Opposing effects of cannabidiol in patient-derived neuroendocrine tumor, pheochromocytoma/paraganglioma primary cultures

CONTEXT

Treatment options for advanced neuroendocrine tumors (NETs), pheochromocytomas and paragangliomas (together PPGLs) are still limited. In recent years, anti-tumor 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 two 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 anti-tumor effects in 5/35 (14%) and significant tumor-promoting effects in 6/35 (17%) of PPGL primary cultures. In terms of anti-tumor effects, cluster 2-related PPGLs showed significantly stronger responsivity to CBD compared to cluster 1-related PPGLs (p = 0.042). Of the cluster 2-related tumors, NF1 PPGLs showed 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 anti-tumor effects in 9/33 of PPGL (27%) and 3/11 of NET (27%) primary cultures, significant tumor-promoting effects in 6/33 of PPGL (18%) and 2/11 of NET (18%) primary cultures.

CONCLUSIONS

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.

Zona Glomerulosa-Derived Klotho Modulates Aldosterone Synthase Expression in Young Female Mice

Klotho plays a critical role in the regulation of ion and fluid homeostasis. A previous study reported that haplo-insufficiency of Klotho in mice results in increased aldosterone synthase (CYP11B2) expression, elevated plasma aldosterone, and high blood pressure. This phenotype was presumed to be the result of diminished Klotho expression in zona glomerulosa (zG) cells of the adrenal cortex; however, systemic effects on adrenal aldosterone production could not be ruled out. To examine whether Klotho expressed in the zG is indeed a critical regulator of aldosterone synthesis, we generated a tamoxifen-inducible, zG-specific mouse model of Klotho deficiency by crossing Klotho-flox mice with Cyp11b2-CreERT mice (zG-Kl-KO). Tamoxifen-treated Cyp11b2-CreERT animals (zG-Cre) served as controls. Rosa26-mTmG reporter mice were used for Cre-dependent lineage-marking. Two weeks after tamoxifen induction, the specificity of the zG-Cre line was verified using immunofluorescence analysis to show that GFP expression was restricted to the zG. RNA in situ hybridization revealed a 65% downregulation of Klotho messenger RNA expression in the zG of zG-Kl-KO female mice at age 12 weeks compared to control mice. Despite this significant decrease, zG-Kl-KO mice exhibited no difference in plasma aldosterone levels. However, adrenal CYP11B2 expression and the CYP11B2 promotor regulatory transcription factors, NGFIB and Nurr1, were enhanced. Together with in vitro experiments, these results suggest that zG-derived Klotho modulates Cyp11b2 but does not evoke a systemic phenotype in young adult mice on a normal diet. Further studies are required to investigate the role of adrenal Klotho on aldosterone synthesis in aged animals.

PLK1 inhibitors as a new targeted treatment for adrenocortical carcinoma

Adrenocortical carcinoma (ACC) is an aggressive malignancy with limited treatment options. Polo-like kinase 1 (PLK1) is a promising drug target; PLK1 inhibitors (PLK1i) have been investigated in solid cancers and are more effective in TP53-mutated cases. We evaluated PLK1 expression in ACC samples and the efficacy of two PLK1i in ACC cell lines with different genetic backgrounds. PLK1 protein expression was investigated by immunohistochemistry in tissue samples and correlated with clinical data. The efficacy of rigosertib (RGS), targeting RAS/PI3K, CDKs and PLKs, and poloxin (Pol), specifically targeting the PLK1 polo-box domain, was tested in TP53-mutated NCI-H295R, MUC-1, and CU-ACC2 cells and in TP53 wild-type CU-ACC1. Effects on proliferation, apoptosis, and viability were determined. PLK1 immunostaining was stronger in TP53-mutated ACC samples vs wild-type (P = 0.0017). High PLK1 expression together with TP53 mutations correlated with shorter progression-free survival (P= 0.041). NCI-H295R showed a time- and dose-dependent reduction in proliferation with both PLK1i (P< 0.05at 100 nM RGS and 30 µM Pol). In MUC-1, a less pronounced decrease was observed (P< 0.05at 1000 nM RGS and 100 µM Pol). 100 nM RGS increased apoptosis in NCI-H295R (P< 0.001), with no effect on MUC-1. CU-ACC2 apoptosis was induced only at high concentrations (P < 0.05 at 3000 nM RGS and 100 µM Pol), while proliferation decreased at 1000 nM RGS and 30 µM Pol. CU-ACC1 proliferation reduced, and apoptosis increased, only at 100 µM Pol. TP53-mutated ACC cell lines demonstrated better response to PLK1i than wild-type CU-ACC1. These data suggest PLK1i may be a promising targeted treatment of a subset of ACC patients, pre-selected according to tumour genetic signature.

Impact of the PI3K-alpha inhibitor alpelisib on everolimus resistance and somatostatin receptor expression in an orthotopic pancreatic NEC xenograft mouse model

The mechanistic target of rapamycin complex 1 (mTORC1) inhibitor everolimus is one of the few approved therapies for locally advanced and metastatic neuroendocrine tumours (NETs). However, after initial disease stabilisation, most patients develop resistance within 1 year. Our aim was to overcome resistance to everolimus by additional treatment with the PI3K-alpha inhibitor alpelisib in an everolimus-resistant orthotopic pancreatic neuroendocrine carcinoma xenograft mouse model. Female SCID mice underwent laparoscopic pancreatic transplantation of everolimus-sensitive (BON1KDMSO) or everolimus-resistant (BON1RR2) NET cells. Both groups were further divided into four treatment groups: placebo, everolimus, alpelisib, and everolimus + alpelisib (combination). Oral treatment was started at a tumour volume of approximately 140 mm3 and continued until 1900-2000 mm3, validated by weekly MRI. Somatostatin receptor expression and tumour viability were analysed by 68Ga-DOTATOC and 18F-FDG PET/CT. Everolimus resistance of the BON1RR2 tumours was confirmed. In the everolimus-sensitive group, everolimus alone, alpelisib alone, and combination treatment significantly prolonged survival, compared to placebo, while in the BON1RR2 group, only combination treatment significantly prolonged survival compared to placebo, but neither everolimus nor alpelisib alone. Placebo-treated everolimus-sensitive tumours grew more rapidly (median survival 45 days), compared to placebo-treated everolimus-resistant tumours (60 days). Within the everolimus-sensitive group, the combination-treated mice showed the longest median survival (52 days). Of all groups, the everolimus-resistant combination-treated group survived longest (69 days). Combination treatment with everolimus and alpelisib seems promising to overcome everolimus resistance in neuroendocrine neoplasms, and should be further examined in a clinical trial.

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.

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.

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.

Three Dimensional Models of Endocrine Organs and Target Tissues Regulated by the Endocrine System

Immortalized cell lines originating from tumors and cultured in monolayers in vitro display consistent behavior and response, and generate reproducible results across laboratories. However, for certain endpoints, these cell lines behave quite differently from the original solid tumors. Thereby, the homogeneity of immortalized cell lines and two-dimensionality of monolayer cultures deters from the development of new therapies and translatability of results to the more complex situation in vivo. Organoids originating from tissue biopsies and spheroids from cell lines mimic the heterogeneous and multidimensional characteristics of tumor cells in 3D structures in vitro. Thus, they have the advantage of recapitulating the more complex tissue architecture of solid tumors. In this review, we discuss recent efforts in basic and preclinical cancer research to establish methods to generate organoids/spheroids and living biobanks from endocrine tissues and target organs under endocrine control while striving to achieve solutions in personalized medicine.

Correction: Sigala et al. A Comprehensive Investigation of Steroidogenic Signaling in Classical and New Experimental Cell Models of Adrenocortical Carcinoma. Cells 2022, 11, 1439

The authors made the following changes to their paper [...].

Transplantation of porcine adrenal spheroids for the treatment of adrenal insufficiency

Primary adrenal insufficiency is a life-threatening disorder, which requires lifelong hormone replacement therapy. Transplantation of xenogeneic adrenal cells is a potential alternative approach for the treatment of adrenal insufficiency. For a successful outcome of this replacement therapy, transplanted cells should provide adequate hormone secretion and respond to adrenal physiological stimuli. Here, we describe the generation and characterization of primary porcine adrenal spheroids capable of replacing the function of adrenal glands in vivo. Cells within the spheroids morphologically resembled adult adrenocortical cells and synthesized and secreted adrenal steroid hormones in a regulated manner. Moreover, the embedding of the spheroids in alginate led to the formation of cellular elongations of steroidogenic cells migrating centripetally towards the inner part of the slab, similar to zona Fasciculata cells in the intact organ. Finally, transplantation of adrenal spheroids in adrenalectomized SCID mice reversed the adrenal insufficiency phenotype, which significantly improved animals' survival. Overall, such adrenal models could be employed for disease modeling and drug testing, and represent the first step toward potential clinical trials in the future.

DNA hypermethylation driven by DNMT1 and DNMT3A favors tumor immune escape contributing to the aggressiveness of adrenocortical carcinoma

BACKGROUND

Adrenocortical carcinoma is rare and aggressive endocrine cancer of the adrenal gland. Within adrenocortical carcinoma, a recently described subtype characterized by a CpG island methylator phenotype (CIMP) has been associated with an especially poor prognosis. However, the drivers of CIMP remain unknown. Furthermore, the functional relation between CIMP and poor clinical outcomes of patients with adrenocortical carcinoma stays elusive.

RESULTS

Here, we show that CIMP in adrenocortical carcinoma is linked to the increased expression of DNA methyltransferases DNMT1 and DNMT3A driven by a gain of gene copy number and cell hyperproliferation. Importantly, we demonstrate that CIMP contributes to tumor aggressiveness by favoring tumor immune escape. This effect could be at least partially reversed by treatment with the demethylating agent 5-azacytidine.

CONCLUSIONS

In sum, our findings suggest that co-treatment with demethylating agents might enhance the efficacy of immunotherapy and could represent a novel therapeutic approach for patients with high CIMP adrenocortical carcinoma.

FSCN1 as a new druggable target in adrenocortical carcinoma

Adrenocortical carcinoma (ACC) is a rare endocrine malignancy with a high risk of relapse and metastatic spread. The actin-bundling protein fascin (FSCN1) is overexpressed in aggressive ACC and represents a reliable prognostic indicator. FSCN1 has been shown to synergize with VAV2, a guanine nucleotide exchange factor for the Rho/Rac GTPase family, to enhance the invasion properties of ACC cancer cells. Based on those results, we investigated the effects of FSCN1 inactivation by CRISPR/Cas9 or pharmacological blockade on the invasive properties of ACC cells, both in vitro and in an in vivo metastatic ACC zebrafish model. Here, we showed that FSCN1 is a transcriptional target for β-catenin in H295R ACC cells and that its inactivation resulted in defects in cell attachment and proliferation. FSCN1 knock-out modulated the expression of genes involved in cytoskeleton dynamics and cell adhesion. When Steroidogenic Factor-1 (SF-1) dosage was upregulated in H295R cells, activating their invasive capacities, FSCN1 knock-out reduced the number of filopodia, lamellipodia/ruffles and focal adhesions, while decreasing cell invasion in Matrigel. Similar effects were produced by the FSCN1 inhibitor G2-044, which also diminished the invasion of other ACC cell lines expressing lower levels of FSCN1 than H295R. In the zebrafish model, metastases formation was significantly reduced in FSCN1 knock-out cells and G2-044 significantly reduced the number of metastases formed by ACC cells. Our results indicate that FSCN1 is a new druggable target for ACC and provide the rationale for future clinical trials with FSCN1 inhibitors in patients with ACC.

Preclinical Evidence of Progesterone as a New Pharmacological Strategy in Human Adrenocortical Carcinoma Cell Lines

Background: Adrenocortical cancer (ACC) is a rare malignancy with a dismal prognosis. The treatment includes mitotane and EDP chemotherapy (etoposide, doxorubicin, and cisplatin). However, new therapeutic approaches for advanced ACC are needed, particularly targeting the metastatic process. Here, we deepen the role of progesterone as a new potential drug for ACC, in line with its antitumoral effect in other cancers. Methods: NCI-H295R, MUC-1, and TVBF-7 cell lines were used and xenografted in zebrafish embryos. Migration and invasion were studied using transwell assays, and MMP2 activity was studied using zymography. Apoptosis and cell cycle were analyzed by flow cytometry. Results: Progesterone significantly reduced xenograft tumor area and metastasis formation in embryos injected with metastatic lines, MUC-1 and TVBF-7. These results were confirmed in vitro, where the reduction of invasion was mediated, at least in part, by the decrease in MMP2 levels. Progesterone exerted a long-lasting effect in metastaticcells. Progesterone caused apoptosis in NCI-H295R and MUC-1, inducing changes in the cell-cycle distribution, while autophagy was predominantly activated in TVBF-7 cells. Conclusion: Our results give support to the role of progesterone in ACC. The involvement of its analog (megestrol acetate) in reducing ACC progression in ACC patients undergoing EDP-M therapy is now under investigation in the PESETA phase II clinical study.

The Vault Complex Is Significantly Involved in Therapeutic Responsiveness of Endocrine Tumors and Linked to Autophagy under Chemotherapeutic Conditions

Cancers display dynamic interactions with their complex microenvironments that influence tumor growth, invasiveness, and immune evasion, thereby also influencing potential resistance to therapeutic treatments. The tumor microenvironment (TME) includes cells of the immune system, the extracellular matrix, blood vessels, and other cell types, such as fibroblasts or adipocytes. Various cell types forming this TME secrete exosomes, and molecules thereby released into the TME have been shown to be important mediators of cellular communication and interplay. Specific stressors in the TME, such as hypoxia, starvation, inflammation, and damage, can furthermore induce autophagy, a fundamental cellular process that degrades and recycles molecules and subcellular components, and recently it has been demonstrated that the small non-coding vault RNA1-1 plays a role as a regulator of autophagy and the coordinated lysosomal expression and regulation (CLEAR) network. Here, we demonstrate for the first time that intra-tumoral damage following effective therapeutic treatment is linked to specific intracellular synthesis and subsequent exosomal release of vault RNAs in endocrine tumors in vitro and in vivo. While we observed a subsequent upregulation of autophagic markers under classical chemotherapeutic conditions, a downregulation of autophagy could be detected under conditions strongly involving inflammatory cascades.

Deoxyguanosine kinase mutation F180S is associated with a lean phenotype in mice

BACKGROUND

Deoxyguanosine kinase (DGUOK) deficiency is one of the genetic causes of mitochondrial DNA depletion syndrome (MDDS) in humans, leading to the hepatocerebral or the isolated hepatic form of MDDS. Mouse models are helpful tools for the improvement of understanding of the pathophysiology of diseases and offer the opportunity to examine new therapeutic options.

METHODS

Herein, we describe the generation and metabolic characterization of a mouse line carrying a homozygous Dguok^F180S/F180S mutation derived from an N-ethyl-N-nitrosourea-mutagenesis screen. Energy expenditure (EE), oxygen consumption (VO₂) and carbon dioxide production (VCO₂) were assessed in metabolic cages. LC-MS/MS was used to quantify plasma adrenal steroids. Plasma insulin and leptin levels were quantified with commercially available assay kits.

RESULTS

Mutant animals displayed significantly lower body weights and reduced inguinal fat pad mass, in comparison to unaffected littermates. Biochemically, they were characterized by significantly lower blood glucose levels, accompanied by significantly lower insulin, total cholesterol, high density lipoprotein and triglyceride levels. They also displayed an almost 2-fold increase in transaminases. Moreover, absolute EE was comparable in mutant and control mice, but EE in mutants was uncoupled from their body weights. Histological examination of inguinal white adipose tissue (WAT) revealed adipocytes with multilocular fat droplets reminiscent of WAT browning. In addition, mRNA and protein expression of Ucp1 was increased. Mutant mice also presented differing mitochondrial DNA content in various tissues and altered metabolic activity in mitochondria, but no further phenotypical or behavioral abnormalities. Preliminary data imply normal survival of Dguok^F180S/F180S mutant animals.

CONCLUSION

Taken together, DGUOK mutation F180S leads to a lean phenotype, with lower glucose, insulin, and lipid levels rendering this mouse model not only useful for the study of MDDS forms but also for deciphering mechanisms resulting in a lean phenotype.

Trabectedin impairs invasiveness and metastasis in adrenocortical carcinoma preclinical models

The pharmacological approach to adrenocortical carcinoma (ACC) is based on mitotane with/without etoposide, doxorubicin, and cisplatin, according to the disease stage. Considering the limited efficacy and toxicity of this treatment, new strategies are required. Trabectedin is a marine-derivated antitumoral agent that inhibits oncogenic transcription. We have already demonstrated trabectedin cytotoxic activity at sub-nanomolar concentrations in ACC cells. Here, we expanded the investigation of trabectedin effect on ACC preclinical models, evaluating whether trabectedin could affect ACC cells' invasiveness and metastasis formation. NCI-H295R, MUC-1, and TVBF-7 cell lines were used. Cell tumor xenografts in Danio rerio embryos were performed. The tumor mass areas and the number of embryos with metastasis were evaluated. The in vitro invasiveness of cells was evaluated. Effects of trabectedin of MMP2, TIMP1, and TIMP2 were evaluated at gene level qRT-PCR. MMP2 secreted in the cell medium was evaluated by Western blot and by zymography. Xenograft experiments demonstrated that trabectedin significantly reduced the tumor area in each ACC cell model and metastasis formation in embryos injected with metastasis-derived cell lines. Trabectedin treatment reduced the invasiveness of ACC cells across the matrix, which was greater at baseline for the metastatic models. In metastatic cell models, protein analysis demonstrated a reduction of MMP2 secretion and activity in the culture medium after treatment. Our results indicate that trabectedin interferes with invasiveness and metastasis processes, both dramatic features of ACC. Furthermore, these results support those previously published in providing the rationale for a clinical evaluation of the efficacy of trabectedin in ACC patients.

Carbonic anhydrases III and IX are new players in the crosstalk between adrenocortical carcinoma and its altered adipose microenvironment

PURPOSE

Adrenocortical carcinoma (ACC), a rare malignancy of the adrenocortex, is characterized by a crosstalk between the adipose microenvironment and tumor. Here, we assessed the involvement of carbonic anhydrase (CA) enzymes III and IX (CAIII and CAIX), in the metabolic alterations of the adipose tissue characterizing obesity and in the local crosstalk between the tumor adipose microenvironment and ACC.

RESULTS/METHODS

CAIII and CAIX expression is altered in visceral adipose tissue (VAT) in obesity and in ACC. A significant CAIX upregulation was present in ACC at advanced stages (n = 14) (fold increase FI = 7.4 ± 0.1, P < 0.05) associated with lower CAIII levels (FI = 0.25 ± 0.06, P < 0.001), compared with lower stages (n = 9). In vitro coculture between visceral adipose stem cells (ASCs) and ACC cell lines, H295R and MUC-1, mimicking the interaction occurring between VAT and advanced ACC, showed a significant CAIX upregulation in H295R but not in MUC-1 cells, and a decreased expression of CAIII. The effect on adipose cells was different when cocultured with H295R or MUC-1 cells. Coculture did not modulate CAIII expression in ASCs, which, however, was significantly downregulated with H295R (FI = 0.34 ± 0.11, P < 0.05) and upregulated by MUC-1 when cocultured ASCs were induced to differentiate toward adipocytes, with an expression profile similar to what found in VAT of obese subjects. CAIX expression was markedly increased in ASCs cocultured with H295R and to a less extent following adipogenesis induction (FI = 150.9 ± 46.5 and FI = 4.6 ± 1.1, P < 0.01, respectively).

CONCLUSION

Our findings highlight a modulation of CAIII and CAIX in the metabolic crosstalk between ACC and its local adipose microenvironment, suggesting that CAs might represent a potential target for novel anticancer therapies.

Tumor suppressor gene ARMC5 controls adrenal redox state through NRF1 turnover

ARMC5

is a tumor suppressor gene frequently mutated in primary bilateral macronodular adrenal hyperplasia (PBMAH), an adrenal cause of Cushing's syndrome. The function of ARMC5 is poorly understood, aside from the fact that it regulates cell viability and adrenal steroidogenesis by mechanisms still unknown. Tumor suppressor genes play an important role in modifying intracellular redox response, which in turn regulates diverse cell signaling pathways. In this study, we demonstrated that inactivation in adrenocortical cells increased the expression of actors scavenging reactive oxygen species, such as superoxide dismutases (SOD) and peroxiredoxins (PRDX) by increasing the transcriptional regulator NRF1. Moreover, ARMC5 is involved in the NRF1 ubiquitination and in its half-life. Finally, inactivation alters adrenocortical steroidogenesis through the activation of p38 pathway and decreases cell sensitivity to ferroptosis participation to increase cell viability. Altogether, this study uncovers a function of ARMC5 as a regulator of redox homeostasis in adrenocortical cells, controlling steroidogenesis and cell survival.

Mitotane Nanocarriers for the Treatment of Adrenocortical Carcinoma: Evaluation of Albumin-Stabilized Nanoparticles and Liposomes in a Preclinical In Vitro Study with 3D Spheroids

Adrenocortical carcinoma (ACC) is a heterogeneous malignancy related to poor prognosis and limited treatment options. The orphan drug mitotane (MT) is still a cornerstone in ACC therapy, however, its application is characterized by low aqueous solubility, poor bioavailability, and unfavorable pharmacokinetics, often resulting in below-target plasma concentrations or toxic side effects. Throughout the last decades, nanoparticulate formulations have become attractive carriers to improve anticancer therapy. In this study, injectable MT liposomes (DOPC-MT) and albumin-stabilized MT nanoparticles (BSA-MT) were investigated in depth with respect to their physicochemical properties, and their colloidal and therapeutical stability upon storage. Furthermore, in vitro cytotoxicity was evaluated using the ACC model cell line NCI-H295R for preparing multicellular tumor spheroids, and was compared to non-malignant human dermal fibroblasts. Our results clearly demonstrate that BSA-MT, unlike DOPC-MT, represents a stable and storable MT formulation with a high drug concentration in an aqueous medium. Dual centrifugation was established as a reproducible method for nanoparticle preparation. Although an efficient cytotoxic effect on ACC tumor spheroids was demonstrated, concomitant low toxicity to fibroblasts suggests that higher drug concentrations may be tolerated in vivo. Consequently, BSA-MT is a novel and promising therapeutical approach to address key challenges in MT treatment.

An update on adrenocortical cell lines of human origin

Adrenocortical carcinoma (ACC) is a rare, heterogenous and highly malignant disease. Management of ACC is dependent on disease stage with complete surgical resection as the only potentially curative option. However, advanced, un-resectable, metastatic stages and also recurrences often require systemic treatments, which are unfortunately nowadays still unsatisfactory. The scarcity of preclinical models reflecting patient heterogeneities and furthermore drug-resistant phenotypes, has hampered the progress and development of new therapies in recent years. In this review, we provide an overview on the classical models and substantial progress which has been made over the last years in context of this aggressive disease.

Mitotane Targets Lipid Droplets to Induce Lipolysis in Adrenocortical Carcinoma

INTRODUCTION

Adrenocortical carcinoma (ACC) is a rare aggressive cancer with low overall survival. Adjuvant mitotane improves survival but is limited by poor response rates and resistance. Mitotane's efficacy is attributed to the accumulation of toxic free cholesterol, predominantly through cholesterol storage inhibition. However, targeting this pathway has proven unsuccessful. We hypothesize that mitotane-induced free-cholesterol accumulation is also mediated through enhanced breakdown of lipid droplets.

METHODOLOGY

ATCC-H295R (mitotane-sensitive) and MUC-1 (mitotane-resistant) ACC cells were evaluated for lipid content using specific BODIPY dyes. Protein expression was evaluated by immunoblotting and flow cytometry. Cell viability was measured by quantifying propidium iodide-positive cells following mitotane treatment and pharmacological inhibitors of lipolysis.

RESULTS

H295R and MUC-1 cells demonstrated similar neutral lipid droplet numbers at baseline. However, evaluation of lipid machinery demonstrated distinct profiles in each model. Analysis of intracellular lipid droplet content showed H295R cells preferentially store cholesteryl esters, whereas MUC-1 cells store triacylglycerol. Decreased lipid droplets were associated with increased lipolysis in H295R and in MUC-1 at toxic mitotane concentrations. Pharmacological inhibition of lipolysis attenuated mitotane-induced toxicity in both models.

CONCLUSION

We highlight that lipid droplet breakdown and activation of lipolysis represent a putative additional mechanism for mitotane-induced cytotoxicity in ACC. Further understanding of cholesterol and lipids in ACC offers potential novel therapeutic exploitation, especially in mitotane-resistant disease.

Adrenal Gland Function and Dysfunction During COVID-19

The coronavirus disease 2019 (COVID-19) pandemic is currently one of the major health concerns worldwide accounting for many deaths and posing a great social and economic burden. Early activation of adrenal hormone secretion is pivotal to surviving systemic microbial infections. In addition, clinical studies demonstrated that glucocorticoids might also be beneficial in reducing disease progression and life deterioration in certain patients with COVID-19. Recent studies demonstrated that SARS-CoV-2 might target the adrenal glands, raising the possibility that at least some COVID-19 complications may be associated with adrenal dysfunction. Whether SARS-CoV-2 infection might cause adrenal dysfunction remains unknown. Histopathological examinations provided evidence that SARS-CoV-2 infection might indeed cause certain structural damage to the adrenal glands, especially concerning its vascular system. However, since no widespread cellular damage to cortical cells was observed, it is less likely that those changes could lead to an immediate adrenal crisis. This assumption is supported by the limited number of studies reporting rather adequate cortisol levels in patients with acute COVID-19. Those studies, however, could not exclude a potential late-onset or milder form of adrenal insufficiency. Although structural damage to adrenal glands is a rarely reported complication of COVID-19, some patients might develop a critical illness-related corticosteroid insufficiency (CIRCI), or iatrogenic adrenal insufficiency resulting from prolonged treatment with synthetic glucocorticoids. In this mini-review article, we aimed at describing and discussing factors involved in the adrenal gland function and possible dysfunction during COVID-19.

Innovative multidimensional models in a high-throughput-format for different cell types of endocrine origin

The adrenal gland provides an important function by integrating neuronal, immune, vascular, metabolic and endocrine signals under a common organ capsule. It is the central organ of the stress response system and has been implicated in numerous stress-related disorders. While for other diseases, regeneration of healthy organ tissue has been aimed at such approaches are lacking for endocrine diseases - with the exception of type-I-diabetes. Moreover, adrenal tumor formation is very common, however, appropriate high-throughput applications reflecting the high heterogeneity and furthermore relevant 3D-structures in vitro are still widely lacking. Recently, we have initiated the development of standardized multidimensional models of a variety of endocrine cell/tissue sources in a new multiwell-format. Firstly, we confirmed common applicability for pancreatic pseudo-islets. Next, we translated applicability for spheroid establishment to adrenocortical cell lines as well as patient material to establish spheroids from malignant, but also benign adrenal tumors. We aimed furthermore at the development of bovine derived healthy adrenal organoids and were able to establish steroidogenic active organoids containing both, cells of cortical and medullary origin. Overall, we hope to open new avenues for basic research, endocrine cancer and adrenal tissue-replacement-therapies as we demonstrate potential for innovative mechanistic insights and personalized medicine in endocrine (tumor)-biology.

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.

A Comprehensive Investigation of Steroidogenic Signaling in Classical and New Experimental Cell Models of Adrenocortical Carcinoma

Adrenocortical carcinoma is a heterogeneous and aggressive cancer that originates from steroidogenic cells within the adrenal cortex. In this study, we have assessed for the preclinical gold standard NCI-H295 in direct comparison with the more recently established MUC-1 and a here newly reported ACC cell line (TVBF-7) the mutational status of important driver genes (TP53, MEN1, PRKAR1A, CTNNB1, APC, ZNRF-3, IGF-2, EGFR, RB1, BRCA1, BRCA2, RET, GNAS and PTEN), Wnt-signaling specificities (CTNNB1 mutation vs. APC mutation vs. wildtype), steroidogenic-(CYP11A1, CYP17A1, HSD3B2, HSD17B4, CYP21A2, CYP11B1, CYP11B2, MC2R, AT1R) and nuclear-receptor-signaling (AR, ER, GCR), varying electrophysiological potentials as well as highly individual hormone secretion profiles (Cortisol, Aldosterone, DHEA, DHEAS, Testosterone, 17-OH Progesterone, among others) which were investigated under basal and stimulated conditions (ACTH, AngII, FSK). Our findings reveal important genetic and pathophysiological characteristics for these three cell lines and reveal the importance of such cell-line panels reflecting differential endocrine functionalities to thereby better reflect clinically well-known ACC patient heterogeneities in preclinical studies.

Sexual dimorphism in COVID-19: potential clinical and public health implications

Current evidence suggests that severity and mortality of COVID-19 is higher in men than in women, whereas women might be at increased risk of COVID-19 reinfection and development of long COVID. Differences between sexes have been observed in other infectious diseases and in the response to vaccines. Sex-specific expression patterns of proteins mediating virus binding and entry, and divergent reactions of the immune and endocrine system, in particular the hypothalamic-pituitary-adrenal axis, in response to acute stress might explain the higher severity of COVID-19 in men. In this Personal View, we discuss how sex hormones, comorbidities, and the sex chromosome complement influence these mechanisms in the context of COVID-19. Due to its role in the severity and progression of SARS-CoV-2 infections, we argue that sexual dimorphism has potential implications for disease treatment, public health measures, and follow-up of patients predisposed to the development of long COVID. We suggest that sex differences could be considered in future pandemic surveillance and treatment of patients with COVID-19 to help to achieve better disease stratification and improved outcomes.

Lack of ZnT8 protects pancreatic islets from hypoxia- and cytokine-induced cell death

Pancreatic β-cells depend on the well-balanced regulation of cytosolic zinc concentrations, providing sufficient zinc ions for the processing and storage of insulin, but avoiding toxic effects. The zinc transporter ZnT8, encoded by SLC30A8,is a key player regarding islet cell zinc homeostasis, and polymorphisms in this gene are associated with altered type 2 diabetes susceptibility in man. The objective of this study was to investigate the role of ZnT8 and zinc in situations of cellular stress as hypoxia or inflammation. Isolated islets of WT and global ZnT8-/- mice were exposed to hypoxia or cytokines and cell death was measured. To explore the role of changing intracellular Zn2+ concentrations, WT islets were exposed to different zinc concentrations using zinc chloride or the zinc chelator N,N,N',N'-tetrakis(2-pyridinylmethyl)-1,2-ethanediamine (TPEN). Hypoxia or cytokine (TNF-α, IFN-γ, IL1-β) treatment induced islet cell death, but to a lesser extent in islets from ZnT8-/- mice, which were shown to have a reduced zinc content. Similarly, chelation of zinc with TPEN reduced cell death in WT islets treated with hypoxia or cytokines, whereas increased zinc concentrations aggravated the effects of these stressors. This study demonstrates a reduced rate of cell death in islets from ZnT8-/- mice as compared to WT islets when exposed to two distinct cellular stressors, hypoxia or cytotoxic cytokines. This protection from cell death is, in part, mediated by a reduced zinc content in islet cells of ZnT8-/- mice. These findings may be relevant for altered diabetes burden in carriers of risk SLC30A8 alleles in man.

Ribociclib Cytotoxicity Alone or Combined With Progesterone and/or Mitotane in in Vitro Adrenocortical Carcinoma Cells

Mitotane is the only approved drug for treating adrenocortical carcinoma (ACC). The regimen added to mitotane is chemotherapy with etoposide, doxorubicin, and cisplatin. This pharmacological approach, however, has a limited efficacy and significant toxicity. Target-therapy agents represent a new promising approach to cancer therapy. Among these, a preeminent role is played by agents that interfere with cell-cycle progression, such as CDK4/6-inhibitors. Here, we investigate whether ribociclib could induce a cytotoxic effect both in ACC cell line and patient-derived primary cell cultures, alone or in combined settings. Cell viability was determined by 3-(4,5-dimethyl-2-thiazol)-2,5-diphenyl-2H-tetrazolium bromide assay, whereas cell proliferation was evaluated by direct count. Binary combination experiments were performed using Chou and Talalay method. Gene expression was analyzed by quantitative RT-PCR, whereas protein expression was evaluated by immunofluorescence. A double staining assay revealed that ribociclib induced a prevalent apoptotic cell death. Cell-cycle analysis was performed to evaluate the effect of ribociclib treatment on cell-cycle progression in ACC cell models. Our results indicate that ribociclib was cytotoxic and reduced the cell proliferation rate. The effect on cell viability was enhanced when ribociclib was combined with progesterone and/or mitotane. The effect of ribociclib on cell-cycle progression revealed a drug-induced cell accumulation in G2 phase. The positive relationship underlined by our results between ribociclib, progesterone, and mitotane strengthen the clinical potential of this combination.

Investigating the Role of Cholesterol and Lipid Trafficking in Mitotane Resistance in Adrenocortical Carcinoma

Introduction: Adrenocortical Carcinoma (ACC) is a rare aggressive cancer which carries a poor prognosis. Adjuvant mitotane improves survival but is limited by poor response rates and resistance following tumour recurrence. Mitotane’s efficacy has been attributed to intracellular accumulation of toxic free cholesterol (FC) predominantly through inhibition of cholesterol storage through SOAT1. Yet SOAT1 specific inhibitors demonstrate inferior efficacy to mitotane in inducing ACC cell death. We hypothesize that mitotane’s efficacy to induce toxic FC accumulation in ACC cells is also mediated through enhanced breakdown of stored cholesterol within intracellular lipid droplets (LDs). Methodology: ATCC-H295R (mitotane sensitive) and MUC-1 (mitotane resistant) ACC cells were evaluated for neutral lipid content using BODIPY493/503 under baseline and cholesterol loaded conditions using Amnis ImageStream, additionally cells were treated with mitotane (H295R - 20, 40, 50µM; MUC1 - 50, 100, 200µM) for 6hr. Analysis of LDs using CE-BODIPY and FA-BODIPY identified cholesterol ester (CE) and triacylglycerol (TAG)-containing LDs, respectively. Lipid droplet-associated proteins (LDAPs) Perilipin (PLIN) 1–4 and hormone sensitive lipase (HSL) were evaluated using western blotting and PCR. Lipid uptake receptors; SRB1, LDLR, LRP1 and CD36 were measured by flow cytometry. Results: Mitotane treatment, within therapeutic range, decreased staining for LDs significantly in H295R. This was also reflected by decreased expression of LDAPs, PLIN1 and PLIN3. The decrease in H295R LDs was associated with increased activation of HSL (pHSL and LIPE). However, this effect was only evident in MUC-1 at supratherapeutic mitotane (200µM). H295R and MUC-1 demonstrated similar overall LD numbers at baseline and under cholesterol supplementation. Expression of PLIN3 was high in both cell lines, while PLIN1, PLIN2 and PLIN4 demonstrated distinct LD profiles in each. Investigation of LD content showed that H295R preferentially store CEs while MUC-1 store only TAG, irrespective of cholesterol-loading. Mitotane treatment significantly reduces both CE and TAG LDs in H295R and MUC-1. Expression of lipid uptake receptors also demonstrated significant variability between cell lines including SRB1 and LRP1. Conclusion: We highlight that lipolysis through LD breakdown and activation of HSL represents a putative additional mechanism for mitotane induced FC cytotoxicity in ACC. We also demonstrate significant differences in cholesterol handling and LDAPs between mitotane sensitive and mitotane resistant models, in particular, the absence of CE LDs in MUC-1. We therefore propose a mechanism of resistance to mitotane through absent CE storage. Further understanding of cholesterol and lipid handling in ACC offers novel therapeutic exploitation, especially in the setting of mitotane resistant disease.

Cytotoxic Effect of Progesterone, Tamoxifen and Their Combination in Experimental Cell Models of Human Adrenocortical Cancer

Progesterone (Pg) and estrogen (E) receptors (PgRs and ERs) are expressed in normal and neoplastic adrenal cortex, but their role is not fully understood. In literature, Pg demonstrated cytotoxic activity on AdrenoCortical Carcinoma (ACC) cells, while tamoxifen is cytotoxic in NCI-H295R cells. Here, we demonstrated that in ACC cell models, ERs were expressed in NCI-H295R cells with a prevalence of ER-β over the ER-α.Metastasis-derived MUC-1 and ACC115m cells displayed a very weak ER-α/β signal, while PgR cells were expressed, although at low level. Accordingly, these latter were resistant to the SERM tamoxifen and scarcely sensitive to Pg, as we observed a lower potency compared to NCI-H295R cells in cytotoxicity (IC₅₀: MUC-1 cells: 67.58 µM (95%CI: 63.22-73.04), ACC115m cells: 51.76 µM (95%CI: 46.45-57.67) and cell proliferation rate. Exposure of NCI-H295R cells to tamoxifen induced cytotoxicity (IC₅₀: 5.43 µM (95%CI: 5.18-5.69 µM) mainly involving ER-β, as their nuclear localization increased after tamoxifen: Δ A.U. treated vs untreated: 12 h: +27.04% (p < 0.01); 24 h: +36.46% (p < 0.0001). This effect involved the SF-1 protein reduction: Pg: -36.34 ± 9.26%; tamoxifen: -46.25 ± 15.68% (p < 0.01). Finally, in a cohort of 36 ACC samples, immunohistochemistry showed undetectable/low level of ERs, while PgR demonstrated a higher expression. In conclusion, ACC experimental cell models expressed PgR and low levels of ER in line with data obtained in patient tissues, thus limiting the possibility of a clinical approach targeting ER. Interestingly, Pg exerted cytotoxicity also in metastatic ACC cells, although with low potency.

Role of FGF Receptors and Their Pathways in Adrenocortical Tumors and Possible Therapeutic Implications

Adrenocortical carcinoma (ACC) is a rare endocrine malignancy and treatment of advanced disease is challenging. Clinical trials with multi-tyrosine kinase inhibitors in the past have yielded disappointing results. Here, we investigated fibroblast growth factor (FGF) receptors and their pathways in adrenocortical tumors as potential treatment targets. We performed real-time RT-PCR of 93 FGF pathway related genes in a cohort of 39 fresh frozen benign and malignant adrenocortical, 9 non-adrenal tissues and 4 cell lines. The expression of FGF receptors was validated in 166 formalin-fixed paraffin embedded (FFPE) tissues using RNA in situ hybridization (RNAscope) and correlated with clinical data. In malignant compared to benign adrenal tumors, we found significant differences in the expression of 16/94 FGF receptor pathway related genes. Genes involved in tissue differentiation and metastatic spread through epithelial to mesechymal transition were most strongly altered. The therapeutically targetable FGF receptors 1 and 4 were upregulated 4.6- and 6-fold, respectively, in malignant compared to benign adrenocortical tumors, which was confirmed by RNAscope in FFPE samples. High expression of FGFR1 and 4 was significantly associated with worse patient prognosis in univariate analysis. After multivariate adjustment for the known prognostic factors Ki-67 and ENSAT tumor stage, FGFR1 remained significantly associated with recurrence-free survival (HR=6.10, 95%CI: 1.78 - 20.86, p=0.004) and FGFR4 with overall survival (HR=3.23, 95%CI: 1.52 - 6.88, p=0.002). Collectively, our study supports a role of FGF pathways in malignant adrenocortical tumors. Quantification of FGF receptors may enable a stratification of ACC for the use of FGFR inhibitors in future clinical trials.

Liver X receptor inhibition potentiates mitotane-induced adrenotoxicity in ACC

Adrenocortical carcinoma (ACC) is a rare aggressive malignancy with a poor outcome largely due to limited treatment options. Here, we propose a novel therapeutic approach through modulating intracellular free cholesterol via the liver X receptor alpha (LXRα) in combination with current first-line pharmacotherapy, mitotane. H295R and MUC-1 ACC cell lines were pretreated with LXRα inhibitors in combination with mitotane. In H295R, mitotane (20, 40 and 50 µM) induced dose-dependent cell death; however, in MUC-1, this only occurred at a supratherapeutic concentration (200 µM). LXRα inhibition potentiated mitotane-induced cytotoxicity in both cell lines. This was confirmed through use of the CompuSyn model which showed moderate pharmacological synergism and was indicative of apoptotic cell death via an increase in annexinV and cleaved-caspase 3 expression. Inhibition of LXRα was confirmed through downregulation of cholesterol efflux pumps ABCA1 and ABCG1; however, combination treatment with mitotane attenuated this effect. Intracellular free-cholesterol levels were associated with increased cytotoxicity in H295R (r2 = 0.5210) and MUC-1 (r2 = 0.9299) cells. While both cell lines exhibited similar levels of free cholesterol at baseline, H295R were cholesterol ester rich, whereas MUC-1 were cholesterol ester poor. We highlight the importance of LXRα mediated cholesterol metabolism in the management of ACC, drawing attention to its role in the therapeutics of mitotane sensitive tumours. We also demonstrate significant differences in cholesterol storage between mitotane sensitive and resistant disease.

SUN-216 Investigating the Role of the Liver X Receptor in Potentiating Mitotane Therapy in Adrenocortical Carcinoma

Introduction: Adrenocortical Carcinoma is a rare aggressive cancer which carries a poor prognosis. Adjuvant mitotane improves survival but is limited by a narrow therapeutic window and severe adverse effects. Liver X receptors (LXRs), part of the nuclear receptor superfamily are highly expressed in adrenal tissue and mediate transcellular and intracellular cholesterol homeostasis. We hypothesise that LXRα inhibition increases toxic lipid accumulation in adrenocortical cancer cells and potentiates the adrenolytic effect of mitotane. Methodology: ATCC-H295R and MUC1 ACC cells and were pre-treated with the LXRα inverse agonist SR9243 5µM and antagonist GSK2033 5µM followed by mitotane treatment (20, 40, 50μΜ) for 6 hours. Cholesterol-methyl-β-cyclodextrin treatment was carried out 1hr prior to mitotane. H295R cells were transfected with a LXR⍺ dominant negative construct using lipofectamine. Cell death was assessed using annexin/PI staining and proliferation using MTT assay. Free cholesterol (FC) levels were assayed using filipin staining and lipid droplets via BODIPY® and analysed on the Amnis ImageStream® imaging cytometer. Downstream targets ABCA1 and ABCG1 were evaluated by qRT-PCR. Lipid droplet associated proteins PLIN 1-4 and hormone sensitive lipase (HSL) expression were evaluated using western blotting. Results: Downstream reduction of ABCA1 and ABCG1 expression confirmed LXRα blockade. Mitotane effectively induced dose-dependent H295R apoptotic cell death which was potentiated pharmacologically and genetically by LXR⍺ inhibition. In line with these findings, cholesterol-methyl-β-cyclodextrin treatment increased cell death in H295R and MUC1 cells. In addition to inducing cell death, LXR⍺ inhibition decreased proliferation of both cell lines. An increase in FC and a decrease in cholesterol esters was observed following mitotane treatment in H295R cells. This was accompanied by decreased lipid droplet numbers confirmed by lower expression of lipid droplet associated proteins, PLIN1-3. These effects were potentiated when mitotane was combined with LXRα inhibition. We demonstrate increased HSL activity, which was associated with higher SOAT-1 expression and increasing toxic FC accumulation. Investigation of lipid droplet content BODIPY® of both cell lines showed H295R cells preferentially store cholesterol esters and MUC1 cells store triacylglycerides.Conclusion: We propose a mechanism for enhancing mitotane’s efficacy as an adrenolytic through increased free cholesterol via LXR⍺inhibition. Targeting the LXRα, its putative ligands, or associated lipid mediators may present a novel therapeutic approach in the setting of primary and metastatic ACC.

SUN-LB22 PLK1 as a New Treatment Target for Adrenocortical Carcinoma

Background: Adrenocortical carcinoma (ACC) is an aggressive malignancy with limited medical treatment options. We previously identified polo-like kinase 1 (PLK1) as one of most overexpressed genes in ACC; thus PLK1 represents a potential treatment target for this cancer type. Some PLK1 inhibitors are under evaluation in clinical trials for other solid organ malignancies, and seem to be more effective in TP53 mutated tumours. The aim of this study was to evaluate PLK1 protein levels in a large series of ACC and assess the in vitroefficacy of PLK1 inhibitors in two different ACC cell lines. Methods: 104 formalin-fixed paraffin-embedded ACC tissue samples with available genetic data were investigated. Nuclear PLK1 protein expression was evaluated by immunohistochemistry and a semi-quantitative H-score was calculated. PLK1 expression levels were correlated to clinical and histological parameters. Efficacy of PLK1-specific inhibitor Volasertib (0-200 nM) was tested in the standard NCI-H295R ACCcell line, which presents PLK-1 overexpression and a large TP53 deletion, and in the newly established MUC1 cell line, which bears a frameshift mutation in TP53. Cell proliferation was analysed using DNA fluorescence and cell apoptosis by Caspase Glo 3/7 assay. Results: Nuclear PLK1 expression was classified as high in 59% of ACC samples, with a significant difference noted between TP53-mutated (n=24) and wild-type (n=80) cases (87.5 vs 51%, p<0.01). PLK1 levels did not correlate with either progression-free or overall survival. H295R cells showed a significant time- and dose-dependent reduction of cell proliferation compared to vehicle control after 72h of Volasertib treatment (p<0.005 per trend, p=0.01 by 200nM by non-parametric two-way ANOVA). A less pronounced and non-significant trend towards inhibited proliferation was observed in MUC1 cells. Cell apoptosis was significantly higher in the H295R cells treated with 175nM and 200nM Volasertib when compared to control (p<0.05), while there was no significant difference in MUC1 cells. Conclusion:In this pilot study, we propose PLK1 inhibitors as promising candidates for treatment of a subset of ACC patients that may be pre-selected according to the tumour molecular pattern. We plan to extend functional experiments to further PLK1 inhibitors, including additional ACC cell lines with a different molecular profile.

Cytotoxic Effect of Trabectedin In Human Adrenocortical Carcinoma Cell Lines and Primary Cells

Mitotane is the only drug approved for the treatment of adrenocortical carcinoma (ACC). The regimen to be added to mitotane is a chemotherapy including etoposide, doxorubicin, and cisplatin. This pharmacological approach, however, has a limited efficacy and significant toxicity. Evidence indicates that ACC seems to be sensitive to alkylating agents. Trabectedin is an anti-tumor drug that acts as an alkylating agent with a complex mechanism of action. Here, we investigated whether trabectedin could exert a cytotoxic activity in in vitro cell models of ACC. Cell viability was evaluated by MTT assay on ACC cell lines and primary cell cultures. The gene expression was evaluated by q-RT-PCR, while protein expression and localization were studied by Western blot and immunocytochemistry. Combination experiments were performed to evaluate their interaction on ACC cell line viability. Trabectedin demonstrated high cytotoxicity at sub-nanomolar concentrations in ACC cell lines and patient-derived primary cell cultures. The drug was able to reduce /β catenin nuclear localization, although it is unclear whether this effect is involved in the observed cytotoxicity. Trabectedin/mitotane combination exerted a synergic cytotoxic effect in NCI-H295R cells. Trabectedin has antineoplastic activity in ACC cells. The synergistic cytotoxic activity of trabectedin with mitotane provides the rationale for testing this combination in a clinical study.

Targeted Gene Expression Profile Reveals CDK4 as Therapeutic Target for Selected Patients With Adrenocortical Carcinoma

Adrenocortical carcinomas (ACC) are aggressive tumors with a heterogeneous prognosis and limited therapeutic options for advanced stages. This study aims to identify novel drug targets for a personalized treatment in ACC. RNA was isolated from 40 formalin-fixed paraffin-embedded ACC samples. We evaluated gene expression of 84 known cancer drug targets by reverse transcriptase quantitative real time-PCR and calculated fold change using 5 normal adrenal glands as reference (overexpression by fold change >2.0). The most promising candidate cyclin-dependent kinase 4 (CDK4) was investigated at protein level in 104 ACC samples and tested by in vitro experiments in two ACC cell lines (NCI-H295R and MUC1). The most frequently overexpressed genes were TOP2A (100% of cases, median fold change = 16.5), IGF2 (95%, fold change = 52.9), CDK1 (80%, fold change = 6.7), CDK4 (62%, fold change = 2.6), PLK4 (60%, fold change = 2.8), and PLK1 (52%, fold change = 2.3). CDK4 was chosen for functional validation, as it is actionable by approved CDK4/6-inhibitors (e.g., palbociclib). Nuclear immunostaining of CDK4 significantly correlated with mRNA expression (R = 0.52, P < 0.005). We exposed both NCI-H295R and MUC1 cell lines to palbociclib and found a concentration- and time-dependent reduction of cell viability, which was more pronounced in the NCI-H295R cells in line with higher CDK4 expression. Furthermore, we tested palbociclib in combination with insulin-like growth factor 1/insulin receptor inhibitor linsitinib showing an additive effect. In conclusion, we demonstrate that RNA profiling is useful to discover potential drug targets and that CDK4/6 inhibitors are promising candidates for treatment of selected patients with ACC.

In vitro cytotoxicity of cabazitaxel in adrenocortical carcinoma cell lines and human adrenocortical carcinoma primary cell cultures☆

Adrenocortical cancer (ACC) is a rare and aggressive malignancy with a poor prognosis. The overall 5-year survival rate of patients with ENS@T stage IV ACC is less than 15%. Systemic antineoplastic therapies have a limited efficacy and new drugs are urgently needed. Human ACC primary cultures and cell lines were used to assess the cytotoxic effect of cabazitaxel, and the role of P-glycoprotein in mediating this effect. Cabazitaxel reduced ACC cell viability, both in ACC cell lines and in ACC primary cell cultures. Molecular and pharmacological targeting of ABCB1/P-gp did not modify its cytotoxic effect in NCI-H295R cells, while it increased the paclitaxel-induced toxicity. Cabazitaxel modified the expression of proteins involved in cellular physiology, such as apoptosis and cell cycle regulation. The drug combination cabazitaxel/mitotane exerted an additive/moderate synergism in different ACC cell experimental models. These results provide a rationale for testing cabazitaxel in a clinical study.

Heat Shock Protein 90 as a Prognostic Marker and Therapeutic Target for Adrenocortical Carcinoma

Background: Adrenocortical carcinoma (ACC) is a rare tumor entity with restricted therapeutic opportunities. HSP90 (Heat Shock Protein 90) chaperone activity is fundamental for cell survival and contributes to different oncogenic signaling pathways. Indeed, agents targeting HSP90 function have shown therapeutic efficacy in several cancer types. We have examined the expression of HSP90 in different adrenal tumors and evaluated the use of HSP90 inhibitors in vitro as possible therapy for ACC. Methods: Immunohistochemical expression of HSP90 isoforms was investigated in different adrenocortical tumors and associated with clinical features. Additionally, a panel of N-terminal (17-allylamino-17-demethoxygeldanamycin (17-AAG), luminespib, and ganetespib) and C-terminal (novobiocin and silibinin) HSP90 inhibitors were tested on various ACC cell lines. Results: Within adrenocortical tumors, ACC samples exhibited the highest expression of HSP90β. Within a cohort of ACC patients, HSP90β expression levels were inversely correlated with recurrence-free and overall survival. In functional assays, among five different compounds tested luminespib and ganetespib induced a significant decrease in cell viability in single as well as in combined treatments with compounds of the clinically used EDP-M scheme (etoposide, doxorubicin, cisplatin, mitotane). Inhibition of cell viability correlated furthermore with a decrease in proliferation, in cell migration and an increase in apoptosis. Moreover, analysis of cancer pathways indicated a modulation of the ERK1/2-and AKT-pathways by luminespib and ganetespib treatment. Conclusions: Our findings emphasize HSP90 as a marker with prognostic impact and promising target with N-terminal HSP90 inhibitors as drugs with potential therapeutic efficacy toward ACC.

Targeting the multidrug transporter Patched potentiates chemotherapy efficiency on adrenocortical carcinoma in vitro and in vivo

One of the crucial challenges in the clinical management of cancer is the resistance to chemotherapeutics. We recently demonstrated that the Hedgehog receptor Patched, which is overexpressed in many recurrent and metastatic cancers, is a multidrug transporter for chemotherapeutic agents such as doxorubicin. The present work provides evidences that Patched is expressed in adrenocortical carcinoma (ACC) patients, and is a major player of the doxorubicin efflux and the doxorubicin resistance in the human ACC cell line H295R. We discovered that methiothepin inhibits the doxorubicin efflux activity of Patched. This drug-like molecule enhances the cytotoxic, pro-apoptotic, antiproliferative and anticlonogenic effects of doxorubicin on ACC cells which endogenously overexpress Patched, and thereby mitigates the resistance of these cancer cells to doxorubicin. Moreover, we report that in mice the combination of methiothepin with doxorubicin prevents the development of xenografted ACC tumors more efficiently than doxorubicin alone by enhancing the accumulation of doxorubicin specifically in tumors without obvious undesirable side effects. Our results suggest that the use of an inhibitor of Patched drug efflux such as methiothepin in combination with doxorubicin could be a promising therapeutic option for adrenocortical carcinoma, and most likely also for other Patched-expressing cancers.

Targeting heterogeneity of adrenocortical carcinoma: Evaluation and extension of preclinical tumor models to improve clinical translation

In recent years it has been recognized that clinical translation of novel therapeutic strategies for patients with adrenocortical carcinoma (ACC) often fails. These disappointing results indicate that the currently utilized tumor models only poorly reflect relevant pathophysiology and, thereby, do not predict clinical applicability of novel pharmacological approaches. However, also the development of new preclinical ACC models has remained a challenge with only one human cell line (NCI-H295R) and one recently established human pediatric xenograft model (SJ-ACC3) being available for this highly heterogeneous malignancy. Our current study furthermore reveals a poor reproducibility of therapeutic action between different clones of the most commonly used tumor model NCI-H295R. In an attempt to broaden the current preclinical armamentarium, we aimed at the development of patient-individual tumor models. During these studies, one xenograft (MUC-1) displayed marked engraftment and sustained tumor growth. MUC-1 tumor analysis revealed highly vascularized, proliferating and SF-1 positive xenografts. In a next step, we characterized all currently available human tumor models for ACC for Ki67, SF-1 and EGF-receptor status in comparison with MUC-1-xenografts. In addition, we established a primary culture, which is now viable over 31 passages with sustained nuclear SF-1 and cytoplasmic 3βHSD immuno-positivity. Subsequent investigation of therapeutic responsiveness upon treatment with the current systemic gold standard EDP-M (etoposide, doxorubicin, cisplatin and mitotane) demonstrated maintenance of the clinically observed drug resistance for MUC-1 exclusively. In summary, we provide evidence for a novel patient-derived tumor model with the potential to improve clinical prediction of novel therapeutic strategies for patients with ACC.

Genetic characterization of a mouse line with primary aldosteronism

In an attempt to define novel genetic loci involved in the pathophysiology of primary aldosteronism, a mutagenesis screen after treatment with the alkylating agent N-ethyl-N-nitrosourea was established for the parameter aldosterone. One of the generated mouse lines with hyperaldosteronism was phenotypically and genetically characterized. This mouse line had high aldosterone levels but normal creatinine and urea values. The steroidogenic enzyme expression levels in the adrenal gland did not differ significantly among phenotypically affected and unaffected mice. Upon exome sequencing, point mutations were identified in seven candidate genes (Sspo, Dguok, Hoxaas2, Clstn3, Atm, Tipin and Mapk6). Subsequently, animals were stratified into wild-type and mutated groups according to their genotype for each of these candidate genes. A correlation of their genotypes with the respective aldosterone, aldosterone-to-renin ratio (ARR), urea and creatinine values as well as steroidogenic enzyme expression levels was performed. Aldosterone values were significantly higher in animals carrying mutations in four different genes (Sspo, Dguok, Hoxaas2 and Clstn3) and associated statistically significant adrenal Cyp11b2 overexpression as well as increased ARR was present only in mice with Sspo mutation. In contrast, mutations of the remaining candidate genes (Atm, Tipin and Mapk6) were associated with lower aldosterone values and lower Hsd3b6 expression levels. In summary, these data demonstrate association between the genes Sspo, Dguok, Hoxaas2 and Clstn3 and hyperaldosteronism. Final proofs for the causative nature of the mutations have to come from knock-out and knock-in experiments.

Liposomal doxorubicin for active targeting: surface modification of the nanocarrier evaluated in vitro and in vivo: challenges and prospects

Due to the inability of classical chemotherapeutic agents to exclusively target tumor cells, these treatments are associated with severe toxicity profiles. Thus, long-circulating liposomes have been developed in the past to enhance accumulation in tumor tissue by passive targeting. Accordingly, commercially available liposomal formulations of sterically stabilized liposomal doxorubicin (Caelyx^®, Doxil^®, Lipodox^®) are associated with improved off-target profiles. However, these preparations are still not capable to selectively bind to target cells. Thus, in an attempt to further optimize existing treatment schemes immunoliposomes have been established to enable active targeting of tumor tissues. Recently, we have provided evidence for therapeutic efficacy of anti-IGF1R-targeted, surface modified doxorubicin loaded liposomes. Our approach involved a technique, which allows specific post-modifications of the liposomal surface by primed antibody-anchor conjugates thereby facilitating personalized approaches of commercially available liposomal drugs. In the current study, post-modification of sterically stabilized liposomal Dox was thoroughly investigated including the influence of different modification techniques (PIT, SPIT, SPIT60), lipid composition (SPC/Chol, HSPC/Chol), and buffers (HBS, SH). As earlier in vivo experiments did not take into account the presence of non-integrated ab-anchor conjugates this was included in the present study. Our experiments provide evidence that post-modification of commercially available liposomal preparations for active targeting is possible. Moreover, lyophilisation represents an applicable method to obtain a storable precursor of surface modifying antibody-anchor conjugates. Thus, these findings open up new approaches in patient individualized targeting of chemotherapeutic therapies.

Preclinical progress and first translational steps for a liposomal chemotherapy protocol against adrenocortical carcinoma

Systemic therapy of adrenocortical carcinoma (ACC) is limited by heterogeneous tumor response and adverse effects. Recently, we demonstrated anti-tumor activity of LEDP-M (etoposide, liposomal doxorubicin, liposomal cisplatin, mitotane), a liposomal variant of EDP-M (etoposide, doxorubicin, cisplatin, mitotane). To improve the therapeutic efficacy and off-target profiles of the clinical gold standard EDP-M, we investigated liposomal EDP-M regimens in different preclinical settings and in a small number of ACC patients with very advanced disease. Short- and long-term experiments were performed on two ACC models (SW-13 and SJ-ACC3) in vivo We evaluated the anti-tumoral effects and off-target profiles of EDP-M, LEDP-M and a novel regimen L(l)EDP-M including liposomal etoposide. Furthermore, the role of plasma microRNA-210 as a therapeutic biomarker and first clinical data were assessed. Classical and liposomal protocols revealed anti-proliferative efficacy against SW-13 (EDP-M P < 0.01; LEDP-M: P < 0.001; L(l)EDP-M: P < 0.001 vs controls), whereas in SJ-ACC3, only EDP-M (P < 0.05 vs controls) was slightly effective. Long-term experiments in SW-13 demonstrated anti-tumor efficacy for all treatment schemes (EDP-M: P < 0.01, LEDP-M: P < 0.05, L(l)EDP-M P < 0.001 vs controls). The analysis of pre-defined criteria leading to study termination revealed significant differences for control (P < 0.0001) and EDP-M (P = 0.003) compared to L(l)EDP-M treatment. Raising its potential for therapy monitoring, we detected elevated levels of circulating microRNA-210 in SW-13 after LEDP-M treatment (P < 0.05). In contrast, no comparable effects were detectable for SJ-ACC3. However, overall histological evaluation demonstrated improved off-target profiles following liposomal regimens. The first clinical data indicate improved tolerability of liposomal EDP-M, thus confirming our results. In summary, liposomal EDP-M regimens represent promising treatment options to improve clinical treatment of ACC.

IGF1-R inhibition and liposomal doxorubicin: Progress in preclinical evaluation for the treatment of adrenocortical carcinoma

Adrenocortical carcinoma (ACC) is a tumor with poor prognosis and limited therapeutic options. Therefore, in addition to multi-chemotherapeutic regimens IGF-1 receptor (IGF-1R) targeting approaches have been evaluated including immunoliposomal (IL) preparations utilizing an IGF-1R inhibiting antibody. In the current study, we extended our experiments by long-term treatment regimens in the classical adrenocortical NCIH295R xenograft model as well as by short-term experiments in two novel xenograft models, which all displayed different levels of IGF-1R and IGF-2 expression. Interestingly, these experiments reveal sub-group dependent differences in therapeutic outcome, reflecting clinical observations and indicate, thus, that implementation of this panel of tumor models might be helpful for clinical translation of novel therapeutic regimens in the future.

TNF alpha signaling is associated with therapeutic responsiveness to vascular disrupting agents in endocrine tumors

ASA404 (Vadimezan) belongs to a class of agents with disrupting properties against tumor vasculature, which is partly mediated by TNFα-signaling. Preclinical and early clinical studies have indicated promising results for ASA404, while extended clinical trials performed poorly. Our aim was to investigate the potential therapeutic applicability of ASA404 against endocrine tumors. Moreover, as the reason for the unpredictable clinical anti-tumor activity of ASA 404 remained uncertain in previous studies, we compared two tumor models of endocrine origin with different responses to ASA404 treatment. Specifically, we determined anti-tumoral effects in preclinical models of neuroendocrine tumors of the gastroenteropancreatic system (BON) and adrenocortical cancer (NCI-H295R) in vitro and in xenograft models in vivo. Upon treatment of tumor bearing mice significant anti-tumoral effects, an increase in TNFα as well as activation of TNFα-specific downstream signaling were evident in the BON tumor model while no comparable effects were detectable for NCI-H295R. We identified TNFAIP3/A20, a key molecule of an inhibitory feedback-loop downstream of TNF-receptor 1, CD40, Toll-like receptors, NOD-like receptors and the interleukin-1 receptor signaling cascades, as overexpressed in the adrenocortical carcinoma tumor model. Subsequent analyses of clinical patient samples confirmed a correlation between tumor TNFAIP3 expression levels and overall survival in patients with ACC. Taken together our findings provide evidence that modulation of TNFα-signaling could be of relevance both for the clinical course of ACC patients and as a marker of treatment response.

Xenograft models for adrenocortical carcinoma

Adrenocortical carcinomas (ACCs) are rare, heterogeneous and very malignant endocrine tumors with a poor prognosis. An important prerequisite to optimize existing therapeutic regimens and to develop novel therapeutic strategies are preclinical disease models. In recent years molecular and genetic profiling of surgical tumor specimen led to the identification of novel interesting markers. However, precise involvement of these markers in tumorigenesis and their functional relevance in therapeutic outcome is still under investigation. Xenograft models are important tools for such functional studies as they bear the potential to mimic the complexity of solid tumors including tumor cells, stroma and blood vessels. Thus, for the successful and safe development of novel therapeutic strategies xenograft models remain to be indispensable experimental tools. Here we provide an overview on currently existing xenograft models for ACC, their tissue origins, establishment, implications as well as limitations.

Adrenal and Ovarian Phenotype of a Tissue-Specific Urocortin 2-Overexpressing Mouse Model

Urocortin 2 (UCN2) is a neuropeptide of the CRH family, involved in homeostatic mechanisms, the stress response, and control of anxiety. To elucidate the effects of UCN2 on steroidogenesis, we developed a mouse model that allows a Cre recombinase-determined conditional overexpression of UCN2 (UCN2-COE). In these mice SF1-Cre-driven overexpression of UCN2 was restricted to the adrenal glands, gonads, and parts of the hypothalamus. UCN2-COE animals of both sexes revealed significantly higher plasma UCN2 levels and significantly higher UCN2 expression levels in the adrenals and ovaries. In contrast, the baseline expression of UCN2 was already high in the testes of control mice with no further increase achievable in UCN2-COE animals. Adrenal steroidogenesis of UCN2-COE animals was investigated under baseline conditions, upon an ACTH stimulation test, and following a restraint stress test. A tendency toward lower expression of steroidogenic enzymes was detectable in UCN2-COE animals of both sexes with slight differences between males and females. A similar reduction in the expression levels of the final steps of ovarian steroidogenesis, accompanied by reduced plasma estradiol levels, was observed in female UCN2-COE animals. Thus, adrenal UCN2 overexpression resulted in down-regulation of adrenal steroidogenesis, suggesting a reduction in the stress response in the mouse (stress coping behavior). Similarly, UCN2 overexpression in the ovaries caused a decrease in steroidogenesis and reduction of follicles that had undergone ovulation. Nevertheless, this finding was not associated with reduced fertility.