Midgut neuroendocrine tumor patients have a depleted gut microbiome with a discriminative signature.

RATIONALE: When compared to other types of cancer, the prevalence of midgut neuroendocrine tumors (NET) has disproportionally increased over the past decades. To date, there has been very little progress in discovering (epi)genetic drivers and treatment options for these tumors. Recent microbiome research has revealed that enteroendocrine cells communicate with the intestinal microbiome and has provided novel treatment targets for various other cancer types. Hence, our aim was to analyze the role of the gut microbiome in midgut NET patients. METHODS: Fecal samples, prospectively collected from patients and control subjects, were analyzed with next generation 16S sequencing. Patients with neuroendocrine carcinomas and recent antibiotics use were excluded. Relevant variables were extracted from questionnaires and electronic health records. Microbial composition was compared between patients and controls as well as between groups within the patient cohort. RESULTS: 87 midgut NET patients and 95 controls were included. Midgut NET patients had a less rich and diverse gut microbiome than controls (p < 0.001). Moreover, we identified 31 differentially abundant species and a gut microbial signature consisting of 17 species that was predictive of midgut NET presence with an area under the receiver operating characteristic curve of 0.863. Gut microbial composition was not directly associated with the presence of the carcinoid syndrome, tumor grade or multifocality. Nonetheless, we did observe a potential link between microbial diversity and the presence of carcinoid syndrome symptoms within the subset of patients with elevated 5-hydroxyindolacetic acid levels. CONCLUSION: Midgut NET patients have an altered gut microbiome which suggests a role in NET development and could provide novel targets for microbiome-based diagnostics and therapeutics.

Unfavorable biological behavior and treatment response of neuroendocrine ovarian metastases of midgut neuroendocrine tumors.

Neuroendocrine ovarian metastases (NOM) predominantly derive from midgut neuroendocrine tumors (NETs) and develop in about 25% of women with advanced stage of this malignancy. Little is known of the growth rate and treatment response of NOM. We therefore evaluated the efficacy of different management options for patients with NOM, including peptide receptor radionuclide therapy (PRRT), somatostatin analogues (SSAs) and oophorectomy. Records were screened for patients with well-differentiated NOM of midgut origin that presented in our NET referral center between 1991 and 2022. Progression-free survival (PFS) and tumor growth rate (TGR) of ovarian and extra-ovarian metastases were determined using RECIST (response evaluation criteria in solid tumors) 1.1. In 12 available patients undergoing PRRT, NOM were associated with a shorter PFS than extra-ovarian metastases (P = 0.003). While PRRT induced a similar decrease in TGR for ovarian and extra-ovarian lesions in nine patients with available data (-2.3 vs -1.4, P > 0.05), only the TGR of NOM remained positive after PRRT. In 16 patients treated with SSAs, the TGR of NOM was almost three times that of extra-ovarian lesions during treatment (2.2 vs 0.8, P = 0.011). Oophorectomy was performed in 46 of the 61 included patients and was significantly associated with a prolonged OS (115 vs 38 months, P < 0.001). This association persisted after propensity score matching and correction for tumor grade and simultaneous tumor debulking. In conclusion, NOM have a higher TGR compared to extra-ovarian metastases, resulting in a shorter PFS after PRRT. Bilateral salpingo-oophorectomy should be considered for postmenopausal women with NOM undergoing surgery for metastatic midgut NETs.

Strategies Towards Improving Clinical Outcomes of Peptide Receptor Radionuclide Therapy.

PURPOSE OF REVIEW: Peptide receptor radionuclide therapy (PRRT) with [177Lu-DOTA0,Tyr3] octreotate is an effective and safe second- or third-line treatment option for patients with low-grade advanced gastroenteropancreatic (GEP) neuroendocrine neoplasms (NEN). In this review, we will focus on possible extensions of the current use of PRRT and on new approaches which could further improve its treatment efficacy and safety. RECENT FINDINGS: Promising results were published regarding PRRT in other NENs, including lung NENs or high-grade NENs, and applying PRRT as neoadjuvant or salvage therapy. Furthermore, a diversity of strategic approaches, including dosimetry, somatostatin receptor antagonists, somatostatin receptor upregulation, radiosensitization, different radionuclides, albumin binding, alternative renal protection, and liver-directed therapy in combination with PRRT, have the potential to improve the outcome of PRRT. Also, novel biomarkers are presented that could predict response to PRRT. Multiple preclinical and early clinical studies have shown encouraging potential to advance the clinical outcome of PRRT in NEN patients. However, at this moment, most of these strategies have not yet reached the clinical setting of randomized phase III trials.

The role of AIP variants in pituitary adenomas and concomitant thyroid carcinomas in the Netherlands: a nationwide pathology registry (PALGA) study.

PURPOSE: Germline mutations in the aryl-hydrocarbon receptor interacting protein (AIP) have been identified often in the setting of familial isolated pituitary adenoma (FIPA). To date there is no strong evidence linking germline AIP mutations to other neoplasms apart from the pituitary. Our primary objective was to investigate the prevalence of AIP gene mutations and mutations in genes that have been associated with neuroendocrine tumors in series of tumors from patients presenting with both pituitary adenomas and differentiated thyroid carcinomas (DTCs). METHODS: Pathology samples were retrieved from all pituitary adenomas in patients with concomitant DTCs, including one with a known germline AIP variant. Subsequently, two additional patients with known germline AIP variants were included, of which one presented only with a follicular thyroid carcinoma (FTC). RESULTS: In total, 17 patients (14 DTCs and 15 pituitary adenomas) were investigated by targeted next generation sequencing (NGS). The pituitary tumor samples revealed no mutations, while among the thyroid tumor samples BRAF (6/14, 42.9%) was the most frequently mutated gene, followed by NRAS (3/11, 27.3%). In one AIP-mutated FIPA kindred, the AIP-variant c.853C>T; p.Q285* was confirmed in the FTC specimen, including evidence of loss of heterozygosity (LOH) at the AIP locus in the tumor DNA. CONCLUSION: Although most observed variants in pituitary adenomas and DTCs were similar to those of sporadic DTCs, we confirmed in one AIP mutation-positive case the AIP-variant and LOH at this locus in an FTC specimen, which raises the potential role of the AIP mutation as a rare initiating event.

MDR1 inhibition increases sensitivity to doxorubicin and etoposide in adrenocortical cancer.

Chemotherapy for adrenocortical carcinoma (ACC) has limited efficacy and is accompanied by severe toxicity. This lack of effectiveness has been associated with high tumoral levels of the multidrug resistance (MDR) pump P-glycoprotein (P-gp), encoded by the MDR1 gene. In this study, effects of P-gp inhibition on the sensitivity of ACC cells to cytotoxic drugs were evaluated. MDR1 mRNA and P-gp expression were determined in human adrenal tissues and cell lines. H295R, HAC15 and SW13 cells were treated with mitotane, doxorubicin, etoposide, cisplatin and streptozotocin, with or without the P-gp inhibitors verapamil and tariquidar. Cell growth and surviving fraction of colonies were assessed. MDR1 mRNA and P-gp protein expression were lower in ACCs than in adrenocortical adenomas (P < 0.0001; P < 0.01, respectively). MDR1 and P-gp expression were positively correlated in ACC (P < 0.0001, ρ = 0.723). Mitotane, doxorubicin, cisplatin and etoposide dose dependently inhibited cell growth in H295R, HAC15 and SW13. Tariquidar, and in H295R also verapamil, increased the response of HAC15 and H295R to doxorubicin (6.3- and 7.5-fold EC50 decrease in H295R, respectively; all P < 0.0001). Sensitivity to etoposide was increased in H295R and HAC15 by verapamil and tariquidar (all P < 0.0001). Findings were confirmed when assessing colony formation. We show that cytotoxic drugs, except streptozotocin, used for ACC treatment, inhibit ACC cell growth and colony formation at clinically achievable concentrations. P-gp inhibition increases sensitivity to doxorubicin and etoposide, suggesting that MDR1 is involved in sensitivity to these drugs and could be a potential target for cytotoxic treatment improvement in ACC.

Hotspot DAXX, PTCH2 and CYFIP2 mutations in pancreatic neuroendocrine neoplasms.

Mutations in DAXX/ATRX, MEN1 and genes involved in the phosphoinositide-3-kinase/Akt/mammalian target of rapamycin (PI3K/Akt/mTOR) pathway have been implicated in pancreatic neuroendocrine neoplasms (pNENs). However, mainly mutations present in the majority of tumor cells have been identified, while proliferation-driving mutations could be present only in small fractions of the tumor. This study aims to identify high- and low-abundance mutations in pNENs using ultra-deep targeted resequencing. Formalin-fixed paraffin-embedded matched tumor-normal tissue of 38 well-differentiated pNENs was sequenced using a HaloPlex targeted resequencing panel. Novel amplicon-based algorithms were used to identify both single nucleotide variants (SNVs) and insertion-deletions (indels) present in >10% of reads (high abundance) and in <10% of reads (low abundance). Found variants were validated by Sanger sequencing. Sequencing resulted in 416,711,794 reads with an average target base coverage of 2663 ± 1476. Across all samples, 32 high-abundance somatic, 3 germline and 30 low-abundance mutations were withheld after filtering and validation. Overall, 92% of high-abundance and 84% of low-abundance mutations were predicted to be protein damaging. Frequently, mutated genes were MEN1, DAXX, ATRX, TSC2, PI3K/Akt/mTOR and MAPK-ERK pathway-related genes. Additionally, recurrent alterations on the same genomic position, so-called hotspot mutations, were found in DAXX, PTCH2 and CYFIP2. This first ultra-deep sequencing study highlighted genetic intra-tumor heterogeneity in pNEN, by the presence of low-abundance mutations. The importance of the ATRX/DAXX pathway was confirmed by the first-ever pNEN-specific protein-damaging hotspot mutation in DAXX. In this study, both novel genes, including the pro-apoptotic CYFIP2 gene and hedgehog signaling PTCH2, and novel pathways, such as the MAPK-ERK pathway, were implicated in pNEN.

Salvage peptide receptor radionuclide therapy with [177Lu-DOTA,Tyr3]octreotate in patients with bronchial and gastroenteropancreatic neuroendocrine tumours.

PURPOSE: Therapy with [177Lu-DOTA,Tyr3]octreotate is effective in patients with grade I/II metastasized and/or inoperable bronchial neuroendocrine tumour (NET) or gastroenteropancreatic NET (GEP-NET). In this study, we investigated the efficacy and safety of salvage treatment with [177Lu-DOTA,Tyr3]octreotate. METHODS: Patients with progressive bronchial NET or GEP-NET were selected for re-(re)treatment if they had benefited from initial peptide receptor radionuclide therapy (I-PRRT) with a minimal progression-free survival (PFS) of 18 months. Patients received an additional cumulative dose of 14.8 GBq of [177Lu-DOTA,Tyr3]octreotate over two cycles per retreatment with PRRT (R-PRRT) or re-retreatment with PRRT (RR-PRRT). RESULTS: The safety and efficacy analyses included 181 patients and 168 patients, respectively, with bronchial NET or GEP-NET. Overall median follow-up was 88.6 months (95% CI 79.0-98.2). Median cumulative doses were 44.7 GBq (range 26.3-46.4 GBq) during R-PRRT (168 patients) and 59.7 GBq (range 55.2-≤60.5 GBq) during RR-PRRT (13 patients). Objective response and stable disease, as best response, were observed in 26 patients (15.5%) and 100 patients (59.5%) following R-PRRT, and in 5 patients (38.5%) and 7 patients (53.8%) following RR-PRRT, respectively. Median PFS was 14.6 months (95% CI 12.4-16.9) following R-PRRT and 14.2 months (95% CI 9.8-18.5) following RR-PRRT. Combined overall survival (OS) after I-PRRT plus R-PRRT and RR-PRRT was 80.8 months (95% CI 66.0-95.6). Grade III/IV bone marrow toxicity occurred in 6.6% and 7.7% of patients after R-PRRT and RR-PRRT, respectively. Salvage therapy resulted in a significantly longer OS in patients with bronchial NET, GEP-NET and midgut NET than in a nonrandomized control group. The total incidence of acute myeloid leukaemia (AML) and myelodysplastic syndrome (MDS) was 2.2%. No PRRT-related grade III/IV nephrotoxicity was observed. CONCLUSION: A cumulative dose of up to 60.5 GBq salvage PRRT with [177Lu-DOTA,Tyr3]octreotate is safe and effective in patients with progressive disease (relapse-PD) following I-PRRT with [177Lu-DOTA,Tyr3]octreotate. Safety appears similar to that of I-PRRT as no higher incidence of AML or MDS was observed. No grade III/IV renal toxicity occurred after retreatment.

DNA methylation profiling in MEN1-related pancreatic neuroendocrine tumors reveals a potential epigenetic target for treatment.

OBJECTIVE: Epigenetic changes contribute to pancreatic neuroendocrine tumor (PanNET) development. Hypermethylation of promoter DNA as a cause of tumor suppressor gene silencing is a well-established oncogenic mechanism that is potentially reversible and therefore an interesting therapeutic target. Multiple endocrine neoplasia type 1 (MEN1) is the most frequent cause of inherited PanNETs. The aim of this study was to determine promoter methylation profiles in MEN1-related PanNETs. DESIGN AND METHODS: Methylation-specific multiplex ligation-dependent probe amplification was used to assess promoter methylation of 56 tumor suppressor genes in MEN1-related (n = 61) and sporadic (n = 34) PanNETs. Differences in cumulative methylation index (CMI), individual methylation percentages and frequency of promoter hypermethylation between subgroups were analyzed. RESULTS: We found promoter methylation of a large number of potential tumor suppressor genes. CMI (median CMI: 912 vs 876, P = 0.207) was the same in MEN1-related and sporadic PanNETs. We found higher methylation percentages of CASP8 in MEN1-related PanNETs (median: 59% vs 16.5%, P = 0.002). In MEN1-related non-functioning PanNETs, the CMI was higher in larger PanNETs (>2 cm) (median: 969.5 vs 838.5; P = 0.021) and in PanNETs with liver metastases (median: 1036 vs 869; P = 0.013). Hypermethylation of MGMT2 was more frequent in non-functioning PanNETs compared to insulinomas (median: 44.7% vs 8.3%; P = 0.022). Hypermethylation of the Von Hippel-Lindau gene promoter was observed in one MEN1-related PanNET and was associated with loss of protein expression. CONCLUSION: Promoter hypermethylation is a frequent event in MEN1-related and sporadic PanNETs. Targeting DNA methylation could be of therapeutic value in MEN1 patients with advanced PanNETs.

Recent developments in the diagnosis and therapy of well-differentiated neuroendocrine tumours.

Well-differentiated neuroendocrine tumours (NETs) of the digestive tract are being increasingly detected, which is partly explained by the increased use of endoscopic and cross-sectional imaging as well as improved recognition at histopathological evaluation. After the discovery of this relatively indolent type of epithelial malignancy over 100 years ago, their sporadic occurrence and divergent biological behaviour at multiple primary sites have hampered dedicated studies into NET pathogenesis and testing of drug efficacy in well-designed clinical trials. The last decade, however, has seen significant improvements in the NET field regarding our understanding of their pathophysiology. This has been substantiated by novel and exciting diagnostic and therapeutic options, including superior positron emission tomography imaging, treatment with unlabelled and radiolabelled somatostatin analogues and inhibitors of the mammalian target of rapamycin and vascular endothelial growth factor pathways. This review summarises contemporary studies within NET patients, which have enriched our clinical repertoire for this disease and have been instrumental in securing a remarkable improvement of overall survival within recent years.

Expression of p27Kip1 and p18Ink4c in human multiple endocrine neoplasia type 1-related pancreatic neuroendocrine tumors.

PURPOSE: Pancreatic neuroendocrine tumors are a major manifestation of multiple endocrine neoplasia type 1 (MEN1). This tumor syndrome is caused by germline mutations in MEN1, encoding menin. Insight into pathogenesis of these tumors might lead to new biomarkers and therapeutic targets for these patients. Several lines of evidence point towards a role for p27Kip1 and p18Ink4c in MEN1-related tumor development in animal models for MEN1, but their contribution to human MEN1-related pancreatic neuroendocrine tumor development is not known. METHODS: In this study, we characterized protein expression of p27Kip1 and p18Ink4c in human MEN1-related PanNETs by immunohistochemistry. From the nationwide DutchMEN1 Study Group database including > 90% of the Dutch MEN1 population, MEN1-patients, who underwent pancreatic surgery, were selected. A tissue micro-array was constructed with available paraffin tissue blocks, and PanNETs from 61 MEN1 patients were eligible for analysis. RESULTS: Expression of p27Kip1 was high in 57 (93%) PanNETs and 67% of the tumors showed low expression of p18Ink4c (67.3%). No association was found between expression of either p27Kip1 or p18Ink4c and clinic-pathological characteristics. CONCLUSIONS: These findings indicate that loss of p18Ink4c, but not p27Kip1, is a common event in the development of MEN1-related PanNETs. Restoration of p18Ink4c function through CDK4/6 inhibitors could be a therapeutic option for MEN1-related PanNETs.

Thyrotoxic periodic paralysis: an unusual presentation of hyperthyroidism.

Thyrotoxic periodic paralysis (TPP) is a complication of hyperthyroidism among Asians, characterised by sudden onset of hypokalaemia and muscle paralysis. Several factors may contribute to a delay in diagnosis, including the subtlety of hyperthyroidism, the transient nature of the events and the rarity of this disease in the West. As life-threatening arrhythmias may occur during an attack, awareness among physicians is necessary for early recognition and treatment. Advances have been made in understanding the pathophysiological mechanism leading to hypokalaemia, which include recently identified mutations of the inwardly rectifying potassium channel Kir2.6. Treatment includes the supplementation of potassium, a nonselective beta-blocker, and ultimately treatment of the underlying hyperthyroidism. Here we report three cases of TPP in the Netherlands, and review the literature on clinical features, pathophysiological hypothesis and treatment.

Clinical benefit of systemic treatment in patients with advanced pancreatic and gastrointestinal neuroendocrine tumours according to ESMO-MCBS and ASCO framework.

Background: Assessment of clinical benefit of systemic treatments of rare diseases including gastroenteropancreatic neuroendocrine tumours (GEP-NET) is challenging. Recently several tools have been developed to grade the clinical benefit of cancer drugs. The European Society for Medical Oncology (ESMO) has developed the ESMO Magnitude of Clinical Benefit Scale (ESMO-MCBS). The American Society of Clinical Oncology (ASCO) has developed and revised the ASCO framework consisting of the Net Health Benefit (NHB) score juxtaposed against the costs of the treatment. In this review, we graded systemic treatments for GEP-NET patients with both frameworks. Methods: The electronic databases (PubMed and EMBASE) were searched for papers reporting comparative trials, conducted in adult GEP-NET patients in the English language. Papers were assessed according to the ESMO-MCBS and the NHB part of the ASCO revised Framework (NHB-ASCO-F) by four independent assessors, and discrepancies were discussed. Results: The search yielded 32 trials of which 6 were eligible for grading with the ESMO-MCBS resulting in scores of 2 or 3. Eight trials were eligible for grading with the NHB-ASCO-F, resulting in scores between 37.6 and 57.4. Trials that were not primary assessable by the tools were analysed separately. Consensus between assessors was reached in 68% of trials with the ESMO-MCBS and in 23% of trials with the NHB-ASCO-F. Conclusion: The currently used systemic treatments for GEP-NET patients had low scores according to the NHB-ASCO-F and none could be graded as meaningful clinical beneficial according to the ESMO-MCBS. Despite the low incidence, the heterogeneous patient population and relatively long natural course of NET, future studies on new treatment modalities should aim for high clinical benefit outcomes.