Alkylating agents-induced gonadotoxicity in prepubertal males: Insights on the clinical and preclinical front

Rising cure rates in pediatric cancer patients warrants an increased attention toward the long-term consequences of the diagnosis and treatment in survivors. Chemotherapeutic agents can be gonadotoxic, rendering them at risk for infertility post-survival. While semen cryopreservation is an option that can be provided for most (post)pubertal boys before treatment, this is unfortunately not an option prepubertal in age, simply due to the lack of spermatogenesis. Over the last couple of years, studies have thus focused on better understanding the testis niche in response to various chemotherapeutic agents that are commonly administered and their direct and indirect impact on the germ cell populations. These are generally compounds that have a high risk of infertility and have been classified into risk categories in curated fertility guidelines. However, with it comes the lack of evidence and the challenge of using informative models and conditions most reflective of the physiological scenario, in short, the appropriate study designs for clinically relevant outcomes. Besides, the exact mechanism(s) of action for many of these "risk" compounds as well as other agents is unclear. Understanding their behavior and effect on the testis niche will pave the way for incorporating new strategies to ultimately combat infertility. Of the various drug classes, alkylating agents pose the highest risk of gonadotoxicity as per previously established studies as well as risk stratification guidelines. Therefore, this review will summarize the findings in the field of male fertility concerning gonadotoxicity of akylating agents as a result of chemotherapy exposure.

Effect of Neuroendocrine Neoplasm Treatment on Human Reproductive Health and Sexual Function

Neuroendocrine neoplasms (NEN) are characterized by a wide clinical heterogeneity and biological variability, with slow progression and long survival in most cases. Although these tumors can affect young adults, there are few studies that focus on the sexual and reproductive system. The aim of this review was to evaluate the effect of NEN treatment, including somatostatin analogues (SSA), targeted therapy (Everolimus and Sunitinib), radiolabeled-SSA and chemotherapy, on male and female reproductive systems and sexual function. This narrative review was performed for all available prospective and retrospective studies, case reports and review articles published up to March 2022 in PubMed. To date, few data are available on the impact of SSA on human fertility and most of studies come from acromegalic patients. However, SSAs seem to cross the blood–placental barrier; therefore, pregnancy planning is strongly recommended. Furthermore, the effect of targeted therapy on reproductive function is still undefined. Conversely, chemotherapy has a well-known negative impact on male and female fertility. The effect of temozolomide on reproductive function is still undefined, even if changes in semen parameters after the treatment have been described. Finally, very few data are available on the sexual function of NEN treatment.

Exposure to Chemotherapy During Childhood or Adulthood and Consequences on Spermatogenesis and Male Fertility

Over the last decade, the number of cancer survivors has increased thanks to progress in diagnosis and treatment. Cancer treatments are often accompanied by adverse side effects depending on the age of the patient, the type of cancer, the treatment regimen, and the doses. The testicular tissue is very sensitive to chemotherapy and radiotherapy. This review will summarize the epidemiological and experimental data concerning the consequences of exposure to chemotherapy during the prepubertal period or adulthood on spermatogenic progression, sperm production, sperm nuclear quality, and the health of the offspring. Studies concerning the gonadotoxicity of anticancer drugs in adult survivors of childhood cancer are still limited compared with those concerning the effects of chemotherapy exposure during adulthood. In humans, it is difficult to evaluate exactly the toxicity of chemotherapeutic agents because cancer treatments often combine chemotherapy and radiotherapy. Thus, it is important to undertake experimental studies in animal models in order to define the mechanism involved in the drug gonadotoxicity and to assess the effects of their administration alone or in combination on immature and mature testis. These data will help to better inform cancer patients after recovery about the risks of chemotherapy for their future fertility and to propose fertility preservation options.

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.

Sperm DNA Damage in Cancer Patients

Fertility is a growing healthcare issue for a rising number of cancer survivors. In men, cancer itself and its treatment can negatively affect spermatogenesis by targeting the dividing spermatogonia and their cellular environment, ultimately leading to a reduction of testicular germ cells and sperm count. Experimental data and prospective longitudinal studies have shown that sperm production can recover after cancer treatment. But despite this, yet unpredictable, recovery in sperm production, cancer survivors are more at risk to produce sperm with aneuploidy, DNA damage, abnormal chromatin structure, and epigenetic defects even 2 years post-treatment. Sperm DNA alteration is of clinical concern, as these patients may father children or seek assisted reproduction technologies (ART) using gametes with damaged genome that could result in adverse progeny outcomes. Interestingly, large cohort studies revealed lower birth rate but no significant impact on the health of the children born from male cancer survivors (naturally or using ART). Nevertheless, a better understanding of how cocktail of chemotherapy and new anticancer agents affect spermatogenesis and sperm quality is needed to reduce side effects. Moreover, developing new fertility preservation strategies is essential as sperm cryopreservation before treatment is currently the only option but does not apply for prepubertal/young postpubertal patients.

Effect of Zinc on Spermatogenesis and Sperm Chromatin Condensation in Bleomycin, Etoposide, Cisplatin Treated Rats

Objective

The incidence rate of testicular cancer among young males is high. Co-administration of bleomycin, etoposide and cisplatin (BEP) has increased survival rate of patients with testicular cancer. Although BEP is one of the most effective treatment for testicular cancer, but it severely affects the reproductive system that ultimately leads to infertility. In addition to its antioxidant activity, zinc has an important role in progression of spermiogenesis. This study aimed to evaluate the effect of zinc on sperm parameters, chromatin condensation and testicular structure after BEP treatment.

Materials and Methods

In this experimental study, 40 male rats were divided into 4 groups (control, BEP, BEP+ zinc and zinc) and examined for 2 spermatogenesis periods (i.e. 18 weeks). The rats in BEP and BEP+ zinc group were treated with BEP at appropriate doses (0.75, 7.5, and 1.5 mg/kg) for three cycles of three weeks. Zinc at a dose of 10 mg/kg/day was administered to BEP+ zinc and zinc groups. After 18 weeks, we assessed sperm parameters, and excessive histone in sperm chromatin using aniline blue staining, as well as testicular structure and germ line cells using periodic acid-Schiff staining.

Results

After BEP treatment, significant decreases were observed in normal sperm morphology, motility, and concentration, as well as alterations in rat sperm chromatin condensation and testicular tissue (P<0.001). Furthermore, after zinc consumption for 9 weeks, we observed significant improvements of sperm parameters and chromatin condensation as well as a significant retrieval of spermatogonia, leydig cells and tubular architecture (P<0.05).

Conclusion

Zinc administration after chemotherapy with BEP in testicular cancer might be potentially useful in declining the off target consequence associated with oxidative stress.

Estrogen, through estrogen receptor 1, regulates histone modifications and chromatin remodeling during spermatogenesis in adult rats

Estrogen receptors (ESR1 and ESR2) play crucial roles in various processes during spermatogenesis. To elucidate individual roles of ESRs in male fertility, we developed in vivo selective ESR agonist administration models. Adult male rats treated with ESR1 and ESR2 agonist for 60 days show spermatogenic defects leading to reduced sperm counts and fertility. While studying epigenetic changes in the male germ line that could have affected fertility, we earlier observed a decrease in DNA methylation and its machinery upon ESR2 agonist treatment. Here, we explored the effects on histone modifications, which could contribute to decreased male fertility upon ESR agonist administration. ESR1 agonist treatment affected testicular levels of histone modifications associated with active and repressed chromatin states, along with heterochromatin marks. This was concomitant with deregulation of corresponding histone modifying enzymes in the testis. In addition, there was increased retention of histones along with protamine deficiency in the caudal spermatozoa after ESR1 agonist treatment. This could be due to the observed decrease in several chromatin remodeling proteins implicated in mediating histone-to-protamine exchange during spermiogenesis. The activating and repressing histone marks in spermatozoa, which play a critical role in early embryo development, were deregulated after both the ESR agonist treatments. Together, these epigenetic defects in the male germ line could affect the spermatozoa quality and lead to the observed decrease in fertility. Our results thus highlight the importance of ESRs in regulating different epigenetic processes during spermatogenesis, which are crucial for male fertility.

[Transgenerational impact of chemotherapy: Would the father exposure impact the health of future progeny?]

The number of cancer survivors is increasing and their quality of life is becoming a major public health issue. Cancer treatments reduce men's reproductive health by targeting spermatogenesis. Ultimately, DNA, chromatin and the epigenome of spermatozoa can be altered in cancer survivors. Knowing whether the history of cancer and the treatments received can have consequences on the health of their offspring is therefore a fundamental question for these patients. This review gathers the experimental and epidemiological evidences of the effects observed on the direct descendants and on several generations, and draws up the state of knowledge on the mechanisms potentially involved. Experimental data describe inter- and transgenerational effects of paternal exposure depending on the type of treatment, dose and time of exposure. In the human population, the analysis of the effects specifically due to chemotherapy is still limited because they are often combined with irradiation treatments. However, it appears that chemotherapy agents affect the birth rate but do not have a significant impact on the health of the children born. Nevertheless, the demonstration of modifications of the sperm epigenome in cancer survivors, even after a period of remission, as well as changes in the sperm of the progeny in animal models, suggests a possible transgenerational transmission that remains to be studied in the human population.

The Effect of a Unilateral Orchiectomy before Gonadotoxic Treatment on the Contralateral Testis in Adult and Prepubertal Rats

PURPOSE

Previous studies have shown that the removal of one testis leads to a compensatory mechanism in the contralateral one, but this was species and age dependent. The aim of this study was to check whether this compensation would still occur after the combination of a unilateral orchiectomy and gonadotoxic treatment, since this resembles the clinical situation of patients who have to undergo highly toxic cancer treatment and therefore choose to cryopreserve a testicular biopsy for fertility restoration purposes.

MATERIALS & METHODS

Sprague Dawley rats underwent either unilateral orchiectomy, gonadotoxic busulfan treatment, the combination of both or served as fertile control. A comparison of the compensatory effects was made between adult and prepubertal treated rats. Mating experiments were performed, testosterone levels were followed-up, testicular weight was recorded and histology was analysed.

RESULTS

Adult treated rats were able to restore fertility spontaneously in all treatment groups. On the other hand, 30% of the rats that underwent a unilateral orchiectomy and gonadotoxic treatment at prepubertal age showed hampered spermatogenesis, low testosterone levels, decreased testicular weights and were not able to reproduce.

CONCLUSION

This study emphasizes the need of fertility preservation strategies in prepubertal patients before gonadotoxic interventions.

The Effects of Chemotherapeutic Agents, Bleomycin, Etoposide, and Cisplatin, on Chromatin Remodeling in Male Rat Germ Cells

The coadministration of bleomycin, etoposide, and cisplatin (BEP) has increased the survival rate of testicular cancer patients to over 90%. Previous studies have demonstrated that BEP induces germ cell damage during the final stages of spermatogenesis, when major chromatin remodeling occurs. Chromatin remodeling permits histone-protamine exchange, resulting in sperm head chromatin compaction. This process involves different epigenetic modifications of the core histones. The objective of these studies was to investigate the effects of BEP on epigenetic modifications to histones involved in chromatin remodeling. Brown Norway rats were treated with BEP, and their testes were removed to isolate pachytene spermatocytes and round spermatids by unit gravity sedimentation. Western blot analyses were conducted on extracted proteins to detect the expression of key modified histones. In a second cohort testes were prepared for immunohistochemical analysis. The stage-specific expression of each modified histone mark in rat spermatogenesis suggests the involvement of these modifications in chromatin remodeling. BEP treatment significantly increased expression of H3K9m and decreased that of tH2B (or Hist1h2ba) in pachytene spermatocytes, suggesting that nucleosomes were not destabilized to allow for transcription of genes involved in chromatin remodeling. Moreover, BEP treatment altered the expression of H4K8ac in round and elongating spermatids, suggesting that histone eviction was compromised, leading to a looser chromatin structure in mature spermatozoa. Less-compacted sperm chromatin, with alterations to the sperm epigenome, may have an adverse effect on male fertility.

Genetic Effect of Chemotherapy Exposure in Children of Testicular Cancer Survivors

PURPOSE

Cancer survivors express anxiety that chemotherapy exposure may lead to transmissible genetic damage in posttreatment children. Preclinical models suggest that chemotherapy exposure may result in considerable genomic alterations in postexposure progeny. Epidemiologic studies have not demonstrated a significant increase in congenital abnormalities in posttreatment children of cancer survivors, but the inherited genome-wide effect of chemotherapy exposure in humans is unknown.

EXPERIMENTAL DESIGN

Two testicular cancer survivors cured with chemotherapy who had children pre- and postexposure without sperm banking were identified. Familial germline whole genome sequencing (WGS) was performed for these families, and analytic methods were utilized to identify de novo alterations, including mutations, recombinations, and structural rearrangements in the pre- and postexposure offspring.

RESULTS

No increase in de novo germline mutations in postexposure children compared with their preexposure siblings was found. Furthermore, there were no increased short insertion/deletions, recombination frequency, or structural rearrangements in these postexposure children.

CONCLUSIONS

In two families of male cancer survivors, there was no transmissible genomic impact of significant mutagenic exposure in postexposure children. This study may provide possible reassuring evidence for patients undergoing chemotherapy who are unable to have pretreatment sperm cryopreservation. Expanded cohorts that utilize WGS to identify environmental exposure effects on the inherited genome may inform the generalizability of these results. Clin Cancer Res; 22(9); 2183-9. ©2015 AACR.

Effects of bleomycin, etoposide and cisplatin treatment on Leydig cell structure and transcription of steroidogenic enzymes in rat testis

Cytotoxic anticancer chemotherapy affects pituitary-testicular hormonal axis in humans and in animals. This study investigated the effects on Leydig cells of three cycles of bleomycin, etoposide and cisplatin (0.75, 7.5, and 1.5mg/kg, respectively; BEP) chemotherapy in rat testis. The chemotherapy has induced hyperplasia of and degenerative changes in Leydig cells at the end of BEP exposure, which remained so even after a recovery time of 63 days. The increased testicular oxidative stress at the end of the chemotherapy returned to normal level after the recovery time. The chemotherapy has stimulated the transcription of scavenger receptor class type-B1 (SCARB1), steroidogenic acute-regulatory protein (StAR), cytochrome P450 cholesterol side-chain cleavage (CYP11A1), CYP17A1, and inhibited that of 17β-hydroxysteroid dehydrogenase (HSD17B6) and CYP19A1 in association with increased cholesterol and decreased testosterone levels. Even after the recovery time, the chemotherapy still had inhibitory effects on the transcription of all of the above genes in addition to luteinizing hormone receptor and HSD3B1, but not on the StAR gene. The cholesterol and testosterone levels also did not show any significant differences with the control group. The decreased testosterone level at the end of chemotherapy was probably due to inhibition of HSD3B1 and HSD17B6 genes. In conclusion, clinically relevant dose-levels and treatment protocols of BEP chemotherapy adversely affect Leydig cell function. The BEP chemotherapy inhibits the transcription of steroidogenic enzymes and that these effects sustain over an extended period of time without returning to normal levels.