Pituitary Dysfunction in Patients with Intracranial Germ Cell Tumors Treated with Radiotherapy

Intracranial germ cell tumors: a view of the endocrinologist

Intracranial germ cell tumors (iGCTs) are rare malignant neoplasms that mainly affect children and adolescents. The incidence, clinical presentation, and prognosis of iGCTs exhibit high heterogeneity. Previous studies have primarily focused on eliminating tumors, reducing tumor recurrence, and improving survival rates, while neglecting the impact of the tumors and their treatment on neuroendocrine function. Throughout the entire course of the disease, neuroendocrine dysfunction may occur and is frequently overlooked by oncologists, neurosurgeons, and radiologists. Endocrinologists, however, are more interested in this issue and have varying priorities at different stages of the disease. From onset to the diagnostic phase, most patients with iGCTs may present with symptoms related to impaired neuroendocrine function, or even experience these symptoms as their first indication of the condition. Particularly, a minority of patients with sellar/suprasellar lesions may exhibit typical imaging features and elevated tumor markers long after the onset of initial symptoms. This can further complicate the diagnosis process. During the peritumor treatment phase, the neuroendocrine function shows dynamic changes and needs to be evaluated dynamically. Once diabetes insipidus and dysfunction of the hypothalamic-pituitary-adrenal and hypothalamic-pituitary-thyroid axes occur, hormone replacement therapy should be administered promptly to ensure successful tumor treatment for the patient. Subsequently, during the long-term management phase after the completion of tumor treatment, the evaluation of growth and development as well as corresponding hormone replacement therapy are the most concerning and complex issues. Thus, this paper reviews the interest of endocrinologists in iGCTs at different stages.

High prevalence of overweight/obesity and dyslipidemia in patients with intracranial germ cell tumors

PURPOSE

To evaluate the prevalence of overweight/obesity and dyslipidemia in patients with intracranial germ cell tumor (iGCT), and to explore the risk factors of it.

METHODS

iGCT patients visiting Peking Union Medical College Hospital between Jan 2008 to Oct 2020 were included. The prevalence of overweight/obesity and dyslipidemia was calculated. Mixed-effects models were used to evaluate the relationship between BMI z-scores, concentration of lipid profiles and potential risk factors.

RESULTS

One hundred and six patients were included. The median follow-up time was 27 (IQR 5-59) months. The number of patients diagnosed with overweight/obesity and dyslipidemia were 49 (46.2%) and 86 (81.1%) during visits. Higher BMI z-scores were associated with treatment (mean difference (MD) 0.51, 95%CI 0.31-0.72), surgical biopsies (MD 0.71, 95%CI 0.16-1.25), adrenal insufficiency (MD 0.37, 95%CI 0.07-0.68), hypothyroidism (MD 0.35, 95%CI 0.06-0.63), glucocorticoid supplementation (MD 0.64, 95%CI 0.40-0.87), and thyroxine supplementation (MD 0.48, 95%CI 0.24-0.72). Hypothalamus involvement was associated with increased TC (MD 0.52, 95%CI 0.06-0.98), TG (MD 0.36, 95%CI 0.01-0.72), LDL-C (MD 0.60, 95%CI 0.20-0.98), and decreased HDL-C (MD - 0.23, 95%CI - 0.44 to - 0.02). Higher TC (MD 0.53, 95%CI 0.26-0.80) and LDL-C (MD 0.39, 95%CI 0.17-0.62) were observed in patients after treatment. Glucocorticoid supplementation was associated with increased TC (MD 0.70, 95%CI 0.38-1.03), LDL-C (MD 0.51, 95%CI 0.24-0.78), and HDL-C (MD 0.25, 95%CI 0.09-0.40), while sex hormone supplementation was associated with decreased TC (MD - 0.74, 95%CI - 1.2 to - 0.29) and TG (MD - 0.47, 95%CI - 0.86 to - 0.08).

CONCLUSION

Overweight/obesity and dyslipidemia were high prevalent in iGCT patients and should be screened during follow-ups.

Panhypopituitarism in a patient with a hypothalamic and pineal germ cell tumor

Summary

Central diabetes insipidus (DI) is characterized by decreased release of antidiuretic hormone, resulting in a variable degree of polyuria. The etiologies are variable, with the vast majority of cases either being idiopathic or resulting from primary or secondary tumors. Such tumors include craniopharyngioma, Langerhans cell histiocytosis, or a variety of inflammatory, vascular, or granulomatous diseases. It is exceptionally rare for pituitary adenomas to present with DI. We describe a young patient who first presented with symptoms consistent with DI. He was tested for DI and found to have panhypopituitarism due to a metastatic pineal germ cell tumor causing thickening of his pituitary stalk.

Learning points

New onset central diabetes insipidus requires dedicated pituitary MRI for determination of etiology. Germ cell tumors in the pineal and suprasellar regions most commonly cause central diabetes insipidus. Determining the etiology of new-onset central diabetes insipidus can radically affect treatment.

MicroRNA-206 relieves irradiation-induced neuroinflammation by regulating connexin 43

Radiation therapy has been widely used for the treatment of various types of cancer; however, it may cause neuroinflammation during the pathological process of the disease. Astrocytes, the most abundant cell type in the central nervous system, have been confirmed to play vital roles in various diseases. Connexin (Cx)43, the main Cx type in astrocytes, which has been identified as a direct target gene of microRNA (miR)-206, was found to be involved in diseases pathologies in regions with astrocytes. The aim of the present study was to investigate the mechanism through which γ-radiation may cause astrocyte neuroinflammation and determine the specific mechanism underlying the effects of miR-206 in irradiation-induced HA-1800 cells. A dual-luciferase reporter system was used to predict and verify the target binding site between Cx43 and miR-206. HA-1800 cell viability and apoptosis were determined using a MTT assay and flow cytometry, respectively. In addition, the HA-1800 cells were induced by γ-radiation, then the protein and mRNA expression levels of Cx43, miR-206 and cleaved-caspase-3 were determined using western blot and reverse transcription-quantitative PCR analyses, respectively. ELISA was also performed to evaluate the concentrations of different inflammatory cytokines (TNF-α, IL-β, IL-6 and IFN-γ). The dual-luciferase reporter system indicated that Cx43 was a direct target of miR-206. miR-206 mimics increased the expression level of miR-206 in the astrocytes. Irradiation suppressed cell proliferation, increased apoptotic cells and enhanced cleaved-caspase-3 expression and inflammatory cytokines secretion in astrocytes. Furthermore, miR-206 was found to be downregulated and its expression was inversely associated with that of Cx43 in γ-radiation-induced astrocytes. Overexpression of miR-206 enhanced miR-206 and suppressed Cx43 expression, while Cx43 was upregulated in HA-1800 cells transfected with miR-206 mimic + Cx43-plasmid. However, the expression level of miR-206 was not significantly different in the Cx43-plasmid transfected group. In addition, it was found that miR-206 mimics relieved irradiation-induced neuroinflammation, which was confirmed by increased cell viability, and reduced cell apoptosis and cleaved caspase-3 protein expression, as well as decreased inflammatory cytokine secretion. Furthermore, all the effects of miR-206 mimics on γ-radiation-induced astrocytes were reversed by Cx43-plasmid. In summary, the results of the present study indicated that miR-206 may relieve irradiation-induced neural damage by regulating Cx43, which may provide a novel research direction and a potential therapeutic target for the clinical treatment of inflammation-associated neuronal injury following irradiation.

Molecular Pathology and Targeted Therapies for Personalized Management of Central Nervous System Germinoma

Intracranial germinomas are rare tumours, usually affecting male paediatric patients. They frequently develop in the pineal and suprasellar regions, causing endocrinological disturbances, visual deficits, and increased intracranial pressure. The diagnosis is established on magnetic resonance imaging (MRI), serum and cerebrospinal fluid (CSF) markers, and tumour stereotactic biopsy. Imaging techniques, such as susceptibility-weighted imaging (SWI), T2* (T2-star) gradient echo (GRE) or arterial spin labelling based perfusion-weighted MRI (ASL-PWI) facilitate the diagnosis. Germinomas are highly radiosensitive tumours, with survival rates >90% in the context of chemoradiotherapy. However, patients with resistant disease have limited therapeutic options and poor survival. The aim of this review is to highlight the genetic, epigenetic, and immunologic features, which could provide the basis for targeted therapy. Intracranial germinomas present genetic and epigenetic alterations (chromosomal aberrations, KIT, MAPK and PI3K pathways mutations, DNA hypomethylation, miRNA dysregulation) that may represent targets for therapy. Tyrosine kinase and mTOR inhibitors warrant further investigation in these cases. Immune markers, PD-1 (programmed cell death protein 1) and PD-L1 (programmed death-ligand 1), are expressed in germinomas, representing potential targets for immune checkpoint inhibitors. Resistant cases should benefit from a personalized management: genetic and immunological testing and enrolment in trials evaluating targeted therapies in intracranial germinomas.