Publications by authors named "Leendert Looijenga"

Whilst chemotherapy regimens have proven to be more successful for pediatric cancer patients over the years, their influence on long-term side effects is relatively poorly understood. One of the possible targets is the gonads, with gonadotoxic agents representing those that threaten the patient's ability to have children post surviving the primary disease treatment. Many risk stratification guidelines have categorized these agents based on the severity of their effect on the pre-pubertal testis.

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In patients with proximal hypospadias, often no genetic cause is identified despite extensive genetic testing. Many genes involved in sex development encode transcription factors with strict timing and dosing of the gene products. We hypothesised that there might be recurrent differences in DNA methylation in boys with hypospadias and that these might differ between patients born small versus appropriate for gestational age.

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Liquid biopsies are emerging as an alternative source for pediatric cancer biomarkers with potential applications during all stages of patient care, from diagnosis to long-term follow-up. While developments within this field are reported, these mainly focus on dedicated items such as a specific liquid biopsy matrix, analyte, and/or single tumor type. To the best of our knowledge, a comprehensive overview is lacking.

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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.

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Culture-acquired variants in human pluripotent stem cells (hPSCs) hinder their applications in research and clinic. However, the mechanisms that underpin selection of variants remain unclear. Here, through analysis of comprehensive karyotyping datasets from over 23,000 hPSC cultures of more than 1,500 lines, we explored how culture conditions shape variant selection.

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GCTs are developmental tumors and are likely to reflect ontogenetic and teratogenetic determinants. The objective of this study was to identify syndromes with or without congenital anomalies and non-syndromic defects as potential risk factors. Patients with extracranial GCTs (eGCTs) registered in MAKEI 96/MAHO 98 between 1996 and 2017 were included.

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Objectives: Childhood cancer survivors are at risk for premature ovarian insufficiency, especially after treatment with alkylating agents. The objective of this report is to highlight a case in which this phenomenon caused a false-positive pregnancy test.

Case Presentation: A workup was performed in a 14-year-old girl with a positive pregnancy test.

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Malignant testicular germ cells tumors (TGCTs) are the most common solid cancers in young men. Current TGCT diagnostics include conventional serum protein markers, but these lack the sensitivity and specificity to serve as accurate markers across all TGCT subtypes. MicroRNAs (miRNAs) are small non-coding regulatory RNAs and informative biomarkers for several diseases.

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Background: Small-cell carcinoma of the ovary, hypercalcemic type (SCCOHT) is a rare aggressive ovarian malignancy mainly affecting children, adolescents, and young adults. Since the discovery of mutations in the SMARCA4 gene in 2014, SCCOHT has become the subject of extensive investigation. However, international uniform treatment guidelines for SCCOHT are lacking and the outcome remains poor.

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Germ cell tumors (GCTs) are neoplasms of the testis, ovary and extragonadal sites that occur in infants, children, adolescents and adults. Post-pubertal (type II) malignant GCTs may present as seminoma, non-seminoma or mixed histologies. In contrast, pre-pubertal (type I) GCTs are limited to (benign) teratoma and (malignant) yolk sac tumor (YST).

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Objective: Individuals with 45,X/46,XY or 46,XY gonadal dysgenesis are at increased risk of germ cell malignancies. Therefore, prophylactic bilateral gonadectomy is advised in girls and considered in boys with atypical genitalia for undescended, macroscopically abnormal gonads. However, severely dysgenetic gonads may not contain germ cells rendering gonadectomy unnecessary.

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Pluripotency describes the ability of stem cells to differentiate into derivatives of the three germ layers. In reporting new human pluripotent stem cell lines, their clonal derivatives or the safety of differentiated derivatives for transplantation, assessment of pluripotency is essential. Historically, the ability to form teratomas in vivo containing different somatic cell types following injection into immunodeficient mice has been regarded as functional evidence of pluripotency.

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Article Synopsis
  • Cytokeratin and desmin are proteins linked to Sertoli cell development and testicular germ cell cancer (TGCC), with this study focusing on their expression in normal and cancerous testicular tissue.
  • The study found that desmin is present in Sertoli cells during fetal development but decreases significantly by the second trimester, and it remains in most adult Sertoli cells, even in TGCC cases.
  • Cytokeratin is found in fetal Sertoli cells but absent in adult Sertoli cells, indicating it may signal issues with Sertoli cell maturity, especially in cases of TGCC.
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Neuroblastoma is the most common extracranial solid tumor found in children and despite intense multi-modal therapeutic approaches, low overall survival rates of high-risk patients persist. Tumors with heterozygous loss of chromosome 11q and amplification are two genetically distinct subsets of neuroblastoma that are associated with poor patient outcome. Using an isogenic 11q deleted model system and high-throughput drug screening, we identify checkpoint kinase 1 (CHK1) as a potential therapeutic target for 11q deleted neuroblastoma.

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Objective: The purpose of this study is to report development of a malignant testicular germ cell tumor (GCT) in 2 young adult males with familial male-limited precocious puberty (FMPP) because of LHCGR pathogenic variants in 2 families. Secondarily, to study the possible relation between FMPP and testicular tumors and to investigate whether FMPP might predispose to development of malignant testicular tumors in adulthood a literature review is conducted.

Methods: Data on 6 cases in 2 families are obtained from the available medical records.

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The use of human pluripotent stem cells (hPSCs) in regenerative medicine has great potential. However, it is important to exclude that these cells can undergo malignant transformation, which could lead to the development of malignant tumours. This property of hPSCs is currently being tested using the teratoma assay, through which cells are injected into immunodeficient mice.

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Purpose: Cisplatin is the main systemic treatment modality for male type II germ cell tumors (GCTs). Although generally very effective, 5%-10% of patients suffer from cisplatin-resistant disease. Identification of the driving mechanisms of resistance will enable improved risk stratification and development of alternative treatments.

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The receptor tyrosine kinase MET has gained attention as a therapeutic target. Although MET immunoreactivity is associated with progressive disease, use of targeted therapies has not yet led to major survival benefits. A possible explanation is the lack of companion diagnostics (CDx) that account for proteolytic processing.

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Germ cell tumors (GCTs) are considered to be highly curable; however, there are major differences in the outcomes related to histology and anatomical localization. GCTs originating from the testis are, overall, sensitive to platinum-based chemotherapy, whereas GCTs originating from the mediastinum show a worse response, which remains largely unexplained. Here, we address the differences among GCTs from two different anatomical locations (testicular versus mediastinal/extragonadal), with a specific focus on the role of the P53 pathway.

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Background: Germ cell tumors represent highly curable disease even in metastatic stage. However, poor-risk patients with an unfavorable serum tumor marker (STM) decline after the first cycle of chemotherapy represent a subgroup with dismal prognosis, with approximately 50% cure rate using bleomycin, etoposide, and cisplatin (BEP).

Objective: The aim of this study was to determine the efficacy and safety of paclitaxel, ifosfamide, and cisplatin (TIP) in this patient population.

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The classical serum tumor markers used routinely in the management of testicular germ cell tumor (TGCT) patients-alpha fetoprotein (AFP) and human chorionic gonadotropin (HCG)-show important limitations. miR-371a-3p is the most recent promising biomarker for TGCTs, but it is not sufficiently informative for detection of teratoma, which is therapeutically relevant. We aimed to test the feasibility of hypermethylated () detected in circulating cell-free DNA as a non-invasive diagnostic marker of testicular germ cell tumors, combined with miR-371a-3p.

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MicroRNAs (miRNAs) are short, non-coding RNAs involved in translation regulation. Dysregulation has been identified in cancer cells. miRNAs can be secreted and detectable in body fluids; therefore, they are potential liquid-biopsy biomarkers.

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Background and case: An adolescent male presented with a second mediastinal tumor 1.5 years after treatment of a proven malignant germ-cell tumor in that location. The differential diagnosis included a recurrent germ-cell tumor or a non-germ cell malignancy.

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