Phase II study of everolimus in refractory testicular germ cell tumors

Seminoma and dysgerminoma: evidence for alignment of clinical trials and de-escalation of systemic chemotherapy

Malignant germ cell tumours are a group of rare cancers whose incidence peaks in late adolescence and early adulthood. Dysgerminomas of the ovary and seminomas of the testis are analogous diseases, but seminomas have a 10-fold higher incidence. The two tumours are morphologically identical and are only differentiated by surrounding organ-specific tissue or testicular germ cell neoplasia in situ. They share genetic features including KIT and RAS mutations, amplification of chromosome 12p, and expression of pluripotency markers (NANOG (Nanog homeobox), OCT3/4 (Octamer-binding transcription factor 3/4), and SAL4 (Spalt-like trascription factor 4)). Both histologies are exquisitely sensitive to platinum chemotherapy, and the combination of bleomycin, etoposide, and cisplatin (BEP) yields survival rates greater than 90%. However, BEP causes significant, lifelong toxicity (cardiovascular, renal, respiratory, and neurological) in these young patients with an expectation of cure. Here, we comprehensively review the biological features of dysgerminoma and seminoma to demonstrate that they are biologically analogous diseases. We present available clinical trial data supporting de-escalation of chemotherapy treatment. Finally, we propose that future trials should enrol men, women, and children to benefit all patients regardless of age or sex.

Clinical Challenges in the Management of Malignant Ovarian Germ Cell Tumours

Nonepithelial ovarian cancers (NEOC) are a group of rare malignancies, including germ cell tumours (GCT) and sex cord-stromal tumours (SCST), along with small-cell carcinomas and sarcomas. GCTs represent 2-5% of ovarian cancers, with a yearly incidence of 4:100,000, and they usually affect young women and adolescents. Precursory germ cells of the ovary form the basis of GCT. They are histologically classified into primitive GCT, teratomas, and monodermal and somatic-type tumours associated with dermoid cysts. A primitive GCT can be either a yolk sac tumour (YST), dysgerminoma, or mixed germ cell neoplasm. Teratomas are either mature (benign) or immature (malignant). Given that malignant GCTs occur rarely compared to epithelial ovarian tumours (EOC), greater focus is required in their diagnosis and treatment. In this article, we review the epidemiology, clinical manifestations, diagnosis, and molecular biology, along with the management and therapeutic challenges.

Loss of liver kinase B1 in human seminoma

Testicular cancer is a common malignancy of young males and is believed to be originated from defective embryonic or adult germ cells. Liver kinase B1 (LKB1) is a serine/threonine kinase and a tumor suppressor gene. LKB1 is a negative regulator of the mammalian target of rapamycin (mTOR) pathway, often inactivated in many human cancer types. In this study, we investigated the involvement of LKB1 in the pathogenesis of testicular germ cell cancer. We performed immunodetection of LKB1 protein in human seminoma samples. A 3D culture model of human seminoma was developed from TCam-2 cells, and two mTOR inhibitors were tested for their efficacy against these cancer cells. Western blot and mTOR protein arrays were used to show that these inhibitors specifically target the mTOR pathway. Examination of LKB1 showed reduced expression in germ cell neoplasia in situ lesions and seminoma compared to adjacent normal-appearing seminiferous tubules where the expression of this protein was present in the majority of germ cell types. We developed a 3D culture model of seminoma using TCam-2 cells, which also showed reduced levels of LKB1 protein. Treatment of TCam-2 cells in 3D with two well-known mTOR inhibitors resulted in reduced proliferation and survival of TCam-2 cells. Overall, our results support that downregulation or loss of LKB1 marks the early stages of the pathogenesis of seminoma, and the suppression of downstream signaling to LKB1 might be an effective therapeutic strategy against this cancer type.

Immune checkpoint inhibitor using in cases with gestational trophoblastic diseases

Gestational trophoblastic neoplasias (GTNs) are chemosensitive disorders with very high cure rates. However, individuals with chemoresistant diseases pass away as a result of their illness, necessitating the use of innovative medications. Immune checkpoint inhibitors (ICIs) are a critical component of the strategy for the management of drug-resistant GTD due to the high rate of PD-1 expression and the paternal genetic inheritance in GTNs. Immunotherapy is mentioned as a potential therapeutic approach for chemotherapy-resistant GTD in the most recent worldwide recommendations. However, multicenter worldwide collaborative studies are required to give additional evidence to detect and identify prognostic markers due to the rarity of GTDs and the dearth of data in the literature.

Phase II study of Disulfiram and Cisplatin in Refractory Germ Cell Tumors. The GCT-SK-006 phase II trial

BACKGROUND

Multiple relapsed/refractory germ cell tumor (GCT) patients have extremely poor prognosis. Cisplatin resistant testicular GCTs overexpress aldehyde-dehydrogenase (ALDH) isoforms and inhibition of ALDH activity by disulfiram is associated with reconstitution of cisplatin sensitivity in vitro as well as in animal model. This study aimed to determine the efficacy and toxicity of ALDH inhibitor disulfiram in combination with cisplatin in patients with multiple relapsed/refractory GCTs.

METHODS

Disulfiram was administered at a dose of 400 mg daily until progression or unacceptable toxicity, cisplatin was administered at dose 50 mg/m² day 1 and 2, every 3 weeks. Twelve evaluable patients had to be enrolled into the first cohort, and if 0 of 12 patients had treatment response, the study was to be terminated. The results of the first stage of the trial are presented in this report.

RESULTS

Twelve patients with multiple relapsed/refractory GCTs were enrolled in the phase II study from May 2019 to September 2021. Median number of treatment cycles was 2 (range 1-6). None of patients achieved objective response to treatment, therefore the study was terminated in first stage. Median progression-free survival was 1.4 months, 95% CI (0.7-1.5 months), and median overall survival was 2.9 months 95% CI (1.5-4.7 months). Disease stabilization for at least 3 months was observed in 2 (16.7%) patients. Treatment was well tolerated, however, 5 (41.7%) of patients experienced grade 3/4 fatigue, 4 (33.3%) thrombocytopenia, 3 (25.0%) anemia, while 2 (16.7%) experienced neutropenia, nausea and infection.

CONCLUSIONS

This study failed to achieve its primary endpoint and our data suggest limited efficacy of disulfiram in restoring sensitivity to cisplatin in multiple relapsed/refractory GCTs.

Overcoming Chemotherapy Resistance in Germ Cell Tumors

Testicular germ cell tumors (GCTs) are highly curable malignancies. Excellent survival rates in patients with metastatic disease can be attributed to the exceptional sensitivity of GCTs to cisplatin-based chemotherapy. This hypersensitivity is probably related to alterations in the DNA repair of cisplatin-induced DNA damage, and an excessive apoptotic response. However, chemotherapy fails due to the development of cisplatin resistance in a proportion of patients. The molecular basis of this resistance appears to be multifactorial. Tracking the mechanisms of cisplatin resistance in GCTs, multiple molecules have been identified as potential therapeutic targets. A variety of therapeutic agents have been evaluated in preclinical and clinical studies. These include different chemotherapeutics, targeted therapies, such as tyrosine kinase inhibitors, mTOR inhibitors, PARP inhibitors, CDK inhibitors, and anti-CD30 therapy, as well as immune-checkpoint inhibitors, epigenetic therapy, and others. These therapeutics have been used as single agents or in combination with cisplatin. Some of them have shown promising in vitro activity in overcoming cisplatin resistance, but have not been effective in clinical trials in refractory GCT patients. This review provides a summary of current knowledge about the molecular mechanisms of cisplatin sensitivity and resistance in GCTs and outlines possible therapeutic approaches that seek to overcome this chemoresistance.

A stochastically curtailed single‐arm phase II trial design for binary outcomes

Phase II clinical trials are a critical aspect of the drug development process. With drug development costs ever increasing, novel designs that can improve the efficiency of phase II trials are extremely valuable.Phase II clinical trials for cancer treatments often measure a binary outcome. The final trial decision is generally to continue or cease development. When this decision is based solely on the result of a hypothesis test, the result may be known with certainty before the planned end of the trial. Unfortunately, there is often no opportunity for early stopping when this occurs.Some existing designs do permit early stopping in this case, accordingly reducing the required sample size and potentially speeding up drug development. However, more improvements can be achieved by stopping early when the final trial decision is very likely, rather than certain, known as stochastic curtailment. While some authors have proposed approaches of this form, these approaches have various limitations.In this work we address these limitations by proposing new design approaches for single-arm phase II binary outcome trials that use stochastic curtailment. We use exact distributions, avoid simulation, consider a wider range of possible designs and permit early stopping for promising treatments. As a result, we are able to obtain trial designs that have considerably reduced sample sizes on average.

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.

Programmed cell death, redox imbalance, and cancer therapeutics

Cancer cells are disordered by nature and thus featured by higher internal redox level than healthy cells. Redox imbalance could trigger programmed cell death if exceeded a certain threshold, rendering therapeutic strategies relying on redox control a possible cancer management solution. Yet, various programmed cell death events have been consecutively discovered, complicating our understandings on their associations with redox imbalance and clinical implications especially therapeutic design. Thus, it is imperative to understand differences and similarities among programmed cell death events regarding their associations with redox imbalance for improved control over these events in malignant cells as well as appropriate design on therapeutic approaches relying on redox control. This review addresses these issues and concludes by bringing affront cold atmospheric plasma as an emerging redox controller with translational potential in clinics.

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.

Apoptotic mechanism activated by blue light and cisplatinum in cutaneous squamous cell carcinoma cells

New approaches are being studied for the treatment of skin cancer. It has been reported that light combined with cisplatinum may be effective against skin cancer. In the present study, the effects of specific light radiations and cisplatinum on A431 cutaneous squamous cell carcinoma (cSCC) and HaCaT non-tumorigenic cell lines were investigated. Both cell lines were exposed to blue and red light sources for 3 days prior to cisplatinum treatment. Viability, apoptosis, cell cycle progression and apoptotic-related protein expression levels were investigated. The present results highlighted that combined treatment with blue light and cisplatinum was more effective in reducing cell viability compared with single treatments. Specifically, an increase in the apoptotic rate was observed when the cells were treated with blue light and cisplatinum, as compared to treatment with blue light or cisplatinum alone. Combined treatment with blue light and cisplatinum also caused cell cycle arrest at the S phase. Treatment with cisplatinum following light exposure induced the expression of apoptotic proteins in the A431 and HaCaT cell lines, which tended to follow different apoptotic mechanisms. On the whole, these data indicate that blue light combined with cisplatinum may be a promising treatment for cSCC.

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.

The genetic landscapes of urological cancers and their clinical implications in the era of high-throughput genome analysis

OBJECTIVE

With the advent of high-throughput genome analysis, we are increasingly able to sequence and hence understand the pathogenic processes underlying individual cancers. Recently, consortiums such as The Cancer Genome Atlas (TCGA) have performed large-scale projects to this end, providing significant amounts of information regarding the genetic landscapes of several cancers.

PATIENTS AND METHODS

We performed a narrative review of studies from the TCGA and other major studies. We aimed to summarise data exploring the clinical implications of specific genetic alterations, both prognostically and therapeutically, in four major urological cancers. These were renal cell carcinoma, muscle-invasive bladder cancer/carcinoma, prostate cancer, and testicular germ cell tumours.

RESULTS

With these four urological cancers, great strides have been made in the molecular characterisation of tumours. In particular, recent studies have focussed on identifying molecular subtypes of tumours with characteristic genetic alterations and differing prognoses. Other prognostic alterations have also recently been identified, including those pertaining to epigenetics and microRNAs. In regard to treatment, numerous options are emerging for patients with these cancers such as including immune checkpoint inhibition, epigenetic-based treatments, and agents targeting MAPK, PI3K, and DNA repair pathways. There are a multitude of trials underway investigating the effects of these novel agents, the results of which are eagerly awaited.

CONCLUSIONS

As medicine chases the era of personalised care, it is becoming increasingly important to provide individualised prognoses for patients. Understanding how specific genetic alterations affects prognosis is key for this. It will also be crucial to provide highly targeted treatments against the specific genetics of a patient's tumour. With work performed by the TCGA and other large consortiums, these aims are gradually being achieved. Our review provides a succinct overview of this exciting field that may underpin personalised medicine in urological oncology.

Immune checkpoint inhibitors in genitourinary malignancies

Although immune-mediated therapies have been used in genitourinary (gu) malignancies for decades, recent advances with monoclonal antibody checkpoint inhibitors (cpis) have led to a number of promising treatment options. In renal cell carcinoma (rcc), cpis have been shown to have benefit over conventional therapies in a number of settings, and they are the standard of care for many patients with metastatic disease. Based on recent data, combinations of cpis and antiangiogenic therapies are likely to become a new standard approach in rcc. In urothelial carcinoma, cpis have been shown to have a role in the second-line treatment of metastatic disease, and a number of clinical trials are actively investigating cpis for other indications. In other gu malignancies, such as prostate cancer, results to date have been less promising. Immunotherapies continue to be an area of active study for all gu disease sites, with several clinical trials ongoing. In this review, we summarize the current evidence for cpi use in rcc, urothelial carcinoma, prostate cancer, testicular germ-cell tumours, and penile carcinoma. Ongoing clinical trials of interest are highlighted, as are the challenges that clinicians and patients will potentially face as immune cpis become a prominent feature in the treatment of gu cancers.

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.

Therapeutic Challenges for Cisplatin-Resistant Ovarian Germ Cell Tumors

The majority of patients with advanced ovarian germ cell cancer are treated by cisplatin-based chemotherapy. Despite adequate first-line treatment, nearly one third of patients relapse and almost half develop cisplatin-resistant disease, which is often fatal. The treatment of cisplatin-resistant disease is challenging and prognosis remains poor. There are limited data on the efficacy of specific chemotherapeutic regimens, high-dose chemotherapy with autologous progenitor cell support and targeted therapies. The inclusion of patients in clinical trials is strongly recommended, especially in clinical trials on the most frequent male germ cell tumors, to offer wider therapeutic opportunities. Here, we provide an overview of current and potential new treatment options including combination chemotherapy, high-dose chemotherapy and molecular targeted therapies, for patients with cisplatin-resistant ovarian germ cell tumors.

Targeted treatment approaches in refractory germ cell tumors

Germ cell tumors (GCTs) are the most common type of solid tumor amongst patients between 15 and 35 years of age. They are also one of the types of tumor with the highest cure rate, due to their high sensitivity to cisplatin based chemotherapy. Nonetheless, around 15-20% of metastatic patients will not have curative options after a relapse on the first and second line. This proves that new therapeutic options for these refractory GCTs patients need to be developed. This article offers a bibliographic review of all studies using targeted treatment or immunotherapy for refractory GCTs 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.

IGF signalling in germ cells and testicular germ cell tumours: roles and therapeutic approaches

The insulin-like growth factor (IGF) axis plays key roles in normal tissue growth and development as well as in the progression of several tumour types and their subsequent growth and progression to a metastatic phenotype. This review explores the role of IGF system in normal germ cell development and function in addition to examining the evidence for deregulation of IGF signalling in cancer, with particular relevance to evidence supporting a role in testicular germ cell tumours (TGCTs). Despite the clear preclinical rationale for targeting the IGF axis in cancer, there has been a lack of progress in identifying which patients may benefit from such therapy. Future employment of agents targeting the IGF pathway is expected to concentrate on their use in combination with other treatments to prevent resistance and exploit their potential as chemo- and radiosensitizers.

Phase II study of avelumab in multiple relapsed/refractory germ cell cancer

Background Germ cell tumors (GCTs) are highly curable diseases; however, not all patients can be cured. Patients in their second relapse have especially poor prognoses. PD-L1 expression is significantly higher in GCTs than in normal testicular tissue, and high PD-L1 expression is associated with a poor prognosis. This study aimed to determine the efficacy and safety of avelumab, a PD-L1 inhibitor, in patients with GCTs. Methods In this phase 2 study, patients with multiple relapsed and/or refractory GCTs were treated with avelumab at a dose of 10 mg/kg administered biweekly until progression or unacceptable toxicity. The primary endpoint was 12-week progression-free survival (PFS). Fifteen evaluable patients had to be enrolled in the first cohort, and if <8 of 15 patients had 12-week PFS, the study was to be terminated. Here, we report the results of the first stage of the trial. Results From November 2017 to January 2018, 8 patients with a median age of 29 years (range, 22 to 52 months) were enrolled. Patients were pretreated with a median of 5 (range, 1 to 6) previous lines of platinum-based therapies; 5 tumors (62.5%) were absolutely refractory to cisplatin, and 5 patients (62.5%) had visceral nonpulmonary metastases. At a median follow-up period of 2.6 months (range, 0.3 to 14.4), all the patients experienced disease progression, and 7 patients (87.5%) died. The twelve-week PFS was 0%, median PFS was 0.9 months (95% CI 0.5-1.9), and median OS was 2.7 months (95% CI 1.0-3.3). Avelumab was well tolerated, and no severe adverse events were observed. Conclusions This study failed to achieve its primary endpoint. Our data suggest a lack of avelumab efficacy in unselected multiple relapsed/refractory GCTs.

Testicular germ cell tumor: a comprehensive review

Testicular tumors are the most common tumors in adolescent and young men and germ cell tumors (TGCTs) account for most of all testicular cancers. Increasing incidence of TGCTs among males provides strong motivation to understand its biological and genetic basis. Gains of chromosome arm 12p and aneuploidy are nearly universal in TGCTs, but TGCTs have low point mutation rate. It is thought that TGCTs develop from premalignant intratubular germ cell neoplasia that is believed to arise from the failure of normal maturation of gonocytes during fetal or postnatal development. Progression toward invasive TGCTs (seminoma and nonseminoma) then occurs after puberty. Both inherited genetic factors and environmental risk factors emerge as important contributors to TGCT susceptibility. Genome-wide association studies have so far identified more than 30 risk loci for TGCTs, suggesting that a polygenic model fits better with the genetic landscape of the disease. Despite high cure rates because of its particular sensitivity to platinum-based chemotherapy, exploration of mechanisms underlying the occurrence, progression, metastasis, recurrence, chemotherapeutic resistance, early diagnosis and optional clinical therapeutics without long-term side effects are urgently needed to reduce the cancer burden in this underserved age group. Herein, we present an up-to-date review on clinical challenges, origin and progression, risk factors, TGCT mouse models, serum diagnostic markers, resistance mechanisms, miRNA regulation, and database resources of TGCTs. We appeal that more attention should be paid to the basic research and clinical diagnosis and treatment of TGCTs.

Managing seminomatous and nonseminomatous germ cell tumors

PURPOSE OF REVIEW

In the present review, we summarize the recent developments in the management of germ cell tumors (GCTs).

RECENT FINDINGS

Treatment-related acute and late-onset toxicity remains a key challenge in the management of GCTs, with recent evidence showing that the adverse health outcomes of etoposide and cisplatin for four cycles in comparison to bleomycin, etoposide, and cisplatin for three cycles appear to be similar. Recent data showed that multidisciplinary clinic approach and management in experienced academic centers were associated with improved overall survival in GCT patients. There are currently multiple conventional-dose chemotherapy options for salvage therapy in patients with refractory or recurrent disease. In addition, more efficacious high-dose chemotherapy regimens continue to be developed. The role of salvage conventional-dose chemotherapy versus high-dose chemotherapy is currently being investigated prospectively. Recent reports suggested that brentuximab vedotin could be a potential salvage option for cluster of differentiation 30 positive refractory GCTs. On the other hand the results of the first phase II clinical trial investigating pembrolizumab in refractory GCTs were disappointing showing no clinical activity.Finally, deep exploration of the immune profile of GCTs using immunohistochemistry and gene expression profiling has identified that advanced GCT stage was associated with decreased T-cell and Natural killer-cell signatures, whereas T regulatory, neutrophil, mast cell, and macrophage signatures increased with advanced stage. Even though these results indicated that activated T-cell infiltration correlated with seminoma histology and good prognosis, and could be used in the future as a biomarker, this approach needs to be validated in a large cohort.

SUMMARY

Remaining challenges to be addressed include minimizing therapeutic toxicity, and improving outcomes in patients with refractory/recurrent GCTs.

Epigenetic treatment combinations to effectively target cisplatin-resistant germ cell tumors: past, present, and future considerations

BACKGROUND

Type II germ cell tumors represent the most common solid malignancy in men aged 15-45 years. Despite high cure rates of >90% over all stages, 10-15% of advanced patients develop treatment resistance and potentially succumb to their disease. Treatment of refractory germ cell tumors remains unsatisfactory, and new approaches are needed to further improve outcomes.

OBJECTIVES

With this narrative review, we highlight epigenetic mechanisms related to resistance to standard systemic treatment, which may act as promising targets for novel combined epigenetic treatment approaches.

MATERIALS AND METHODS

A comprehensive literature search of PubMed and MEDLINE was conducted to identify original and review articles on resistance mechanisms and/or epigenetic treatment of germ cell tumors in vitro and in vivo. Review articles were hand-searched to identify additional articles.

RESULTS

Distinct epigenetic phenomena have been linked to chemotherapy resistance in germ cell tumors, among which DNA hypermethylation, histone acetylation, and bromodomain proteins appear as promising targets for therapeutic exploitation. Inhibitors of key regulators, for example DNA methyltransferases (e.g. decitabine, guadecitabine), histone deacetylases (e.g. romidepsin), and bromodomain proteins (e.g. JQ1) decreased cell viability, triggered apoptosis, and growth arrest. Additionally, these epigenetic drugs induced differentiation and led to loss of pluripotency and re-sensitization towards cisplatin in cell lines and animal models.

DISCUSSION

Epigenetic treatments hold promise to (i) reduce the treatment burden of and (ii) overcome resistance to standard cisplatin-based chemotherapy. Combined approaches may enhance activity, while the ideal target and treatment combination of epigenetic drugs, either with another epigenetic agent or conventional cytotoxic agents need to be defined.

CONCLUSION

Epigenetic (combination) treatment for germ cell tumors should be further explored in pre-clinical and clinical research for its potential to further improve germ cell tumor treatment.

Current pharmacotherapy for testicular germ cell cancer

INTRODUCTION

With the implementation of platinum-based chemotherapy, germ cell tumors (GCTs) became a model for a curable solid tumor, with survival rates of 95% in all patients with >80% survival in metastatic stages.

AREAS COVERED

Herein, the authors review the current standards of adjuvant chemotherapy for stage I GCTs as well as first-line and salvage treatments for metastatic disease. Novel approaches for refractory disease are also reviewed.

EXPERT OPINION

Active surveillance should be considered for all stage I patients and is the preferred approach for stage I seminoma. In stage I non-seminomas with vascular invasion, one cycle of bleomycin, etoposide, and cisplatin (BEP) substantially reduces the relapse risk. For most advanced GCTs, BEP remains the first-line standard of care. For poor prognosis disease treatment, stratification according to tumor marker decline is recommended. The role of primary high-dose chemotherapy (HDCT) for selected very high-risk patients remains to be prospectively evaluated. Salvage HDCT at relapse seems superior to conventional chemotherapy, retrospectively. The treatment of multiply relapsed disease remains challenging. The gemcitabine/oxaliplatin/paclitaxel (GOP) protocol is considered the standard for refractory disease. However, overall, outcomes are poor and new treatment approaches are urgently needed with targeted therapies so far failing to yield relevant clinical activity.

Exploitation of Precision Medicine Trials Data: Examples of Long Responders From the SHIVA01 Trial

Purpose

Precision medicine trials constitute a precious source of molecular data with prospective clinical annotations allowing the exploration of patients’ subpopulations according to specific clinical or biological questions. Using the SHIVA01—the first randomized trial comparing molecularly targeted therapy on the basis of tumor molecular profiling versus conventional chemotherapy in metastatic cancer patients who failed standard of care therapy—annotated database, we report cases of patients treated in the trial with targeted therapy who experienced an objective response or prolonged disease stabilization in light of patients’ molecular alterations.

Patients and Methods

We selected all patients included in SHIVA01 treated with a molecularly targeted agent (MTA) who experienced an objective response or disease stabilization that lasted longer than 6 months according to Response Evaluation Criteria in Solid Tumors version 1.1.

Results

Among the 170 patients who received MTAs in the SHIVA01 trial, 15 patients (9%) experienced an objective response (n = 3) or disease stabilization that lasted longer than 6 months (n = 12). The most frequent histologic subtypes were breast cancer (27%) and cervical cancer (20%). Six patients, including three patients with breast cancer, were treated with abiraterone on the basis of androgen receptor protein overexpression. Five patients were treated with everolimus on the basis of a PTEN heterozygous deletion with loss of protein expression, PIK3CA mutation, or both alterations. The remaining four patients were treated with tamoxifen, erlotinib, imatinib, and vemurafenib on the basis of progesterone receptor expression, EGFR amplification, KIT mutation, and BRAF mutation, respectively. TP53 mutations were absent in responder patients.

Conclusion

Analysis of patients who experienced objective responses or disease stabilization that lasted longer than 6 months allowed the identification of potential biomarkers of sensitivity and resistance to MTAs.

Molecular Mechanisms of Cisplatin Chemoresistance and Its Circumventing in Testicular Germ Cell Tumors

PURPOSE OF REVIEW

Testicular germ cell tumors (TGCTs) represent the most common solid tumors affecting young men. Majority of TGCTs respond well to cisplatin-based chemotherapy. However, patients with refractory disease have limited treatment modalities associated with poor prognosis. Here, we discuss the main molecular mechanisms associated with acquired cisplatin resistance in TGCTs and how their understanding might help in the development of new approaches to tackle this clinically relevant problem. We also discuss recent data on the strategies of circumventing the cisplatin resistance from different tumor types potentially efficient also in TGCTs.

RECENT FINDINGS

Recent data regarding deregulation of various signaling pathways as well as genetic and epigenetic mechanisms in cisplatin-resistant TGCTs have contributed to understanding of the mechanisms related to the resistance to cisplatin-based chemotherapy in these tumors. Understanding of these mechanisms enabled explaining why majority but not all TGCTs patients are curable with cisplatin-based chemotherapy. Moreover, it could lead to the development of more effective treatment of refractory TGCTs and potentially other solid tumors resistant to platinum-based chemotherapy. This review provides additional insights into mechanisms associated with cisplatin resistance in TGCTs, which is a complex phenomenon, and there is a need for novel modalities to overcome it.

Everolimus in patients with multiply relapsed or cisplatin refractory germ cell tumors: results of a phase II, single-arm, open-label multicenter trial (RADIT) of the German Testicular Cancer Study Group

BACKGROUND

Treatment options for patients (pts) with multiply relapsed or refractory metastatic germ cell cancer (GCC) are limited. The mTOR inhibitor everolimus has been approved for the treatment of different solid tumors and was assessed in refractory GCC within this phase II RADIT trial of the German Testicular Cancer Study Group.

METHODS

GCC pts progressing during cisplatin-based salvage chemotherapy, or relapsing after high-dose chemotherapy, or failing at least two lines of cisplatin-based chemotherapy were eligible. Prior combination chemotherapy with gemcitabine, oxaliplatin and paclitaxel, or a doublet combination of these drugs was mandatory. Primary endpoint was the progression-free survival rate at 12 weeks. Twenty-five evaluable pts were needed, assuming a 20% two-sided type 1 error and 95% power to reject the null hypothesis of 5% of patients being progression-free after 12 weeks. At least one pt among the first 13 pts being progression-free after 6 weeks was mandatory to complete recruitment. Secondary endpoints were objective response rate, disease control rate (SD + PR + CR), median progression-free survival (PFS), median overall survival (OS), and safety. The trial was registered at http://clinicaltrials.gov as NCT01242631.

RESULTS

Twenty-five pts from six German centers were treated with everolimus 10 mg orally once daily until disease progression or unacceptable toxicity between December 2010 and January 2014. 12-week PFS rate was 0%, no objective responses were achieved, and only one pt had stable disease after 6 weeks on treatment as a prerequisite of completing patient accrual accounting for a 6-week disease control rate of 5.4%. Median PFS and OS were estimated at 7.4 weeks and 8.3 weeks, respectively. Toxicity was acceptable, with one treatment discontinuation due to adverse events, and no new safety signals detected.

CONCLUSIONS

Targeting the mTOR pathway with single-agent everolimus failed to produce clinically relevant responses in pts with heavily pretreated and/or cisplatin-refractory GCC.

Management of Refractory Germ Cell Cancer

Over the past 5 decades, the use of well-validated, guideline-based strategies has resulted in high cure rates in newly diagnosed patients with germ cell cancer. However, about 30% of those with metastatic disease at initial presentation will experience refractory disease. Salvage treatment is far more complex and less validated than first-line treatment because it is rare, patient cohorts are more heterogeneous, and prognostic factors seem to have greater impact. Prior to the initiation of any salvage treatment, several considerations must be made, including assessment of known prognostic factors and choice of the optimal salvage strategy. Evaluation of patients according to their disease biology, response to prior treatment, and the extent of their tumor burden at the time of salvage treatment is crucial for establishing the optimal salvage strategy. Patients with metastatic germ cell cancer in whom adequate cisplatin-based first-line chemotherapy fails should be included in the ongoing randomized TIGER trial comparing conventional-dose chemotherapy with high-dose chemotherapy as first salvage treatment. Outside this trial, patients may be treated with conventional or high-dose chemotherapy depending on the presence or absence of adverse prognostic factors, availability of resources, and patient and physician preferences.

Therapeutic approaches for refractory germ cell cancer

INTRODUCTION

Most germ cell cancer patients with metastatic disease are cured by cisplatin-based combination chemotherapy. 30% of metastatic patients will develop relapse or progress despite adequate first-line treatment and will require salvage therapy, with about 10% of metastasized patients ultimately developing platinum-resistant and fatal disease. Areas covered: Based on a comprehensive literature search of MEDLINE, EMBASE and conference proceedings of ESMO, ASCO and EAU meetings, this review provides an overview on current and potential future treatment options for platinum-refractory germ cell cancer patients including cytostatics and molecularly targeted therapies. Expert commentary: Treatment of platinum-refractory disease remains challenging and long-term survival is rarely achieved despite multimodal treatment approaches. Targeted treatment approaches do not yet play a role in the treatment of platinum-refractory disease due to lacking efficacy in small, unselected clinical trials. Inclusion of patients into clinical trials is strongly recommended.

Will Testicular Germ Cell Tumors Remain Untargetable?

Testicular Germ cell tumors (TGCT) represent the most common solid tumors affecting young men. They constitute a distinct entity because of their embryonic origin and their unique biological behavior. Recently, new preclinical data on genetic and epigenetic susceptibility profiles, biological signaling machinery as well as on molecular patterns of tumors and pathways of pathogenesis helped to elucidate the pathogenesis and the differentiation of TGCTs and to understand the mechanisms behind the development of resistance to treatment. In the present work, we have reviewed new clues to the development, differentiation and progression of TGCTs. We focus on the most important epigenetic and molecular biomarkers, and discussed their diagnostic and prognostic accuracy compared to the currently used biomarkers. The mechanisms underlying the development of resistance to cisplatin and commonly used chemotherapeutic agents are also discussed in detail. Finally, we summarize failed and ongoing clinical trials using targeted therapies in resistant TGCTs, and analyze the potential of new targeted therapies.

Current Management of Refractory Germ Cell Tumors and Future Directions

PURPOSE OF REVIEW

We review current management strategies for patients with relapsed and refractory germ cell tumors (GCTs), defined as relapsed or persistent disease following at least one line of cisplatin-based chemotherapy. Additionally, we discuss future directions in the management of these patients.

RECENT FINDINGS

Recent studies involving targeted therapies have been disappointing. Nevertheless, studies of the management of refractory germ cell cancer are ongoing, with a focus on optimal utilization of high-dose chemotherapy and autologous stem cell transplant, as well as the role of immune checkpoint inhibitors in refractory germ cell tumors. Studies aiming to identify those patients who may benefit from more intensive treatment up front to prevent the development of refractory disease are also in progress. Testicular germ cell tumors are among the most curable of all solid tumor malignancies, with cure being possible even in the refractory, metastatic setting. Treatment of refractory disease remains a challenging clinical scenario, but potentially practice changing studies are ongoing.

Role of Akt-independent mTORC1 and GSK3β signaling in sublethal NMDA-induced injury and the recovery of neuronal electrophysiology and survival

Glutamate-induced excitotoxicity, mediated by overstimulation of N-methyl-D-aspartate (NMDA) receptors, is a mechanism that causes secondary damage to neurons. The early phase of injury causes loss of dendritic spines and changes to synaptic activity. The phosphatidylinositol-4,5-bisphosphate 3-kinase/Akt/ mammalian target of rapamycin (PI3K/Akt/mTOR) pathway has been implicated in the modulation and regulation of synaptic strength, activity, maturation, and axonal regeneration. The present study focuses on the physiology and survival of neurons following manipulation of Akt and several downstream targets, such as GSK3β, FOXO1, and mTORC1, prior to NMDA-induced injury. Our analysis reveals that exposure to sublethal levels of NMDA does not alter phosphorylation of Akt, S6, and GSK3β at two and twenty four hours following injury. Electrophysiological recordings show that NMDA-induced injury causes a significant decrease in spontaneous excitatory postsynaptic currents at both two and twenty four hours, and this phenotype can be prevented by inhibiting mTORC1 or GSK3β, but not Akt. Additionally, inhibition of mTORC1 or GSK3β promotes neuronal survival following NMDA-induced injury. Thus, NMDA-induced excitotoxicity involves a mechanism that requires the permissive activity of mTORC1 and GSK3β, demonstrating the importance of these kinases in the neuronal response to injury.

Judicious Toggling of mTOR Activity to Combat Insulin Resistance and Cancer: Current Evidence and Perspectives

The mechanistic target of rapamycin (mTOR), via its two distinct multiprotein complexes, mTORC1, and mTORC2, plays a central role in the regulation of cellular growth, metabolism, and migration. A dysregulation of the mTOR pathway has in turn been implicated in several pathological conditions including insulin resistance and cancer. Overactivation of mTORC1 and disruption of mTORC2 function have been reported to induce insulin resistance. On the other hand, aberrant mTORC1 and mTORC2 signaling via either genetic alterations or increased expression of proteins regulating mTOR and its downstream targets have contributed to cancer development. These underlined the attractiveness of mTOR as a therapeutic target to overcome both insulin resistance and cancer. This review summarizes the evidence supporting the notion of intermittent, low dose rapamycin for treating insulin resistance. It further highlights recent data on the continuous use of high dose rapamycin analogs and related second generation mTOR inhibitors for cancer eradication, for overcoming chemoresistance and for tumor stem cell suppression. Within these contexts, the potential challenges associated with the use of mTOR inhibitors are also discussed.

Platinum-refractory germ cell tumors: an update on current treatment options and developments

PURPOSE

In general, 50 % up to 80 % of metastasized germ cell tumor patients can be cured by platinum-based chemotherapy. However, 3-5 % of patients will still die of platinum-refractory disease and new systemic treatment options are needed to improve treatment success in this difficult setting. This review aims to give an overview on treatment options and current developments in the field of platinum-refractory male germ cell tumors.

METHODS

A comprehensive literature search was conducted searching PubMed, Medline, Cochrane and Embase to identify clinical trials regarding the treatment of platinum-refractory disease. ASCO, EAU and ESMO conference proceedings were searched to identify unpublished results of relevant trials. Comprehensive review papers were hand searched for additional references. Clinicaltrials.gov was checked for ongoing clinical trials in the field of platinum-refractory germ cell tumors.

RESULTS

Outcome of platinum-refractory disease remains poor. Single-agents with reasonable activity are gemcitabine, oxaliplatin and paclitaxel, but complete remissions resulting in long-term survival could not be achieved. The triple-combination of gemcitabine, oxaliplatin and paclitaxel followed by resection of residual masses provides the best outcomes with objective responses in 51 % of patients and long-term survival in approximately 10-15 %. To date, no molecularly targeted agent has shown reasonable activity.

CONCLUSIONS

Treatment options for platinum-refractory disease are limited, but a small subset of patients may achieve long-term disease-free survival by multimodal treatment. The potential of novel targeted agents, i.e. by immune-checkpoint-inhibition remains to be defined.

Investigational targeted therapies for the treatment of testicular germ cell tumors

INTRODUCTION

Germ cell tumors (GCTs) are the most common malignancy among men aged between 15 to 45. Despite high cure rates of >90% over all GCTs, 3 to 5% of patients will still die of platinum-refractory disease. New systemic treatment options are needed to improve treatment success in this challenging setting.

AREAS COVERED

To review targeted treatment options and preclinical developments in platinum-refractory GCTs, a comprehensive literature search of PubMed, Medline and scientific meeting abstracts on published clinical trials and reports on molecularly targeted approaches was conducted. Outcomes of platinum-refractory disease and of patients failing high-dose chemotherapy remain poor. Currently, no molecularly targeted treatment has shown clinically meaningful activity in unselected patient populations in clinical trials, but individual patients may achieve short-lived objective responses by treatment with sunitinib, brentuximab vedotin or imatinib. Targeted trials based on molecular selection of patients have not yet been performed.

EXPERT OPINION

The limited activity of targeted agents in refractory GCT is disappointing. Assessment of druggable biomarkers and marker-stratified treatment may help individual patients, but is largely lacking. The low incidence and high curability of GCTs make the design of larger clinical trials difficult. The potential of novel agents, i.e. immune-checkpoint inhibitors, remains to be elucidated.