Insulinoma in childhood: a retrospective review of 22 patients from one referral centre

Background

Insulinomas are very rare in childhood with sparse knowledge on the clinical aspects and the presence of Multiple Endocrine Neoplasia type 1 (MEN1).

Methods

We conducted a retrospective review of patients diagnosed with insulinoma between 1995 and 2021, presenting to one referral centre in Russia. Clinical, biochemical, genetic, imaging and histological data were collected. In addition, follow-up and family data were obtained.

Results

A total of twenty-two children aged 5 to 16 years were identified. The median (range) gap between the first hypoglycaemia symptoms and diagnosis was 10 (1-46) months. Twelve children (55%) were misdiagnosed to have epilepsy and were treated with anticonvulsants before hypoglycemia was revealed. Contrast enhanced MRI and/or CT were accurate to localize the lesion in 82% (n=18). Five patients (23%) had multiple pancreatic lesions. All children underwent surgical treatment. The median (range) diameter of removed tumors was 1.5 (0.3-6) cm. Histopathological studies confirmed the presence of insulinoma in all cases. Immunohistochemical studies revealed G2 differentiation grade in 10 out of 17 cases. Two patients were diagnosed with metastatic insulinoma. One of them had metastases at the time of insulinoma diagnosis, while the other was diagnosed with liver metastases eight years after the surgery. Eight children (36%) were found to carry MEN1 mutations, inherited n=5, de novo n=1, no data, n=2. Children with MEN1 had significantly higher number of pancreatic tumors compared to sporadic cases. All of them developed additional MEN1 symptoms during the following 2-13 years. In the five patients with inherited MEN1, seven family members had hitherto undiscovered MEN1 manifestations.

Conclusions

In this large cohort of children with rare pediatric insulinomas, MEN1 syndrome and G2 tumors were frequent, as well as hitherto undiscovered MEN1 manifestations in family members. Our data emphasize the need of genetic testing in all children with insulinoma and their relatives, even in the absence of any other features, as well as the importance of a prolonged follow-up observation.

Combined Targeting of Pathogenetic Mechanisms in Pancreatic Neuroendocrine Tumors Elicits Synergistic Antitumor Effects

Pancreatic neuroendocrine neoplasms (PanNENs) are the second most common malignancy of the pancreas. Surgery remains the only curative treatment for localized disease. For patients with inoperable advanced or metastatic disease, few targeted therapies are available, but their efficacy is unpredictable and variable. Exploiting prior knowledge on pathogenetic processes involved in PanNEN tumorigenesis, we tested buparlisib (PI3K inhibitor) and ribociclib (CDK4/6 inhibitor), as single agents or in combination, in different preclinical models. First, we used cell lines representative of well-differentiated (INS-1E, NT-3) and poorly differentiated (BON-1) PanNENs. The combination of buparlisib with ribociclib reduced the proliferation of 2D and 3D spheroid cultures more potently than the individual drugs. Buparlisib, but not ribociclib, induced apoptosis. The anti-proliferative activity of the drugs correlated with downstream target inhibition at mRNA and protein levels. We then tested the drugs on primary islet microtissues from a genetic PanNET animal model (Men1-defective mice) and from wild-type mice: the drug combination was effective against the former without altering islet cell physiology. Finally, we treated PanNET patient-derived islet-like 3D tumoroids: the combination of buparlisib with ribociclib was effective in three out of four samples. Combined targeting of PI3K and CDK4/6 is a promising strategy for PanNENs spanning various molecular and histo-pathological features.

Loss of MEN1 function impairs DNA repair capability of pancreatic neuroendocrine tumors

Somatic MEN1 mutations occur in up to 50% of pancreatic neuroendocrine tumors (PanNETs). Clinical studies have shown that radiation therapy (IR) is effective in a subset of PanNETs, but it remains unclear why some patients respond better to IR than others. Herein, we study whether MEN1 loss of function increases radiosensitivity of PanNETs and determine its effect on DNA double-strand break (DSB) repair. After creating a MEN1 knockout PanNET cell line, we confirmed reduced DSB repair capacity in MEN1-deficient cells and linked these findings to a defect in homologous recombination, as well as reduced BRCA2 expression levels. Consistent with this model, we found that MEN1 mutant cells displayed increased sensitivity to the highly trapping poly (ADP-ribose) polymerase (PARP) 1 inhibitor talazoparib in vitro. Our results suggest that combining IR with PARP inhibition may be beneficial in patients with PanNETs and MEN1 loss of function.

Somatic and germline mutations in NETs: Implications for their diagnosis and management

It is now understood that specific somatic and germline mutations may lead to the development of the neuroendocrine tumours (NETs). NETs usually occur as sporadic isolated tumours, although they also may present as part of complex familial endocrine cancer syndromes, such as multiple endocrine neoplasia type 1 (MEN1) and type 2 (MEN2), Von Hippel-Lindau (VHL) and neurofibromatosis syndromes, tuberous sclerosis, Carney triad and dyad, Reed syndrome and polycythaemia-paraganglioma syndromes. Only in MEN2 syndrome is there a specific genotype-phenotype correlation, although in both sporadic and syndromic NETs some gene mutations are associated with specific clinico-pathological features and prognosis. There have been several advances in our understanding of the NETs leading to earlier detection and targeted therapeutic treatment, but given the poor prognosis associated with metastatic NETs, it will be necessary to find new biomarkers for the prediction of malignant potential and to find novel therapeutic targets for NETs.

Pancreatic neuroendocrine tumors: a review

Neuroendocrine tumors (NETs) are a rare and heterogeneous group of tumors with widely varying morphologies and behaviors. Due to their rarity and heterogeneity, progress in improving their treatment has been slow. However, in recent years there have been advances both in their characterization and in the available treatment options. This review will attempt to address these, with particular reference to pancreatic NETs. Pancreatic NETs are a subset of NETs, previously known as islet cell tumors, which appear to be a distinct biological entity, responding differently to systemic treatments compared with NETs arising elsewhere in the GI tract.