Pre-clinical phaeochromocytoma and paraganglioma models: Cell lines, animal models, and a human primary culture model.

While the establishment of human phaeochromocytoma and paraganglioma (PPGL) cell lines has proven to be particularly difficult over several decades of research, there are other reliable pre-clinical PPGL models currently available. This review provides a summary of these models, together with our recently established personalised drug screening platform using patient-derived PPGL primary cultures. Such currently available PPGL models include murine and rat PPGL cell lines, of which only one cell line (PC12) is publicly accessible through a cell repository, and PPGL animal models, of which the patient-derived xenograft models are promising but complex to establish. We have developed next-generation implementation of human PPGL primary cultures, enabling reliable and personalised drug screening and an individualised analysis of tumour drug responsivity based on the tumour's unique genetic, biochemical, immunohistochemical and clinical profile. Overall, reliable PPGL models, including patient-derived primary culture models, are essential to advance pre-clinical research in the field of PPGLs.

Opposing Effects of Cannabidiol in Patient-derived Neuroendocrine Tumor, Pheochromocytoma/Paraganglioma Primary Cultures.

CONTEXT: Treatment options for advanced neuroendocrine tumors (NETs), pheochromocytomas and paragangliomas (PPGLs) are still limited. In recent years, antitumor effects of cannabinoids have been reported; however, there are only very limited data available in NETs or PPGLs. OBJECTIVE: Investigation of the effects of cannabidiol (CBD) on patient-derived human NET/PPGL primary cultures and on NET/PPGL cell lines. METHODS: We established primary cultures derived from 46 different patients with PPGLs (n = 35) or NETs (n = 11) who underwent tumor resection at 2 centers. Treatment of patient primary cultures with clinically relevant doses (5 µM) and slightly higher doses (10 µM) of CBD was performed. RESULTS: We found opposing effects of 5 µM CBD: significant antitumor effects in 5/35 (14%) and significant tumor-promoting effects in 6/35 (17%) of PPGL primary cultures. In terms of antitumor effects, cluster 2-related PPGLs showed significantly stronger responsivity to CBD compared to cluster 1-related PPGLs (P = .042). Of the cluster 2-related tumors, NF1 PPGLs showed the strongest responsivity (4/5 PPGL primary cultures with a significant decrease in cell viability were NF1-mutated). We also found opposing effects of 10 µM CBD in PPGLs and NETs: significant antitumor effects in 9/33 of PPGL (27%) and 3/11 of NET (27%) primary cultures and significant tumor-promoting effects in 6/33 of PPGL (18%) and 2/11 of NET (18%) primary cultures. CONCLUSION: We suggest a potential novel treatment option for some NETs/PPGLs but also provide evidence for caution when applying cannabinoids as supportive therapy for pain or appetite management to cancer patients and possibly as health supplements.

PD-L1 and HIF-2α Upregulation in Head and Neck Paragangliomas after Embolization.

Hypoxia activates pathways associated with tumor progression, metastatic spread, and alterations in the immune microenvironment leading to an immunosuppressive phenotype. In particular, the upregulation of PD-L1, a target for therapy with checkpoint inhibitors, is well-studied in several tumors. However, the relationship between hypoxia and PD-L1 regulation in pheochromocytomas and paragangliomas (PPGL), and especially in paragangliomas treated with embolization, is still largely unexplored. We investigated the expression of the hypoxia-marker HIF-2α and of PD-L1 in a PPGL-cohort with and without embolization as potential biomarkers that may predict the response to treatment with HIF-2α and checkpoint inhibitors. A total of 29 tumor samples from 25 patients who were operated at a single center were included and analyzed utilizing immunohistochemistry (IHC) for PD-L1 and HIF-2α. Embolization prior to surgery was performed in seven (24%) tumors. PD-L1 expression in tumor cells of head and neck paragangliomas (HNPGLs) receiving prior embolization (median PD-L1 positivity: 15%) was significantly higher as compared to PD-L1 expression in HNPGLs without prior embolization (median PD-L1 positivity: 0%) (p = 0.008). Consistently, significantly more HNPGLs with prior embolization were positive for HIF-2α (median nuclear HIF-2α positivity: 40%) as compared to HNPGLs without prior embolization (median nuclear HIF-2α positivity: 0%) (p = 0.016). Our results support the hypothesis that embolization with subsequent hypoxia leads to the upregulation of both PD-L1 and HIF-2α in HNPGLs, and could thus facilitate targeted treatment with HIF-2α and checkpoint inhibitors in the case of inoperable, locally advanced, or metastatic disease.

Prediction of metastatic pheochromocytoma and paraganglioma: a machine learning modelling study using data from a cross-sectional cohort.

BACKGROUND: Pheochromocytomas and paragangliomas have up to a 20% rate of metastatic disease that cannot be reliably predicted. This study prospectively assessed whether the dopamine metabolite, methoxytyramine, might predict metastatic disease, whether predictions might be improved using machine learning models that incorporate other features, and how machine learning-based predictions compare with predictions made by specialists in the field. METHODS: In this machine learning modelling study, we used cross-sectional cohort data from the PMT trial, based in Germany, Poland, and the Netherlands, to prospectively examine the utility of methoxytyramine to predict metastatic disease in 267 patients with pheochromocytoma or paraganglioma and positive biochemical test results at initial screening. Another retrospective dataset of 493 patients with these tumors enrolled under clinical protocols at National Institutes of Health (00-CH-0093) and the Netherlands (PRESCRIPT trial) was used to train and validate machine learning models according to selections of additional features. The best performing machine learning models were then externally validated using data for all patients in the PMT trial. For comparison, 12 specialists provided predictions of metastatic disease using data from the training and external validation datasets. FINDINGS: Prospective predictions indicated that plasma methoxytyramine could identify metastatic disease at sensitivities of 52% and specificities of 85%. The best performing machine learning model was based on an ensemble tree classifier algorithm that used nine features: plasma methoxytyramine, metanephrine, normetanephrine, age, sex, previous history of pheochromocytoma or paraganglioma, location and size of primary tumours, and presence of multifocal disease. This model had an area under the receiver operating characteristic curve of 0·942 (95% CI 0·894-0·969) that was larger (p<0·0001) than that of the best performing specialist before (0·815, 0·778-0·853) and after (0·812, 0·781-0·854) provision of SDHB variant data. Sensitivity for prediction of metastatic disease in the external validation cohort reached 83% at a specificity of 92%. INTERPRETATION: Although methoxytyramine has some utility for prediction of metastatic pheochromocytomas and paragangliomas, sensitivity is limited. Predictive value is considerably enhanced with machine learning models that incorporate our nine recommended features. Our final model provides a preoperative approach to predict metastases in patients with pheochromocytomas and paragangliomas, and thereby guide individualised patient management and follow-up. FUNDING: Deutsche Forschungsgemeinschaft.

Responses to systemic therapy in metastatic pheochromocytoma/paraganglioma: a retrospective multicenter cohort study.

OBJECTIVE: The therapeutic options for metastatic pheochromocytomas/paragangliomas (mPPGLs) include chemotherapy with cyclophosphamide/vincristine/dacarbazine (CVD), temozolomide monotherapy, radionuclide therapies, and tyrosine kinase inhibitors such as sunitinib. The objective of this multicenter retrospective study was to evaluate and compare the responses of mPPGLs including those with pathogenic variants in succinate dehydrogenase subunit B (SDHB), to different systemic treatments. DESIGN: This is a retrospective analysis of treatment responses of mPPGL patients (n = 74) to systemic therapies. METHODS: Patients with mPPGLs treated at 6 specialized national centers were selected based on participation in the ENSAT registry. Survival until detected progression (SDP) and disease-control rates (DCRs) at 3 months were evaluated based on imaging reports. RESULTS: For the group of patients with progressive disease at baseline (83.8% of 74 patients), the DCR with first-line CVD chemotherapy was 75.0% (n = 4, SDP 11 months; SDHB [n = 1]: DCR 100%, SDP 30 months), with somatostatin peptide receptor-based radionuclide therapy (PPRT) 85.7% (n = 21, SDP 17 months; SDHB [n = 10]: DCR 100%, SDP 14 months), with 131I-meta-iodobenzylguanidine (131I-MIBG) 82.6% (n = 23, SDP 43 months; SDHB [n = 4]: DCR 100%, SDP 24 months), with sunitinib 100% (n = 7, SDP 18 months; SDHB [n = 3]: DCR 100%, SDP 18 months), and with somatostatin analogs 100% (n = 4, SDP not reached). The DCR with temozolomide as second-line therapy was 60.0% (n = 5, SDP 10 months; SDHB [n = 4]: DCR 75%, SDP 10 months). CONCLUSIONS: We demonstrate in a real-life clinical setting that all current therapies show reasonable efficacy in preventing disease progression, and this is equally true for patients with germline SDHB mutations.

Hierarchical integration of DNA nanostructures and NanoGold onto a microchip facilitates covalent chemistry-mediated purification of circulating tumor cells in head and neck squamous cell carcinoma.

It is well-established that the combined use of nanostructured substrates and immunoaffinity agents can enhance the cell-capture performance of the substrates, thus offering a practical solution to effectively capture circulating tumor cells (CTCs) in peripheral blood. Developing along this strategy, this study first demonstrated a top-down approach for the fabrication of tetrahedral DNA nanostructure (TDN)-NanoGold substrates through the hierarchical integration of three functional constituents at various length-scales: a macroscale glass slide, sub-microscale self-organized NanoGold, and nanoscale self-assembled TDN. The TDN-NanoGold substrates were then assembled with microfluidic chaotic mixers to give TDN-NanoGold Click Chips. In conjunction with the use of copper (Cu)-catalyzed azide-alkyne cycloaddition (CuAAC)-mediated CTC capture and restriction enzyme-triggered CTC release, TDN-NanoGold Click Chips allow for effective enumeration and purification of CTCs with intact cell morphologies and preserved molecular integrity. To evaluate the clinical utility of TDN-NanoGold Click Chips, we used these devices to isolate and purify CTCs from patients with human papillomavirus (HPV)-positive (+) head and neck squamous cell carcinoma (HNSCC). The purified HPV(+) HNSCC CTCs were then subjected to RT-ddPCR testing, allowing for detection of E6/E7 oncogenes, the characteristic molecular signatures of HPV(+) HNSCC. We found that the resulting HPV(+) HNSCC CTC counts and E6/E7 transcript copy numbers are correlated with the treatment responses in the patients, suggesting the potential clinical utility of TDN-NanoGold Click Chips for non-invasive diagnostic applications of HPV(+) HNSCC.

Metastatic Pheochromocytoma and Paraganglioma: Somatostatin Receptor 2 Expression, Genetics, and Therapeutic Responses.

CONTEXT: Pheochromocytomas and paragangliomas (PPGLs) with pathogenic mutations in the succinate dehydrogenase subunit B (SDHB) are associated with a high metastatic risk. Somatostatin receptor 2 (SSTR2)-dependent imaging is the most sensitive imaging modality for SDHB-related PPGLs, suggesting that SSTR2 expression is a significant cell surface therapeutic biomarker of such tumors. OBJECTIVE: Exploration of the relationship between SSTR2 immunoreactivity and SDHB immunoreactivity, mutational status, and clinical behavior of PPGLs. Evaluation of SSTR-based therapies in metastatic PPGLs. METHODS: Retrospective analysis of a multicenter cohort of PPGLs at 6 specialized Endocrine Tumor Centers in Germany, The Netherlands, and Switzerland. Patients with PPGLs participating in the ENSAT registry were included. Clinical data were extracted from medical records, and immunohistochemistry (IHC) for SDHB and SSTR2 was performed in patients with available tumor tissue. Immunoreactivity of SSTR2 was investigated using Volante scores. The main outcome measure was the association of SSTR2 IHC positivity with genetic and clinical-pathological features of PPGLs. RESULTS: Of 202 patients with PPGLs, 50% were SSTR2 positive. SSTR2 positivity was significantly associated with SDHB- and SDHx-related PPGLs, with the strongest SSTR2 staining intensity in SDHB-related PPGLs (P = .01). Moreover, SSTR2 expression was significantly associated with metastatic disease independent of SDHB/SDHx mutation status (P < .001). In metastatic PPGLs, the disease control rate with first-line SSTR-based radionuclide therapy was 67% (n = 22, n = 11 SDHx), and with first-line "cold" somatostatin analogs 100% (n = 6, n = 3 SDHx). CONCLUSION: SSTR2 expression was independently associated with SDHB/SDHx mutations and metastatic disease. We confirm a high disease control rate of somatostatin receptor-based therapies in metastatic PPGLs.

Targeted Therapies in Pheochromocytoma and Paraganglioma.

Molecular targeted therapy plays an increasingly important role in the treatment of metastatic pheochromocytomas and paragangliomas (PPGLs), which are rare tumors but remain difficult to treat. This mini-review provides an overview of established molecular targeted therapies in present use, and perspectives on those currently under development and evaluation in clinical trials. Recently published research articles, guidelines, and expert views on molecular targeted therapies in PPGLs are systematically reviewed and summarized. Some tyrosine kinase inhibitors (sunitinib, cabozantinib) are already in clinical use with some promising results, but without formal approval for the treatment of PPGLs. Sunitinib is the only therapeutic option which has been investigated in a randomized placebo-controlled clinical trial. It is clinically used as a first-, second-, or third-line therapeutic option for the treatment of progressive metastatic PPGLs. Some other promising molecular targeted therapies (hypoxia-inducible factor 2 alpha [HIF2α] inhibitors, tumor vaccination together with checkpoint inhibitors, antiangiogenic therapies, kinase signaling inhibitors) are under evaluation in clinical trials. The HIF2α inhibitor belzutifan may prove to be particularly interesting for cluster 1B-/VHL/EPAS1-related PPGLs, whereas antiangiogenic therapies seem to be primarily effective in cluster 1A-/SDHx-related PPGLs. Some combination therapies currently being evaluated in clinical trials, such as temozolomide/olaparib, temozolomide/talazoparib, or cabozantinib/atezolizumab, will provide data for novel therapy for metastatic PPGLs. It is likely that advances in such molecular targeted therapies will play an essential role in the future treatment of these tumors, with more personalized therapy options paving the way towards improved therapeutic outcomes.

Personalized drug testing in human pheochromocytoma/paraganglioma primary cultures.

Aggressive pheochromocytomas and paragangliomas (PPGLs) are difficult to treat, and molecular targeting is being increasingly considered, but with variable results. This study investigates established and novel molecular-targeted drugs and chemotherapeutic agents for the treatment of PPGLs in human primary cultures and murine cell line spheroids. In PPGLs from 33 patients, including 7 metastatic PPGLs, we identified germline or somatic driver mutations in 79% of cases, allowing us to assess potential differences in drug responsivity between pseudohypoxia-associated cluster 1-related (n = 10) and kinase signaling-associated cluster 2-related (n = 14) PPGL primary cultures. Single anti-cancer drugs were either more effective in cluster 1 (cabozantinib, selpercatinib, and 5-FU) or similarly effective in both clusters (everolimus, sunitinib, alpelisib, trametinib, niraparib, entinostat, gemcitabine, AR-A014418, and high-dose zoledronic acid). High-dose estrogen and low-dose zoledronic acid were the only single substances more effective in cluster 2. Neither cluster 1- nor cluster 2-related patient primary cultures responded to HIF-2a inhibitors, temozolomide, dabrafenib, or octreotide. We showed particular efficacy of targeted combination treatments (cabozantinib/everolimus, alpelisib/everolimus, alpelisib/trametinib) in both clusters, with higher efficacy of some targeted combinations in cluster 2 and overall synergistic effects (cabozantinib/everolimus, alpelisib/trametinib) or synergistic effects in cluster 2 (alpelisib/everolimus). Cabozantinib/everolimus combination therapy, gemcitabine, and high-dose zoledronic acid appear to be promising treatment options with particularly high efficacy in SDHB-mutant and metastatic tumors. In conclusion, only minor differences regarding drug responsivity were found between cluster 1 and cluster 2: some single anti-cancer drugs were more effective in cluster 1 and some targeted combination treatments were more effective in cluster 2.