Reut Halperin

Background: Pheochromocytomas and paragangliomas (PPGLs) can be metastatic in up to 30% of cases. To assess this risk, scoring systems like PASS and GAPP were developed, yet it is unclear whether these scores correlate with somatic genetic alterations. Methods: A retrospective pilot study. Twenty patients with sporadic pheochromocytoma, stratified into high- and low-risk groups based on GAPP and PASS scores. Somatic variant burden, derived from whole-exome sequencing, and clinical variables were compared between groups. Results: Six patients (30.0%) comprised the high-risk group; all had PASS scores >4 and GAPP scores indicating moderately differentiated PPGLs. Compared with the low-risk group, the high-risk group had larger tumors (4.7 vs. 3.4 cm, p = 0.03) and non-significant association with higher diastolic blood pressure (90 vs. 79 mmHg, p = 0.09), normetanephrine (8.5 vs. 2.3 X upper limit of normal [ULN], p = 0.08), and metanephrine (22.9 vs. 9.25 X ULN, p = 0.09) levels. The high-risk group also demonstrated a higher somatic variant burden, particularly for truncating variants (32 vs. 26, p = 0.04). As a continuous variable, only the GAPP score, not PASS score, showed a significant positive correlation with variant burden, observed for both non-missense (r = 0.57, p = 0.009) and frameshift (r = 0.47, p = 0.04) variants. Conclusions: Higher pathological severity scores are associated with increased rates of severe molecular somatic variants. The stronger link between GAPP score and genetic alteration rates suggests it may better reflect the genomic complexity of sporadic PPGLs.

Purpose: Multiple endocrine neoplasia type 2 (MEN2) is caused by germline pathogenic variants (PVs) in the RET proto-oncogene, leading to medullary thyroid carcinoma (MTC), pheochromocytoma, and primary hyperparathyroidism (PHPT). RET p.Lys666Asn is a rare PV, but its clinical significance remains incompletely understood. The purpose of this study is to expand the clinical understanding of the RET Lys666Asn variant. Methods: Index patients carrying the RET Lys666Asn variant were identified through clinical genetic testing in two referral medical centers. Comprehensive clinical evaluation, biochemical screening, and imaging studies were performed to assess the presence of MTC, pheochromocytoma, and PHPT of the index patients and carrier family members. We performed a literature search on Lys666Asn carriers and their clinical manifestations. Results: Ten individuals from five families were identified as carriers of the RET Lys666Asn variant. The median age at diagnosis was 43.7 years (range 2–75 years). Only one individual presented with pheochromocytoma, diagnosed at age 54. The rate of MTC, pheochromocytoma, and PHPT was 0 (0–0.26), 0.1 (0.01–0.39), and 0 (0–0.26), respectively. In a pooled analysis of cases reported in the literature, MTC, pheochromocytoma, and PHPT rate are 0.42 (0.28–0.57), 0.11 (0.04–0.22), and 0.03 (0–0.12), respectively. MTC had a wide age range at presentation (20–70 years). Conclusion: The RET Lys666Asn variant is associated with lower event rate of MEN2-related tumors compared to classical MEN2 variants, particularly MTC and pheochromocytoma. Despite its rarity, pheochromocytoma cannot be excluded in carriers, underscoring the need for individualized screening protocols based on specific RET variants.

Objective: Pheochromocytoma and paraganglioma (PPGL) have high genetic predisposition rates. In this multicenter study, we aimed to identify risk-modulating factors for disease development and aggressiveness in patients carrying pathogenic variants (PPGLgPV) related to PPGL genes. Methods: Observational prospective study including patients with PPGL, family history of PPGL, or suspected PPGL-related hereditary syndrome. Patients underwent clinical and germline PPGLgPV evaluation. Machine-learning analyses were conducted to predict a patient's risk of carrying PPGLgPV, developing PPGL, and developing metastatic or multifocal disease. Results: Of 221 patients (age 33.5 ± 19.9 years, 45.2% males), 143 (64.7%) patients harbored PPGLgPV, and 91 (41.2%) developed PPGL (46 pheochromocytoma, 45 paraganglioma/both, 29 multifocal/metastatic PPGL). Age at diagnosis of 40 years with a solitary PPGL. Pseudohypoxia (PH)-related PPGLgPV carriers were younger at PPGL diagnosis and had an increased risk of multifocal/metastatic disease. Elevated catecholamine metabolites and PH-related PPGLgPV had 80% PPV for metastatic/multifocal disease, vs high NPV for non-elevated catecholamine metabolites with negative family history (100%) or non-PH gene alterations (91%). Patients with PV found incidentally had a lower PPGL risk compared with carriers screened due to a family member with PPGL (P = .026). Conclusions: Machine learning identified combined clinical and genetic characteristics for predicting hereditary PPGL syndromes, and multifocal/metastatic PPGL. This enables personalized risk stratification to guide genetic testing and surveillance in patients with PPGL and their relatives.

Purpose To assess risk factors for peptide receptor radionuclide therapy (PRRT)-related toxicity to the kidneys, liver, and bone marrow (BM). Methods This is a retrospective study of patients with advanced, well-differentiated neuroendocrine neoplasms treated with ¹⁷⁷Lu-DOTATATE. Serial blood tests for complete blood count, kidney function, and liver function tests were drawn before and 2–4 weeks after each PRRT cycle. Toxicity was defined based on the Common Terminology Criteria for Adverse Events (CTCAE). Patients’ parameters were compared to assess the risk of PRRT-related toxicities; correlation analysis between baseline, post-cycle parameters, and their ratios was performed. Multivariable analysis was performed to identify independent predictors for PRRT toxicity. Results In 178 PRRT cycles in 47 patients (53.2% women, median age 65 years), eight patients had hematological toxicity grade ≥ 2 and seven had hepatic toxicity. A positive correlation was found between baseline and post-treatment BM, kidney, and liver markers. Similarly, a positive correlation was found between the post-treatment-to-pre-treatment marker ratio in the first cycle and the full-treatment-to-baseline ratio. Women had a more pronounced decrease in blood WBC count (last/1st measurement ratio, 0.52 ± 0.17 vs. 0.72 ± 0.19, p < 0.001, women vs. men, respectively), with a similar trend for hemoglobin (Hb) concentration (0.97 ± 0.08 vs. 1.01 ± 0.10, p = 0.090) during treatment. In the logistic regression, women’s risk for neutrophil impairment was 8.7 times higher than men’s (p = 0.034). Conclusion Baseline assessment reflects the patient’s reserves and their post-PRRT state. Further, women are more prone to BM-related toxicity from PRRT. These insights can help optimize treatment strategies and improve patient outcomes in this population.

Neuroendocrine tumors (NETs) occur primarily in the small intestine, lung, and pancreas. Due to their rarity compared to other malignancies in these organs, their complex biology remains poorly understood, including their oncogenesis, tumor composition, and the intriguing phenomena of mixed neuroendocrine non-neuroendocrine neoplasms (MiNEN). Here, we profiled ten low-grade small intestine NET (SiNET) samples as well as one mixed lung tumor by single-cell or single-nuclei RNA-seq. We find that SiNETs are largely separated into two distinct subtypes, in which the neuroendocrine cells upregulate epithelial or neuronal markers, respectively. Surprisingly, in both subtypes, the neuroendocrine cells are largely non-proliferative while higher proliferation is observed in multiple non-malignant cell types. Specifically, B and plasma cells are highly proliferative in the epithelial-like SiNET subtype, potentially reflecting the outcome of high Migration Inhibitory Factor (MIF) expression in those tumors, which may constitute a relevant target. Finally, our analysis of a mixed lung neuroendocrine tumor identifies a population of putative progenitor cells that may give rise to both neuroendocrine and non-neuroendocrine (squamous) cells, potentially explaining the origin of the mixed histology. Taken together, our results provide important insights and hypotheses regarding the biology of neuroendocrine neoplasms.

PURPOSE: Patients with advanced, well-differentiated neuroendocrine tumors (WD-NETs) often require both peptide receptor radionuclide therapy (PRRT) and subsequent chemotherapy. However, no mid-PRRT predictors are available to identify patients who will not benefit from subsequent PRRT to limit their radiation exposure. Our aim is to characterize patients for whom subsequent PRRT is less efficacious on the basis of mid-PRRT evaluation. MATERIALS AND METHODS: A retrospective study of patients with WD-NET who underwent ≥four PRRT cycles. Data gathered included demographics, tumor grade, stage, and response (partial response [PR], stable disease [SD], and progressive disease [PD]) on the basis of RECIST 1.1 criteria and ⁶⁸ Ga-dotatate positron emission tomography-computerized tomography pretreatment, after second and fourth treatment cycle, 6 months after fourth cycle, and at last follow-up. RESULTS: Fifty-one patients (51.6% women; age at diagnosis 66.0 ± 1.65 years), with pancreatic NET (PNET; n = 24), small intestine NET (n = 13), or other NET (n = 14), received PRRT, resulting in PR (n = 21), SD (n = 23), and PD (n = 3). Of the patients reaching PR after PRRT, most reached PR after two treatments (70.4%), with only 11.8% PR occurring between subsequent cycles ( P = .001). Furthermore, patients with PR at mid-treatment had higher PR rates after PRRT completion than those with SD ( P = .007). Patients harboring PNET who achieved PR had a more pronounced reduction of tumor burden in additional cycles than patients who did not (25.6% v 1.5%; P = .03, respectively). On the multivariable model, adjusted for grade and primary site, PR at mid-treatment evaluation was associated with a 20.9 adjusted odds ratio for additional PR at PRRT completion ( P = .002). CONCLUSION: Mid-PRRT assessment predicts subsequent PRRT response in patients with WD-NET, especially those with PNET, informing personalized management and consideration of reduced bone marrow radiation exposure in high-risk patients.

Introduction: Pheochromocytomas and paragangliomas (PPGLs) typically secrete catecholamines and their metabolites (metanephrines [MN] and normetanephrine [NMN]). Catecholamines are synthesized by several enzymes: phenylalanine hydroxylase (encoded by PAH), tyrosine hydroxylase (TH), aromatic L‐amino acid decarboxylase (DDC), dopamine β‐hydroxylase (DBH), and phenylethanolamine N‐methyltransferase (PNMT). MN/NMN secretion varies between anatomical and molecular subgroups. The aim of this study was to assess the correlation between DNA methylation of catecholamine synthesis genes and MN/NMN secretion.Methods: Gene promoter methylation of PAH, TH, AADC, DBH, and PNMT were extracted and calculated based on publicly available data. Comparisons and correlation analysis were performed between MN ± NMN (MN/NMN), NMN only, and neither/unknown secretion patterns. Methylation levels and MN/NMN patterns were compared by three genetic alteration subgroups: pseudohypoxia (PH), kinase signaling (KS), and others.Results: A total of 178 cases were included. Methylation of PAH CpGs negatively correlated with probability for MN/NMN secretion (p < .05 for all CpGs) and positively with NMN‐only secretion. NMN‐only secreting tumors had significantly higher promoter methylation of PAH, DBH, and PNMT compared with MN/NMN‐secreting tumors. MN/NMN‐secreting PPGLs had mainly KS alterations (52.1%), whereas NMN‐only PPGLs had PH alterations (41.9%). PPGLs in the PH versus KS group had gene promoter hypermethylation of PAH (p = .002), DBH (p = .02), and PNMT (p = .003).Conclusions: Promoter methylation of genes encoding catecholamine synthesis enzymes is strongly and inversely correlated with MN/NMN patterns in PPGLs. KS and PH‐related tumors have distinct methylation patterns. These results imply that methylation is a key regulatory mechanism of catecholamine synthesis in PPGLs.

The catecholaldehyde hypothesis for the pathogenesis of Parkinson’s disease centers on accumulation of 3,4-dihydroxyphenylacetaldehyde (DOPAL) in dopaminergic neurons. To test the hypothesis, it is necessary to reduce DOPAL and assess if this improves locomotor abnormalities. Systemic administration of rotenone to rats reproduces the motor and central neurochemical abnormalities characterizing Parkinson’s disease. In this study, we used the monoamine oxidase inhibitor (MAOI) deprenyl to decrease DOPAL production, with or without the antioxidant N-acetylcysteine (NAC). Adult rats received subcutaneous vehicle, rotenone (2 mg/kg/day via a minipump), or rotenone with deprenyl (5 mg/kg/day i.p.) with or without oral NAC (1 mg/kg/day) for 28 days. Motor function tests included measures of open field activity and rearing. Striatal tissue was assayed for contents of dopamine, DOPAL, and other catechols. Compared to vehicle, rotenone reduced locomotor activity (distance, velocity and rearing); increased tissue DOPAL; and decreased dopamine concentrations and inhibited vesicular sequestration of cytoplasmic dopamine and enzymatic breakdown of cytoplasmic DOPAL by aldehyde dehydrogenase (ALDH), as indicated by DA/DOPAL and DOPAC/DOPAL ratios. The addition of deprenyl to rotenone improved all the locomotor indices, increased dopamine and decreased DOPAL contents, and corrected the rotenone-induced vesicular uptake and ALDH abnormalities. The beneficial effects were augmented when NAC was added to deprenyl. Rotenone evokes locomotor and striatal neurochemical abnormalities found in Parkinson’s disease, including DOPAL buildup. Administration of an MAOI attenuates these abnormalities, and NAC augments the beneficial effects. The results indicate a pathogenic role of DOPAL in the rotenone model and suggest that treatment with MAOI+NAC might be beneficial for Parkinson’s disease treatment.