination - occurs after primordial germ cells (PGCs) colonize the gonads. Combining this understanding with medical findings, we present a model whereby germ cell tumors arise from cells that failed to undertake germ cell determination, regardless of their having colonized the gonads. We propose that the diversity of cell types present in these tumors reflects the broad developmental potential of migratory PGCs.

Between a Rock and a Hard Place: An Epigenetic-Centric View of Testicular Germ Cell Tumors

Simple Summary

This minireview focuses on the role of epigenetics in testicular cancer. A working model is developed that postulates that epigenetic features that drive testicular cancer malignancy also enable these tumors to be cured at a high rate with chemotherapy. Chemoresistance may occur by epigenetic uncoupling of malignancy and chemosensitivity, a scenario that may be amenable to epigenetic-based therapies.

Abstract

Compared to many common solid tumors, the main genetic drivers of most testicular germ cell tumors (TGCTs) are unknown. Decades of focus on genomic alterations in TGCTs including awareness of a near universal increase in copies of chromosome 12p have failed to uncover exceptional driver genes, especially in genes that can be targeted therapeutically. Thus far, TGCT patients have missed out on the benefits of targeted therapies available to treat most other malignancies. In the past decade there has been a greater appreciation that epigenetics may play an especially prominent role in TGCT etiology, progression, and hypersensitivity to conventional chemotherapy. While genetics undoubtedly plays a role in TGCT biology, this mini-review will focus on the epigenetic “states” or features of testicular cancer, with an emphasis on DNA methylation, histone modifications, and miRNAs associated with TGCT susceptibility, initiation, progression, and response to chemotherapy. In addition, we comment on the current status of epigenetic-based therapy and epigenetic biomarker development for TGCTs. Finally, we suggest a unifying “rock and a hard place” or “differentiate or die” model where the tumorigenicity and curability of TGCTs are both dependent on common but still ill-defined epigenetic states.

Case Report: The Complete Remission of a Mixed Germ Cell Tumor With Somatic Type Malignancy of Sarcoma Type With a GCT-Oriented Therapy: Clinical Findings and Genomic Profiling

Somatic malignant transformation in a germ cell tumor (GCT) is the development of non-germ malignancies; much of available literature refers to teratoma with malignant transformation (TMT). There are various transformation histologies such as sarcoma, adenocarcinoma, primitive neuroectodermal tumors, and more rarely carcinoid tumors, hemangioendothelioma, lymphoma, or nephroblastoma. The treatments of these entities include surgery and/or chemotherapy. A standard approach in choosing chemotherapy in TMT cases has not yet been established. Many authors suggest using chemotherapeutic agents based on the transformed histology, while others recommend GCT-oriented therapy combined with surgery as the primary treatment, reserving histology-driven chemotherapies for metastatic relapse. We report the clinical findings and the genomic profile of a mixed GCT case with somatic-type malignancy of sarcoma type. We achieved a complete radiological response with GCT-oriented chemotherapy performed as salvage therapy after sarcoma-histology therapy. In addition, molecular profiles with RNA-sequencing and exome sequencing analyses of the primary tumor and the tumor with somatic-type malignancy of sarcoma type were explored.

Germ cell tumors and associated hematologic malignancies evolve from a common shared precursor

Germ cell tumors (GCTs) are the most common cancer in men between the ages of 15 and 40. Although most patients are cured, those with disease arising in the mediastinum have distinctly poor outcomes. One in every 17 patients with primary mediastinal nonseminomatous GCTs develop an incurable hematologic malignancy and prior data intriguingly suggest a clonal relationship exists between hematologic malignancies and GCTs in these cases. To date, however, the precise clonal relationship between GCTs and the diverse additional somatic malignancies arising in such individuals have not been determined. Here, we traced the clonal evolution and characterized the genetic features of each neoplasm from a cohort of 15 patients with GCTs and associated hematologic malignancies. We discovered that GCTs and hematologic malignancies developing in such individuals evolved from a common shared precursor, nearly all of which harbored allelically imbalanced p53 and/or RAS pathway mutations. Hematologic malignancies arising in this setting genetically resembled mediastinal GCTs rather than de novo myeloid neoplasms. Our findings argue that this scenario represents a unique clinical syndrome, distinct from de novo GCTs or hematologic malignancies, initiated by an ancestral precursor that gives rise to the parallel evolution of GCTs and blood cancers in these patients.

Predicted 'wiring landscape' of Ras-effector interactions in 29 human tissues

Ras is a plasma membrane (PM)-associated signaling hub protein that interacts with its partners (effectors) in a mutually exclusive fashion. We have shown earlier that competition for binding and hence the occurrence of specific binding events at a hub protein can modulate the activation of downstream pathways. Here, using a mechanistic modeling approach that incorporates high-quality proteomic data of Ras and 56 effectors in 29 (healthy) human tissues, we quantified the amount of individual Ras-effector complexes, and characterized the (stationary) Ras "wiring landscape" specific to each tissue. We identified nine effectors that are in significant amount in complex with Ras in at least one of the 29 tissues. We simulated both mutant- and stimulus-induced network re-configurations, and assessed their divergence from the reference scenario, specifically discussing a case study for two stimuli in three epithelial tissues. These analyses pointed to 32 effectors that are in significant amount in complex with Ras only if they are additionally recruited to the PM, e.g. via membrane-binding domains or domains binding to activated receptors at the PM. Altogether, our data emphasize the importance of tissue context for binding events at the Ras signaling hub.

Developing and Using a Data Commons for Understanding the Molecular Characteristics of Germ Cell Tumors

Germ cell tumors (GCTs) are a rare disease, but they account for 15% of all malignancies diagnosed during adolescence. The biological mechanisms underpinning their development are only starting to be explored. Current GCT treatment may be associated with significant toxicity. Therefore, there is an urgent need to understand the molecular basis of GCT and identify biomarkers to tailor the therapy for individual patients. However, this research is severely hamstrung by the rarity of GCTs in individual hospitals/institutes. A publicly available genomic data commons with GCT datasets compiled from different institutes/studies would be a valuable resource to facilitate such research. In this study, we first reviewed publicly available web portals containing GCT genomics data, focusing on comparing data availability, data access, and analysis tools, and the limitations of using these resources for GCT molecular studies. Next, we specifically designed a GCT data commons with a web portal, GCT Explorer, to assist the research community to store, manage, search, share, and analyze data. The goal of this work is to facilitate GCT molecular basis exploration and translational research.

Assessing Homologous Recombination and Interstrand Cross-Link Repair in Embryonal Carcinoma Testicular Germ Cell Tumor Cell Lines

Testicular germ cell tumors (TGCTs) are typically exquisitely sensitive to DNA interstrand cross-link (ICLs) agents. ICLs covalently link both strands of the DNA duplex, impeding fundamental cellular processes like DNA replication to cause cell death. A leading drug used for the treatment of TGCTs is cisplatin, which introduces ICLs and leads to formation of double strand breaks (DSBs), a DNA lesion that can be repaired in the S/G2 phases of the cell cycle by homologous recombination (HR, also termed homology-direct repair). Although most TGCTs respond to cisplatin-induced ICLs, a fraction is resistant to treatment. One proposed mechanism of TGCT resistance to cisplatin is an enhanced ability to repair DSBs by HR. Other than HR, repair of the ICL-lesions requires additional DNA repair mechanisms, whose action might also be implemented in therapy-resistant cells. This chapter describes GFP assays to measure (a) HR proficiency following formation of a DSB by the endonuclease I-SceI, and (b) HR repair induced by site-specific ICL formation involving psoralen. These experimental approaches can be used to determine the proficiency of TGCT cell lines in DSB repair by HR in comparison to HR repair of ICLs, providing tools to better characterize their recombination profile. Protocols of these assays have been adapted for use in Embryonal Carcinoma (EC) TGCT cell lines. Assays only require transient introduction of plasmids within cells, affording the advantage of testing multiple cell lines in a relatively short time.

The rediscovery of platinum-based cancer therapy

Platinum (Pt) compounds entered the clinic as anticancer agents when cisplatin was approved in 1978. More than 40 years later, even in the era of precision medicine and immunotherapy, Pt drugs remain among the most widely used anticancer drugs. As Pt drugs mainly target DNA, it is not surprising that recent insights into alterations of DNA repair mechanisms provide a useful explanation for their success. Many cancers have defective DNA repair, a feature that also sheds new light on the mechanisms of secondary drug resistance, such as the restoration of DNA repair pathways. In addition, genome-wide functional screening approaches have revealed interesting insights into Pt drug uptake. About half of cisplatin and carboplatin but not oxaliplatin may enter cells through the widely expressed volume-regulated anion channel (VRAC). The analysis of this heteromeric channel in tumour biopsies may therefore be a useful biomarker to stratify patients for initial Pt treatments. Moreover, Pt-based approaches may be improved in the future by the optimization of combinations with immunotherapy, management of side effects and use of nanodelivery devices. Hence, Pt drugs may still be part of the standard of care for several cancers in the coming years.

Mediastinal germ cell tumors: many questions and perhaps an answer

Some germ cell tumors (GCTs) in men develop into hematologic malignancies; however, the clonal origins of such malignancies remain unknown. In this issue of the JCI, Taylor, Donoghue, et al. unravel the clonal relationship between primary mediastinal nonseminomas (PMNs) and hematologic somatic-type malignancies (HSTMs). Whole-exome sequencing was used to construct phylogenetic trees of the PMNs and the ensuing HSTM clones. HSTMs were derived from multiple distinct clones not detected within the PMNs. Clones from PMNs and HSTMs shared a common precursor, arguably an embryonal carcinoma cell resulting from a reprogrammed primordial germ cell from the thymus. Mutational and copy number variation analysis of a large cohort of patients with PMNs also demonstrated a high prevalence of TP53 mutations not found in testicular nonseminomas. These data likely explain why patients with PMNs are frequently resistant to platinum-based chemotherapy and provide TP53 mutations as potential targets.

Circ_0110805 Knockdown Enhances Cisplatin Sensitivity and Inhibits Gastric Cancer Progression by miR-299-3p/ENDOPDI Axis

Background

Gastric cancer is a prevalent primary stomach tumor. Cisplatin is frequently used to treat gastric cancer. However, the resistance of cisplatin in gastric cancer often occurs, which brings a heavy burden to gastric cancer treatment.

Methods

In this study, we revealed a novel underlying mechanism about cisplatin-resistant effect in gastric cancer. A Cell Counting Kit-8 (CCK-8) cell viability assay and a xenograft model were performed to evaluate the function of circRNA in the cisplatin resistance of gastric cancer.

Results

Compared with control groups, we observed that circ_0110805 was highly expressed, the mRNA and protein expression levels of ENDOPDI were dramatically upregulated, and the expression of miR-299-3p was significantly downregulated in gastric cancer cells, cisplatin-resistant gastric cancer tissues or cells. Functionally, circ_0110805 knockdown improved cisplatin sensitivity, induced cell apoptosis, whereas repressed cell viability, migration and invasion in AGS/DDP and HGC-27/DDP cells, which was reversed by miR-299-3p inhibitor. Additionally, ENDOPDI overexpression hindered the effects of miR-299-3p on cisplatin sensitivity and gastric cancer progression. Circ_0110805 knockdown enhanced cisplatin sensitivity in vivo. Mechanistically, circ_0110805 acted as a sponge of miR-299-3p and its targeted ENDOPDI.

Conclusion

We showed that circ_0110805 knockdown increased the sensitivity of gastric cancer to cisplatin, which also repressed gastric cancer progression by sponging miR-299-3p to downregulate ENDOPDI expression. It might provide a new insight for future studying cisplatin-resistant gastric cancer.

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.

Promising novel therapies for relapsed and refractory testicular germ cell tumors

INTRODUCTION

Germ cell tumors (GCTs) are the most common solid malignancies in young men. The overall cure rate of GCT patients in metastatic stage is excellent, however; patients with relapsed or refractory disease have poor prognosis. Attempts to treat refractory disease with novel effective treatment to improve prognosis have been historically dismal and the ability to predict prognosis and treatment response in GCTs did not sufficiently improve in the last three decades.

AREAS COVERED

We performed a comprehensive literature search of PubMed/MEDLINE to identify original and review articles (years 1964-2020) reporting on current improvement salvage treatment in GCTs and novel treatment options including molecularly targeted therapy and epigenetic approach. Review articles were further searched for additional original articles.

EXPERT OPINION

Despite multimodal treatment approaches the treatment of relapsed or platinum-refractory GCTs remains a challenge. High-dose chemotherapy (HDCT) regimens with autologous stem-cell transplant (ASCT) from peripheral blood showed promising results in larger retrospective studies. Promising results from in vitro studies raised high expectations in molecular targets. So far, the lacking efficacy in small and unselected trials do not shed a light on targeted therapy. Currently, wide inclusion of patients into clinical trials is highly advised.

Germ Cell Tumor Molecular Heterogeneity Revealed Through Analysis of Primary and Metastasis Pairs

PURPOSE

Although primary germ cell tumors (GCTs) have been extensively characterized, molecular analysis of metastatic sites has been limited. We performed whole-exome sequencing and targeted next-generation sequencing on paired primary and metastatic GCT samples in a patient cohort enriched for cisplatin-resistant disease.

PATIENTS AND METHODS

Tissue sequencing was performed on 100 tumor specimens from 50 patients with metastatic GCT, and sequencing of plasma cell-free DNA was performed for a subset of patients.

RESULTS

The mutational landscape of primary and metastatic pairs from GCT patients was highly discordant (68% of all somatic mutations were discordant). Whereas genome duplication was common and highly concordant between primary and metastatic samples, only 25% of primary-metastasis pairs had ≥ 50% concordance at the level of DNA copy number alterations (CNAs). Evolutionary-based analyses revealed that most mutations arose after CNAs at the respective loci in both primary and metastatic samples, with oncogenic mutations enriched in the set of early-occurring mutations versus variants of unknown significance (VUSs). TP53 pathway alterations were identified in nine cisplatin-resistant patients and had the highest degree of concordance in primary and metastatic specimens, consistent with their association with this treatment-resistant phenotype.

CONCLUSION

Analysis of paired primary and metastatic GCT specimens revealed significant molecular heterogeneity for both CNAs and somatic mutations. Among loci demonstrating serial genetic evolution, most somatic mutations arose after CNAs, but oncogenic mutations were enriched in the set of early-occurring mutations as compared with VUSs. Alterations in TP53 were clonal when present and shared among primary-metastasis pairs.

Genomic characteristics revealed by targeted exon sequencing of testicular germ cell tumors in Japanese men

OBJECTIVE

To investigate the somatic mutation profiles of testicular germ cell tumors in Japanese men.

METHODS

We analyzed the somatic missense mutation profile of testicular germ cell tumors among 21 Japanese men with seminoma (n = 14), pure embryonic carcinoma (n = 3) and mixed testicular germ cell tumor (n = 4) by targeted next-generation sequencing of 409 cancer-related genes covering 1.23 Mb of the genome.

RESULTS

We identified a total of 22 missense mutations in 21 primary testicular germ cell tumor samples (0.89 mutations/Mb), of which seven mutations were confirmed to be absent from the germline. KIT:p.Asn822Tyr, KIT:p.Leu576Pro, PIK3CA:p.Glu542Lys and FBXW7:p.Arg505His were statistically and functionally potential. A total of 18 missense mutations were previously unknown in testicular germ cell tumors. PDGFRA amplification from one patient with seminoma was detected. KIT, BCR,PIK3CG, PIK3CA and PDGFRA mutations involved in aberrant signaling of the KIT-PI3K-AKT pathway was detected in 27.3% of detected mutations.

CONCLUSIONS

The present investigation identified a low mutation rate in testicular germ cell tumors among Asian patients, 18 novel mutations and PDGFRA amplification. Limitations of the present study are the small sample and missing normal DNA for some testicular germ cell tumors.

Comprehensive genetic analysis of pediatric germ cell tumors identifies potential drug targets

To elucidate the molecular pathogenesis of pediatric germ cell tumors (GCTs), we performed DNA methylation array analysis, whole transcriptome sequencing, targeted capture sequencing, and single-nucleotide polymorphism array analysis using 51 GCT samples (25 female, 26 male), including 6 germinomas, 2 embryonal carcinomas, 4 immature teratomas, 3 mature teratomas, 30 yolk sac tumors, and 6 mixed germ cell tumors. Among the 51 samples, 11 were from infants, 23 were from young children, and 17 were from those aged ≥10 years. Sixteen of the 51 samples developed in the extragonadal regions. Germinomas showed upregulation of pluripotent genes and global hypomethylation. Pluripotent genes were also highly expressed in embryonal carcinomas. These genes may play essential roles in embryonal carcinomas given that their binding sites are hypomethylated. Yolk sac tumors exhibited overexpression of endodermal genes, such as GATA6 and FOXA2, the binding sites of which were hypomethylated. Interestingly, infant yolk sac tumors had different DNA methylation patterns from those observed in older children. Teratomas had higher expression of ectodermal genes, suggesting a tridermal nature. Based on our results, we suggest that KIT, TNFRSF8, and ERBB4 may be suitable targets for the treatment of germinoma, embryonal carcinomas, and yolk sac tumors, respectively.

Yasuo Kubota et al. report a multi-omic analysis of pediatric germ cell tumors from 51 patients ranging in age from 2 months to 19 years. They identify unique methylation, expression, and mutational patterns for each of the main subtypes and propose potential target genes for treatments against the three main subtypes.

Amino Acids Regulate Cisplatin Insensitivity in Neuroblastoma

Simple Summary

Neuroblastomas mostly show poor response to the Cisplatin therapy. Amino acids serve as building blocks for proteins, which are acquired either through diet or protein breakdown. Our study reveals high amino acid pools and dependence of Cisplatin-tolerant neuroblastomas cells on amino acids for their survival, especially, in drug treated conditions. Our study also demonstrates that response of neuroblastomas to Cisplatin can be improved by decreasing cellular amino acid levels either by reducing amino acid supplements or by applying autophagy inhibitor, Hydroxychloroquine. Thus, our findings establish that neuroblastomas can be sensitized to Cisplatin by targeting amino acid metabolism.

Abstract

Neuroblastoma are pediatric, extracranial malignancies showing alarming survival prognosis outcomes due to their resilience to current aggressive treatment regimens, including chemotherapies with cisplatin (CDDP) provided in the first line of therapy regimens. Metabolic deregulation supports tumor cell survival in drug-treated conditions. However, metabolic pathways underlying cisplatin-resistance are least studied in neuroblastoma. Our metabolomics analysis revealed that cisplatin-insensitive cells alter their metabolism; especially, the metabolism of amino acids was upregulated in cisplatin-insensitive cells compared to the cisplatin-sensitive neuroblastoma cell line. A significant increase in amino acid levels in cisplatin-insensitive cells led us to hypothesize that the mechanisms upregulating intracellular amino acid pools facilitate insensitivity in neuroblastoma. We hereby report that amino acid depletion reduces cell survival and cisplatin-insensitivity in neuroblastoma cells. Since cells regulate their amino acids levels through processes, such as autophagy, we evaluated the effects of hydroxychloroquine (HCQ), a terminal autophagy inhibitor, on the survival and amino acid metabolism of cisplatin-insensitive neuroblastoma cells. Our results demonstrate that combining HCQ with CDDP abrogated the amino acid metabolism in cisplatin-insensitive cells and sensitized neuroblastoma cells to sub-lethal doses of cisplatin. Our results suggest that targeting of amino acid replenishing mechanisms could be considered as a potential approach in developing combination therapies for treating neuroblastomas.

Thoracic Metastasectomy in Germ Cell Tumor Patients Treated With First-line Versus Salvage Therapy

BACKGROUND

Outcomes after thoracic metastasectomy in patients with testicular germ cell tumors (GCTs) who received first-line chemotherapy alone versus salvage chemotherapy remain unexplored.

METHODS

We conducted a retrospective review of patients who underwent thoracic metastasectomy for residual GCT between 1997 and 2019 at a single tertiary center. Factors associated with progression-free survival (PFS) and overall survival (OS) were assessed using multivariable Cox regression.

RESULTS

Of 251 patients, 191 received only first-line chemotherapy (76%) and 60 received salvage chemotherapy (24%). Median follow-up was 3.45 years (interquartile range, 1-7.93 years). Among first-line patients without teratoma in the primary tumor, with necrosis in the retroperitoneal nodes and normalized or decreasing serum tumor markers, 17 of 20 had intrathoracic necrosis (85%). Among first-line and salvage patients, respectively, 5-year OS was 93% (95% confidence interval [CI], 89%-98%) versus 63% (95% CI, 51%-78%; P < .001), and 5-year PFS was 69% (95% CI, 62%-77%) versus 40% (95% CI, 29%-56%; P < .001). On multivariable analysis, multiple lung lesions (hazard ratio [HR] = 3.01; 95% CI, 1.50-6.05; P = .002) and brain metastasis (HR = 4.51; 95% CI, 2.34-8.73; P < .001) at diagnosis, salvage chemotherapy (HR = 1.85; 95% CI, 1.10-3.13; P = .021), teratoma (HR = 2.68; 95% CI, 1.50-4.78; P = .001), and viable malignancy (HR = 4.34; 95% CI, 2.44-7.71; P < .001) were associated with worse PFS.

CONCLUSIONS

Although GCT patients treated with salvage chemotherapy followed by thoracic metastasectomy have more aggressive disease and poorer PFS, they can achieve encouraging OS. Our findings highlight the integral role of aggressive thoracic metastasectomy in the treatment of GCT patients with residual thoracic disease after first line-only or salvage chemotherapy.

Report From the International Society of Urological Pathology (ISUP) Consultation Conference on Molecular Pathology of Urogenital Cancers: IV: Current and Future Utilization of Molecular-Genetic Tests for Testicular Germ Cell Tumors

The International Society of Urological Pathology (ISUP) organized a Consultation Conference in March 2019 dealing with applications of molecular pathology in Urogenital Pathology, including testicular tumors (with a focus on germ cell tumors [GCTs]), preceded by a survey among its members to get insight into current practices in testicular germ cell tumor (TGCT) diagnostics and adoption of the ISUP immunohistochemical guidelines published in 2014. On the basis of the premeeting survey, the most commonly used immunomarker panel includes OCT3/4, placental alkaline phosphate, D2-40, SALL4, CD117, and CD30 for GCTs and the documentation of germ cell neoplasia in situ (GCNIS). Molecular testing, specifically 12p copy gain, is informative to distinguish non-GCNIS versus GCNIS related GCTs, and establishing germ cell origin of tumors both in the context of primary and metastatic lesions. Other molecular methodologies currently available but not widely utilized for TGCTs include genome-wide and targeted approaches for specific genetic anomalies, P53 mutations, genomic MDM2 amplification, and detection of the p53 inactivating miR-371a-3p. The latter also holds promise as a serum marker for malignant TGCTs. This manuscript provides an update on the classification of TGCTs, and describes the current and future role of molecular-genetic testing. The following recommendations are made: (1) Presence of GCNIS should be documented in all cases along with extent of spermatogenesis; (2) Immunohistochemical staining is optional in the following scenarios: identification of GCNIS, distinguishing embryonal carcinoma from seminoma, confirming presence of yolk sac tumor and/or choriocarcinoma, and differentiating spermatocytic tumor from potential mimics; (3) Detection of gain of the short arm of chromosome 12 is diagnostic to differentiate between non-GCNIS versus GCNIS related GCTs and supportive to the germ cell origin of both primary and metastatic tumors.

Cisplatin Resistance in Testicular Germ Cell Tumors: Current Challenges from Various Perspectives

Testicular germ cell tumors share a marked sensitivity to cisplatin, contributing to their overall good prognosis. However, a subset of patients develop resistance to platinum-based treatments, by still-elusive mechanisms, experiencing poor quality of life due to multiple (often ineffective) interventions and, eventually, dying from disease. Currently, there is a lack of defined treatment opportunities for these patients that tackle the mechanism(s) underlying the emergence of resistance. Herein, we aim to provide a multifaceted overview of cisplatin resistance in testicular germ cell tumors, from the clinical perspective, to the pathobiology (including mechanisms contributing to induction of the resistant phenotype), to experimental models available for studying this occurrence. We provide a systematic summary of pre-target, on-target, post-target, and off-target mechanisms putatively involved in cisplatin resistance, providing data from preclinical studies and from those attempting validation in clinical samples, including those exploring specific alterations as therapeutic targets, some of them included in ongoing clinical trials. We briefly discuss the specificities of resistance related to teratoma (differentiated) phenotype, including the phenomena of growing teratoma syndrome and development of somatic-type malignancy. Cisplatin resistance is most likely multifactorial, and a combination of therapeutic strategies will most likely produce the best clinical benefit.

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.

Development of a Data Model and Data Commons for Germ Cell Tumors

Germ cell tumors (GCTs) are considered a rare disease but are the most common solid tumors in adolescents and young adults, accounting for 15% of all malignancies in this age group. The rarity of GCTs in some groups, particularly children, has impeded progress in treatment and biologic understanding. The most effective GCT research will result from the interrogation of data sets from historical and prospective trials across institutions. However, inconsistent use of terminology among groups, different sample-labeling rules, and lack of data standards have hampered researchers' efforts in data sharing and across-study validation. To overcome the low interoperability of data and facilitate future clinical trials, we worked with the Malignant Germ Cell International Consortium (MaGIC) and developed a GCT clinical data model as a uniform standard to curate and harmonize GCT data sets. This data model will also be the standard for prospective data collection in future trials. Using the GCT data model, we developed a GCT data commons with data sets from both MaGIC and public domains as an integrated research platform. The commons supports functions, such as data query, management, sharing, visualization, and analysis of the harmonized data, as well as patient cohort discovery. This GCT data commons will facilitate future collaborative research to advance the biologic understanding and treatment of GCTs. Moreover, the framework of the GCT data model and data commons will provide insights for other rare disease research communities into developing similar collaborative research platforms.

p53 and MDM2 expression in primary and metastatic testicular germ cell tumors: Association with clinical outcome

BACKGROUND

Testicular germ cell tumors (TGCTs) are highly sensitive to platinum-based chemotherapy, and wild-type p53 seems to play a pivotal role in this susceptibility. On the other hand, overexpression of MDM2 seems to entail treatment resistance and unfavorable prognosis.

OBJECTIVES

We aimed to describe p53 and MDM2 immunoexpression in a well-characterized cohort of primary and metastatic TGCTs and evaluate associations with clinicopathological and prognostic variables, including survival.

MATERIALS AND METHODS

237 primary tumor samples and 12 metastases were evaluated for p53 and MDM2 immunoexpression using digital image analysis. Clinical records of all patients were reviewed for baseline clinical/pathologic characteristics and follow-up.

RESULTS

A significant positive correlation between p53 and MDM2 H-scores was found (r_s  = 0.590, P < .0001). Non-seminomas showed significantly higher expression levels of both p53 and MDM2 (P = .0002, P < .0001), which peaked in embryonal carcinomas and choriocarcinomas. Percentage of immunoexpressing cells and H-score were significantly higher in chemo-treated metastases compared with chemo-naïve primary tumors for MDM2 (P ≤ .0001 for both), but not for p53 (P = .919 and P = .703, respectively). Cases with higher MDM2 immunoexpression showed a statistically significant trend for association with poorer prognosis (P = .043). Relapse/progression-free survival at 12 months post-diagnosis was lower in the "MDM2-high" (≥P50) vs. the "MDM2-low" (<P50) expression groups.

DISCUSSION AND CONCLUSION

In TGCTs, MDM2 overexpression may indicate a more aggressive tumor phenotype, with propensity for therapy resistance and recurrence. If validated in larger multi-institutional studies with precise quantification, it may be envisioned as a useful predictive biomarker of poor response to cisplatin.

Latest progress in molecular biology and treatment in genitourinary tumours

The management of genitourinary cancer, including bladder, prostate, renal and testicular cancer, has evolved dramatically in recent years due to a better understanding of tumour genetic mutations, alterations in molecular pathways, and to the development of new kinds of drugs such as targeted therapies and immunotherapies. In the field of immunotherapy, new drugs focused on stimulating, enhancing and modulating the immune system to detect and destroy cancer, have been recently discovered. Research in oncology moves quickly and new data of great relevance for clinical practice are communicated every year. For this reason, a group of experts, focused exclusively on the treatment of genitourinary tumours and who get together every year in the BestGU conference to assess the latest progress in this field have summarized the most important advances in a single review, along with a critical assessment of whether these results should alter daily clinical practice.

CDK4/6 inhibition presents as a therapeutic option for paediatric and adult germ cell tumours and induces cell cycle arrest and apoptosis via canonical and non-canonical mechanisms

BACKGROUND

Germ cell tumours (GCTs) are the most common solid malignancies in young men. Although high cure rates can be achieved, metastases, resistance to cisplatin-based therapy and late toxicities still represent a lethal threat, arguing for the need of new therapeutic options. In this study, we analysed the potential of cyclin-dependent kinase 4/6 (CDK4/6) inhibitors palbociclib and ribociclib (PaRi) as molecular drugs to treat cisplatin-resistant and -sensitive paediatric and adult GCTs.

METHODS

Ten GCT cell lines, including cisplatin-resistant subclones and non-malignant controls, were treated with PaRi and screened for changes in viability (triphenyl tetrazolium chloride (XTT) assay), apoptosis rates (flow cytometry, caspase assay), the cell cycle (flow cytometry), the transcriptome (RNA-sequencing, quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR) and on protein level (western blot). Expression profiling was performed on paediatric and adult GCT tissues (expression microarrays, qRT-PCR, immunohistochemistry, 'The Cancer Genome Atlas' database).

RESULTS

We demonstrate that adult GCTs highly express CDK4, while paediatric GCTs strongly express CDK6 instead. Thus, both GCT types are potentially treatable by PaRi. GCTs presented as highly sensitive towards PaRi, which caused a decrease in viability, cell cycle arrest and apoptosis. Although GCTs mainly arrested in the G1/G0 phase, some embryonal carcinoma cell lines were able to bypass the G1/S checkpoint and progressed to the G2/M phase. We found that upregulation of CDK3 and downregulation of many mitosis regulation factors, like the HAUS genes, might be responsible for bypassing the G1/S checkpoint and termination of mitosis, respectively. We postulate that GCT cells do not tolerate these alterations in the cell cycle and eventually induce apoptosis.

CONCLUSION

Our study highlights PaRi as therapeutic options for cisplatin-resistant and -sensitive paediatric and adult GCTs.

Dysregulation of Rho GTPases in Human Cancers

Rho GTPases play central roles in numerous cellular processes, including cell motility, cell polarity, and cell cycle progression, by regulating actin cytoskeletal dynamics and cell adhesion. Dysregulation of Rho GTPase signaling is observed in a broad range of human cancers, and is associated with cancer development and malignant phenotypes, including metastasis and chemoresistance. Rho GTPase activity is precisely controlled by guanine nucleotide exchange factors, GTPase-activating proteins, and guanine nucleotide dissociation inhibitors. Recent evidence demonstrates that it is also regulated by post-translational modifications, such as phosphorylation, ubiquitination, and sumoylation. Here, we review the current knowledge on the role of Rho GTPases, and the precise mechanisms controlling their activity in the regulation of cancer progression. In addition, we discuss targeting strategies for the development of new drugs to improve cancer therapy.

Genomic landscape of platinum resistant and sensitive testicular cancers

While most testicular germ cell tumours (TGCTs) exhibit exquisite sensitivity to platinum chemotherapy, ~10% are platinum resistant. To gain insight into the underlying mechanisms, we undertake whole exome sequencing and copy number analysis in 40 tumours from 26 cases with platinum-resistant TGCT, and combine this with published genomic data on an additional 624 TGCTs. We integrate analyses for driver mutations, mutational burden, global, arm-level and focal copy number (CN) events, and SNV and CN signatures. Albeit preliminary and observational in nature, these analyses provide support for a possible mechanistic link between early driver mutations in RAS and KIT and the widespread copy number events by which TGCT is characterised.

RAC1 as a Therapeutic Target in Malignant Melanoma

Small GTPases of the RAS and RHO families are related signaling proteins that, when activated by growth factors or by mutation, drive oncogenic processes. While activating mutations in KRAS, NRAS, and HRAS genes have long been recognized and occur in many types of cancer, similar mutations in RHO family genes, such as RAC1 and RHOA, have only recently been detected as the result of extensive cancer genome-sequencing efforts and are linked to a restricted set of malignancies. In this review, we focus on the role of RAC1 signaling in malignant melanoma, emphasizing recent advances that describe how this oncoprotein alters melanocyte proliferation and motility and how these findings might lead to new therapeutics in RAC1-mutant tumors.

Genetics of testicular germ cell tumors

PURPOSE OF REVIEW

Understanding the molecular basis underlying testicular germ cell tumors (TGCTs) may help improve patient outcomes, particularly for patients with poorer risk or chemoresistant disease. Here, we review the major contemporary advances in elucidating TGCT genetics by discussing patterns of TGCT inheritance, recent genomic and transcriptomic discoveries in TGCT, and the role of genetics in predicting therapeutic resistance and in guiding treatment.

RECENT FINDINGS

In the absence of a major high-penetrance TGCT susceptibility gene, inheritance is likely driven by a complex polygenic model with considerable variation. The most common genomic alterations found in TGCTs include gains in chromosome 12p and mutations in KIT, KRAS, and NRAS, particularly in seminomas. Sensitivity to cisplatin-based chemotherapy likely relies on intact TP53, reciprocal loss of heterozygosity, and high mitochondrial priming. Targetable mutations are uncommon in TGCTs, however, posing a challenge for the development of effective personalized therapies. Consistent with the characteristically low tumor mutational burden, immune checkpoint inhibitors do not appear to be effective for most TGCTs.

SUMMARY

Refinements in next-generation sequencing techniques over the last few years have enabled considerable advances in elucidating the genomic, transcriptomic, and epigenetic landscape of TGCTs. Future efforts focused on developing novel treatment modalities are needed.

Pharmacogenomics for the efficacy of platinum-based chemotherapy: Old drugs, new integrated perspective

Platinum-based chemotherapy remains the cornerstone of treatment for many malignancies. However, although therapeutic efficiency varies greatly among individuals, there is a lack of pharmacogenomic biomarkers that can be used in clinical settings to identify chemosensitive patients and allow stratification. With the development of high-throughput screening techniques and systems biology approaches, a growing body of evidence has shown that platinum resistance is a multifactorial, multi-dimensional, dynamic process incorporating genetic background, tumor evolution and gut microbes. This review critically summarizes potential pharmacogenomic biomarkers for predicting the efficacy of platinum drugs and provides a comprehensive, time-varying perspective that integrates multiple markers.

A novel circular RNA circFN1 enhances cisplatin resistance in gastric cancer via sponging miR-182-5p

Cisplatin (CDDP) is commonly used for gastric cancer (GC) chemotherapy. However, after several CDDP-based treatment cycles, patients always acquire chemotherapy resistance, which limits the overall clinical efficacy of the treatment. Clarification of the mechanisms responsible for CDDP resistance is required to improve therapeutic outcomes for patients. Circular RNAs (circRNAs) are noncoding RNAs involved in the pathogenesis of cancer, although their role in the mechanism underlying CDDP resistance in GC remains unknown. In the present study, we explored the underlying roles of circRNAs in the modulation of CDDP resistance in CDDP-sensitive and CDDP-resistant human GC cells. Using RNA sequencing and quantitative reverse transcription polymerase chain reaction, expression of circFN1 (originating from exons 10, 11, and 12 of the FN1 gene hsa_circ_0058147) was higher in CDDP-resistant GC cells and tissues. CircFN1 upregulation in GC patients treated by CDDP was significantly correlated with aggressive biological behavior. CircFN1 promoted viability and inhibited apoptosis of GC cells exposed to CDDP in vivo and in vitro. Furthermore, circFN1 suppressed GC cell apoptosis by "sponging" miR-182-5p. These findings demonstrate the involvement of circFN1 in CDDP resistance of GC and implicate circFN1 as a therapeutic target for GC patients treated with CDDP. It provides novel evidence of the function of circRNAs as microRNA sponges and highlight a potential therapeutic target for extinguishing CDDP resistance in patients with GC.

ESMO Consensus Conference on testicular germ cell cancer: diagnosis, treatment and follow-up

The European Society for Medical Oncology (ESMO) consensus conference on testicular cancer was held on 3-5 November 2016 in Paris, France. The conference included a multidisciplinary panel of 36 leading experts in the diagnosis and treatment of testicular cancer (34 panel members attended the conference; an additional two panel members [CB and K-PD] participated in all preparatory work and subsequent manuscript development). The aim of the conference was to develop detailed recommendations on topics relating to testicular cancer that are not covered in detail in the current ESMO Clinical Practice Guidelines (CPGs) and where the available level of evidence is insufficient. The main topics identified for discussion related to: (1) diagnostic work-up and patient assessment; (2) stage I disease; (3) stage II-III disease; (4) post-chemotherapy surgery, salvage chemotherapy, salvage and desperation surgery and special topics; and (5) survivorship and follow-up schemes. The experts addressed questions relating to one of the five topics within five working groups. Relevant scientific literature was reviewed in advance. Recommendations were developed by the working groups and then presented to the entire panel. A consensus vote was obtained following whole-panel discussions, and the consensus recommendations were then further developed in post-meeting discussions in written form. This manuscript presents the results of the expert panel discussions, including the consensus recommendations and a summary of evidence supporting each recommendation. All participants approved the final manuscript.

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.

Predicting Gonadal Germ Cell Cancer in People with Disorders of Sex Development; Insights from Developmental Biology

The risk of gonadal germ cell cancer (GGCC) is increased in selective subgroups, amongst others, defined patients with disorders of sex development (DSD). The increased risk is due to the presence of part of the Y chromosome, i.e., GonadoBlastoma on Y chromosome GBY region, as well as anatomical localization and degree of testicularization and maturation of the gonad. The latter specifically relates to the germ cells present being at risk when blocked in an embryonic stage of development. GGCC originates from either germ cell neoplasia in situ (testicular environment) or gonadoblastoma (ovarian-like environment). These precursors are characterized by presence of the markers OCT3/4 (POU5F1), SOX17, NANOG, as well as TSPY, and cKIT and its ligand KITLG. One of the aims is to stratify individuals with an increased risk based on other parameters than histological investigation of a gonadal biopsy. These might include evaluation of defined susceptibility alleles, as identified by Genome Wide Association Studies, and detailed evaluation of the molecular mechanism underlying the DSD in the individual patient, combined with DNA, mRNA, and microRNA profiling of liquid biopsies. This review will discuss the current opportunities as well as limitations of available knowledge in the context of predicting the risk of GGCC in individual patients.

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.

Clinical Benefit of Sorafenib Combined with Paclitaxel and Carboplatin to a Patient with Metastatic Chemotherapy-Refractory Testicular Tumors

Testicular cancer is one of the few tumor types that have not yet benefited from targeted therapy. Still no new active agents for treating this cancer have been identified over the past 15 years. Once patients are refractory to cisplatin-based chemotherapy, they will be expected to die from testicular cancer. This report describes a 21-year-old man who was refractory to chemotherapy and immunotherapy. Whole exome sequencing and low-depth whole genome sequencing confirmed the KRAS gene amplification, which may lead to the tumor cells' progression and proliferation. After discussion at the molecular tumor board, the patient was offered paclitaxel, carboplatin, and sorafenib (CPS) based on a phase III clinical trial of melanoma with KRAS gene copy gains. After treatment with CPS, the patient achieved excellent curative effects. Because of a nearly 50% frequency of KRAS amplification in chemotherapy-refractory testicular germ cells, CPS regimen may provide a new therapy, but it still warrants further validation in clinical studies. KEY POINTS: Chemotherapy-refractory testicular cancer has a very poor prognosis resulting in a lack of effective targeted therapies. KRAS gene amplification occurs in nearly 20% of testicular cancer and 50% of chemotherapy-refractory testicular cancer. KRAS amplification may activate the MAPK signaling pathway, and inhibition of MAPK by sorafenib combined with paclitaxel and carboplatin could be a viable option based on a phase III clinical trial of melanoma.To the authors' knowledge, this is the first report of response to sorafenib-based combination targeted therapy in a patient with chemotherapy-refractory testicular cancer.Clinical genomic profiling can confirm copy number variation of testicular cancer and provide insights on therapeutic options.

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.

Human germ cell tumours from a developmental perspective

Human germ cell tumours (GCTs) are derived from stem cells of the early embryo and the germ line. They occur in the gonads (ovaries and testes) and also in extragonadal sites, where migrating primordial germ cells are located during embryogenesis. This group of heterogeneous neoplasms is unique in that their developmental potential is in effect determined by the latent potency state of their cells of origin, which are reprogrammed to omnipotent, totipotent or pluripotent stem cells. Seven GCT types, defined according to their developmental potential, have been identified, each with distinct epidemiological and (epi)genomic features. Heritable predisposition factors affecting the cells of origin and their niches likely explain bilateral, multiple and familial occurrences of the different types of GCTs. Unlike most other tumour types, GCTs are rarely caused by somatic driver mutations, but arise through failure to control the latent developmental potential of their cells of origin, resulting in their reprogramming. Consistent with their non-mutational origin, even the malignant tumours of the group are characterized by wild-type TP53 and high sensitivity for DNA damage. However, tumour progression and the rare occurrence of treatment resistance are driven by embryonic epigenetic state, specific (sub)chromosomal imbalances and somatic mutations. Thus, recent progress in understanding GCT biology supports a comprehensive developmental pathogenetic model for the origin of all GCTs, and provides new biomarkers, as well as potential targets for treatment of resistant disease.

Rho GTPases in cancer: friend or foe?

The Rho GTPases RhoA, Rac1, and Cdc42 are important regulators of cytoskeletal dynamics. Although many in vitro and in vivo data indicate tumor-promoting effects of activated Rho GTPases, also tumor suppressive functions have been described, suggesting either highly cell-type-specific functions for Rho GTPases in cancer or insufficient cancer models. The availability of a large number of cancer genome-sequencing data by The Cancer Genome Atlas (TCGA) allows for the investigation of Rho GTPase function in human cancers in silico. This information should be used to improve our in vitro and in vivo cancer models, which are essential for a molecular understanding of Rho GTPase function in malignant tumors and for the potential development of cancer drugs targeting Rho GTPase signaling.