Targeted therapies in germ cell tumors

Testis developmental related gene 1 regulates the chemosensitivity of seminoma TCam-2 cells to cisplatin via autophagy

We previously identified testis developmental related gene 1 (TDRG1), a gene implicated in proliferation of TCam-2 seminoma cells. Recent evidence has revealed that autophagy influences the chemosensitivity of cancer cells to chemotherapy. However, whether TDRG1 protein regulates autophagy in seminoma cells and influences their sensitivity to cis-dichlorodiammine platinum (CDDP) remains unknown. In this study, we used TCam-2 cells and male athymic BALB/c nude mice with xenografts of TCam-2 cells to investigate autophagy, cell viability, apoptosis and the p110β/Rab5/Vps34 (PI3-kinase Class III) pathway under the conditions of TDRG1 overexpression or knockdown and with or without CDDP treatment. We found that TDRG1 upregulation promoted autophagy in both TCam-2 cells and seminoma xenografts via p110β/Rab5/Vps34 activation. Inhibition of autophagy reduced cell viability and promoted apoptosis during CDDP treatment of TCam-2 cells. Similarly, TDRG1 knockdown inhibited autophagy, reduced cell viability and promoted apoptosis during CDDP treatment of TCam-2 cells. TDRG1 knockdown inhibited tumour growth and promoted apoptosis in TCam-2 cell xenografts, whereas TDRG1 overexpression had the opposite effect. According to these results, we propose that high expression of TDRG1 promotes autophagy through the p110β/Rab5/Vps34 pathway in TCam-2 cells. TDRG1 overexpression promotes autophagy and leads to CDDP resistance, whereas TDRG1 knockdown inhibits autophagy and promotes chemosensitivity to CDDP both in vivo and in vitro. This study has uncovered a novel role of TDRG1 in reducing chemoresistance during CDDP treatment and provides potential therapeutic strategies for the treatment of human seminoma.

Synthesis of a novel platinum(II) complex with 6,7-dichloro-5,8-quinolinedione and the study of its antitumor mechanism in testicular seminoma

A new platinum(II) complex, [Pt(ClClQ)(DMSO)Cl] (1), utilizing 6,7-dichloro-5,8-quinolinedione (ClClQ) as a ligand, has been synthesized and fully characterized. Single-crystal X-ray diffraction and other spectroscopic and analytical methods revealed that the coordination geometry of Pt(II) in complex 1 can also be described as a four-coordinated square planar geometry. The aim of the study was to explore the in vitro anticancer properties of complex 1. Our studies showed that complex 1 can regulate the viability of testicular seminoma cells in vitro, including cell proliferation and apoptosis. We further observed negative regulation by complex 1 of the expression levels of the key elements in the phosphoinositide-3 kinase (PI3K)/protein kinase B (Akt)/glycogen synthase kinase-3β (GSK3β) pathway, including phosphorylated phosphoinositide-3 kinase (p-PI3K), phosphorylated protein kinase B(p-Akt) and phosphorylated glycogen synthase kinase-3β (p-GSK3β). Moreover, the negative effect of complex 1 was reversed by LiCl, a GSK3β-specific inhibitor of the PI3K signaling pathway. Meanwhile, the levels of Bcl2 associated death promoter (Bad), cytochrome c, active-caspase-3 and active-caspase-9 increased significantly. In conclusion, we observed that complex 1 can regulate the viability of testicular seminoma cells through the PI3K/Akt/GSK3β signaling pathway and the mitochondria-mediated apoptotic pathway in vitro, and thus, complex 1 may have potential for use as a drug in the treatment of testicular germ cell tumors.

Immunotherapy: last bullet in platinum refractory germ cell testicular cancer

Testicular germ cell tumors are chemosensitive with very high cure-rates even in the metastatic setting. However, patients with platinum-refractory and relapsing tumors after autologous stem cell transplant have very poor outcomes despite salvage treatments, and with no effective alternative therapies. Immunotherapy, notably with PD-1 inhibitors, has proven to be very effective in treating various solid tumors. This review summarizes the experience with anti-PD-1 agents (pembrolizumab, nivolumab) in the treatment of testicular germ cell tumor relapsing after multiple lines of treatment, and exposes future trials evaluating newer checkpoint inhibitors in this setting.

Brentuximab-vedotin maintenance following chemotherapy without irradiation for primary intracranial embryonal carcinoma in down syndrome

BACKGROUND

Germ cell tumors (GCT) are the most common central nervous system (CNS) tumors in individuals with Down syndrome. Patients with Down syndrome treated with CNS irradiation are at increased risk of developing cerebrovascular complications such as moyamoya disease. Embryonal carcinoma components are recognized to be more resistant to conventional chemotherapy and radiotherapy and confer a very poor prognosis. CD30 is a member of the tumor necrosis factor-receptor superfamily. CD30+ has a limited expression in normal cells but is the defining marker for embryonal carcinoma. Brentuximab-vedotin is a novel antibody-drug conjugate consisting of the chimeric anti-CD30 antibody conjugated to an anti-tubulin synthetic analog monomethyl auristatin E.

METHODS

A retrospective review of the patient's records was conducted in September 2017.

RESULTS

We report upon our management of a teenage girl with Down syndrome and a suprasellar pure embryonal carcinoma utilizing an intensive chemotherapy regimen followed by brentuximab-vedotin without irradiation. The patient received two cycles of carboplatin and etoposide interspersed with one cycle of cyclophosphamide and etoposide for induction followed by three cycles of marrow-ablative thiotepa and carboplatin rescued by autologous hematopoietic stem cell. Finally, She received six cycles of intravenous brentuximab-vedotin. The patient continues without evidence of recurrent tumor by MRI and tumor marker surveillance 24 months since diagnosis, with no adverse sequelae of her treatment.

CONCLUSIONS

Brentuximab-vedotin may provide a selective and safe alternative (or adjunct) to radiotherapy in the management of patients with CD30-positive CNS embryonal carcinoma, especially for those patients at high risk of developing irradiation-related complications.

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.

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.

TDRG1 regulates chemosensitivity of seminoma TCam-2 cells to cisplatin via PI3K/Akt/mTOR signaling pathway and mitochondria-mediated apoptotic pathway

We previously identified TDRG1 (testis developmental related gene 1), a novel gene with exclusive expression in testis, promoted the proliferation and progression of cultured human seminoma cells through PI3K/Akt/mTOR signaling. As increasing evidence reveal that aberrant activation of this signaling is involved in cisplatin resistance. Then, in this study, we further explored whether TDRG1 regulated the chemosensitivity of seminoma TCam-2 cells to cisplatin. Our researches showed TDRG1 could regulate the viability of TCam-2 cells following cisplatin treatment in vitro through control of both cell apoptosis and cell cycle. Mechanistically, we observed TDRG1 positively regulated the expression levels of the key elements in PI3K/Akt/mTOR pathway including p-PI3K, p-Akt and p-mTOR and also affected the translocation of nuclear p-Akt in TCam-2 cells during cisplatin treatment. Meanwhile, the levels of Bad, cytochrome c, caspase-9 ratio (activated/total), caspase-3 ratio (activated/total) and cleaved-PARP were negatively modulated by TDRG1, which meant the involvement of mitochondria-mediated apoptotic pathway. Furthermore, we found the effect of TDRG1 knockdown or TDRG1 overexpression could be reversed by IGF-1, a PI3K signaling activator, or LY294002, a inhibitor of this pathway, respectively. Similar effects of TDRG1 on cisplatin chemosensitivity and associated molecular mechanism were also confirmed in vivo by employing xenograft assays. In addition, the positive correlation between TDRG1 and p-PI3K, or p-Akt, was found in tumor tissues from seminoma patients. In conclusion, we uncover that TDRG1 regulates chemosensitivity of TCam-2 cells to cisplatin through PI3K/Akt/mTOR signaling and mitochondria-mediated apoptotic pathway both in vitro and in vivo.