Therapeutic Targets for Adrenocortical Carcinoma in the Genomics Era

Advances in translational research of the rare cancer type adrenocortical carcinoma

Adrenocortical carcinoma is a rare malignancy with an annual worldwide incidence of 1-2 cases per 1 million and a 5-year survival rate of <60%. Although adrenocortical carcinoma is rare, such rare cancers account for approximately one third of patients diagnosed with cancer annually. In the past decade, there have been considerable advances in understanding the molecular basis of adrenocortical carcinoma. The genetic events associated with adrenocortical carcinoma in adults are distinct from those of paediatric cases, which are often associated with germline or somatic TP53 mutations and have a better prognosis. In adult primary adrenocortical carcinoma, the main somatic genetic alterations occur in genes that encode proteins involved in the WNT-β-catenin pathway, cell cycle and p53 apoptosis pathway, chromatin remodelling and telomere maintenance pathway, cAMP-protein kinase A (PKA) pathway or DNA transcription and RNA translation pathways. Recently, integrated molecular studies of adrenocortical carcinomas, which have characterized somatic mutations and the methylome as well as gene and microRNA expression profiles, have led to a molecular classification of these tumours that can predict prognosis and have helped to identify new therapeutic targets. In this Review, we summarize these recent translational research advances in adrenocortical carcinoma, which it is hoped could lead to improved patient diagnosis, treatment and outcome.

The Characteristics of Tumor Microenvironment Predict Survival and Response to Immunotherapy in Adrenocortical Carcinomas

Increasing evidence confirms that tumor microenvironment (TME) can influence tumor progression and treatment, but TME is still understudied in adrenocortical carcinoma (ACC). In this study, we first scored TME using the xCell algorithm, then defined genes associated with TME, and then used consensus unsupervised clustering analysis to construct TME-related subtypes. Meanwhile, weighted gene co-expression network analysis was used to identify modules correlated with TME-related subtypes. Ultimately, the LASSO-Cox approach was used to establish a TME-related signature. The results showed that TME-related scores in ACC may not correlate with clinical features but do promote a better overall survival. Patients were classified into two TME-related subtypes. Subtype 2 had more immune signaling features, higher expression of immune checkpoints and MHC molecules, no CTNNB1 mutations, higher infiltration of macrophages and endothelial cells, lower tumor immune dysfunction and exclusion scores, and higher immunophenoscore, suggesting that subtype 2 may be more sensitive to immunotherapy. 231 modular genes highly relevant to TME-related subtypes were identified, and a 7-gene TME-related signature that independently predicted patient prognosis was established. Our study revealed an integrated role of TME in ACC and helped to identify those patients who really responded to immunotherapy, while providing new strategies on risk management and prognosis prediction.

Vitamin D receptor activation is a feasible therapeutic target to impair adrenocortical tumorigenesis

OBJECTIVE

To evaluate the therapeutic potential of vitamin D receptor (VDR) signaling in adrenocortical carcinoma (ACC) cells.

METHODS

We evaluated VDR's methylation pattern in H295R ACC cells, and investigated the effects of calcitriol and seocalcitol treatments on adrenocortical tumorigenesis.

RESULTS

VDR was hypermethylated and underexpressed in basal H295R cells. Treatments with calcitriol and seocalcitol restored VDR signaling, resulted in antiproliferative effects, and impaired Wnt/B-catenin signaling. RNAseq of treated cells demonstrated VDR activation on steroid hormones biosynthesis and Rap1 signaling, among others. In vivo, seocalcitol constrained the growth of H295R xenografts and reduced autonomous tumor steroid secretion without hypercalcemia-associated side effects.

CONCLUSIONS

H295R cells present VDR hypermethylation, which can be responsible for its underexpression and signaling inactivation under basal conditions. VDR signaling promoted antiproliferative effects in vitro and in vivo, suggesting that it may be a potential therapeutic target for ACC and a valuable tool for patient's clinical management.

Update on Biology and Genomics of Adrenocortical Carcinomas: Rationale for Emerging Therapies

The adrenal glands are paired endocrine organs that produce steroid hormones and catecholamines required for life. Adrenocortical carcinoma (ACC) is a rare and often fatal cancer of the peripheral domain of the gland, the adrenal cortex. Recent research in adrenal development, homeostasis, and disease have refined our understanding of the cellular and molecular programs controlling cortical growth and renewal, uncovering crucial clues into how physiologic programs are hijacked in early and late stages of malignant neoplasia. Alongside these studies, genome-wide approaches to examine adrenocortical tumors have transformed our understanding of ACC biology, and revealed that ACC is composed of distinct molecular subtypes associated with favorable, intermediate, and dismal clinical outcomes. The homogeneous transcriptional and epigenetic programs prevailing in each ACC subtype suggest likely susceptibility to any of a plethora of existing and novel targeted agents, with the caveat that therapeutic response may ultimately be limited by cancer cell plasticity. Despite enormous biomedical research advances in the last decade, the only potentially curative therapy for ACC to date is primary surgical resection, and up to 75% of patients will develop metastatic disease refractory to standard-of-care adjuvant mitotane and cytotoxic chemotherapy. A comprehensive, integrated, and current bench-to-bedside understanding of our field's investigations into adrenocortical physiology and neoplasia is crucial to developing novel clinical tools and approaches to equip the one-in-a-million patient fighting this devastating disease.

The role of molecular profiling in adrenocortical carcinoma

Adrenocortical carcinoma (ACC) is a rare, aggressive cancer with still partially unknown pathogenesis, heterogenous clinical behaviour and no effective treatment for advanced stages. Therefore, there is an urgent clinical unmet need for better prognostication strategies, innovative therapies and significant improvement of the management of the individual patients. In this review, we summarize available studies on molecular prognostic markers and markers predictive of response to standard therapies as well as newly proposed drug targets in sporadic ACC. We include in vitro studies and available clinical trials, focusing on alterations at the DNA, RNA and epigenetic levels. We also discuss the potential of biomarkers to be implemented in a clinical routine workflow for improved ACC patient care.

Was It an Adrenocortical Adenoma or an Adrenocortical Carcinoma? Limitation of the Weiss Scoring System in Determining the Malignant Potential of Adrenocortical Tumor: Report on Two Cases

Background

Adrenocortical carcinoma (ACC) is a rare endocrine malignancy. An accurate diagnosis of ACC is of paramount importance as it greatly impacts the management and prognosis of a patient. However, the differentiation between early stage, low-grade ACC and adrenocortical adenoma (ACA) may not always be straightforward. The recommended classification system, namely, the Weiss scoring system, is not without flaws. We herein report two cases of ACC which were initially diagnosed as ACA according to the Weiss scoring system but developed distant metastases in subsequent years. Case Presentation. Case 1: A 60-year-old Chinese woman presented with a recent onset of worsening of blood pressure control and clinical features of Cushing's syndrome. Investigations confirmed ACTH-independent endogenous hypercortisolism, and a CT abdomen showed a 6 cm right adrenal mass. Twenty-four-hour urine steroid profiling revealed co-secretion of adrenal androgens and atypical steroid metabolites. Laparoscopic right adrenalectomy was performed, and pathology of the tumor was classified as an ACA by the Weiss scoring system. Four years later, the patient presented with an abrupt onset of severe hypercortisolism and was found to have a metastatic recurrence in the liver and peritoneum. The patient received a combination of mitotane, systemic chemotherapy, and palliative debulking surgery and succumbed 8.5 years after the initial presentation due to respiratory failure with extensive pulmonary metastases. Case 2: A 68-year-old Chinese woman presented with acute bilateral pulmonary embolism and was found to have a 3 cm left adrenal mass. Hormonal workup confirmed ACTH-independent endogenous hypercortisolism, and laparoscopic left adrenalectomy revealed an ACA according to the Weiss scoring system. Five years later, she presented with recurrent hypercortisolism due to hepatic and peritoneal metastases. The patient had progressive disease despite mitotane therapy and succumbed 7 years after initial presentation.

Conclusions

Although the Weiss scoring system is recommended as the reference pathological classification system to diagnose adrenocortical carcinoma, there remain tumors of borderline malignant potential which may escape accurate classification. Various alternative classification systems and algorithms exist but none are proven to be perfect. Clinicians should recognize the potential limitation of these histological criteria and scoring systems and incorporate other clinical parameters, such as the pattern of hormonal secretion, urinary steroid profiling, and radiographic features, to improve the prognostication and surveillance strategy of these tumors.

Pediatric adrenocortical carcinoma

Adrenocortical carcinoma (ACC) is a rare endocrine malignancy of the adrenal gland with an unfavorable prognosis. It is rare in the pediatric population, with an incidence of 0.2-0.3 patients per million in patients under 20 years old. It is primarily associated with Li-Fraumeni and Beckwith-Wiedemann tumor predisposition syndromes in children. The incidence of pediatric ACC is 10-15fold higher in southern Brazil due to a higher prevalence of TP53 mutation associated with Li-Fraumeni syndrome in that population. Current treatment protocols are derived from adult ACC and consist of surgery and/or chemotherapy with etoposide, doxorubicin, and cisplatin (EDP) with mitotane. Limited research has been reported on other treatment modalities for pediatric ACC, including mitotane, pembrolizumab, cabozantinib, and chimeric antigen receptor autologous cell (CAR-T) therapy.

Molecular genotyping of adrenocortical carcinoma: a systematic analysis of published literature 2019-2021

PURPOSE OF REVIEW

comprehensive molecular characterization of adrenocortical carcinoma (ACC) through next-generation sequencing and bioinformatics analyses is expanding the number of targets with potential prognostic and therapeutic value. We performed a critical review of recent published literature on genotyping of ACC.

RECENT FINDINGS

423 studies were published between 2019 and 2021. After manual curation we summarized selected evidence in two thematic areas: germline deoxyribonucleic acid (DNA) variations, genomic alterations and prognosis.

SUMMARY

the evolving genomic landscape of ACC requires target validation in terms of prognostic and predictive value within scientific consortia. Although the existing multiple driver genes are difficult targets in the perspective of precision oncology, alterations in DNA damage repair genes or in promoter hypermethylation could open new venues for repurposing of existing drugs in ACC.

Adrenal Cortex Development and Maintenance: Knowledge Acquired From Mouse Models

The adrenal cortex is an endocrine organ organized into concentric zones that are specialized to produce specific steroid hormones essential for life. The development and maintenance of the adrenal cortex are complex, as a fetal adrenal is first formed from a common primordium with the gonads, followed by its separation in a distinct primordium, the invasion of the adrenal primordium by neural crest-derived cells to form the medulla, and finally its encapsulation. The fetal cortex is then replaced by a definitive cortex, which will establish zonation and be maintained throughout life by regeneration relying on the proliferation, centripetal migration, and differentiation of several stem/progenitor cell populations whose activities are sex-specific. Here, we highlight the advances made, using transgenic mouse models, to delineate the molecular mechanisms regulating these processes.

Steroid Sulfation in Adrenal Tumors

CONTEXT

The adrenal cortex produces specific steroid hormones including steroid sulfates such as dehydroepiandrosterone sulfate (DHEAS), the most abundant steroid hormone in the human circulation. Steroid sulfation involves a multistep enzyme machinery that may be impaired by inborn errors of steroid metabolism. Emerging data suggest a role of steroid sulfates in the pathophysiology of adrenal tumors and as potential biomarkers.

EVIDENCE ACQUISITION

Selective literature search using "steroid," "sulfat*," "adrenal," "transport," "mass spectrometry" and related terms in different combinations.

EVIDENCE SYNTHESIS

A recent study highlighted the tissue abundance of estrogen sulfates to be of prognostic impact in adrenocortical carcinoma tissue samples using matrix-assisted laser desorption ionization mass spectrometry imaging. General mechanisms of sulfate uptake, activation, and transfer to substrate steroids are reasonably well understood. Key aspects of this pathway, however, have not been investigated in detail in the adrenal; these include the regulation of substrate specificity and the secretion of sulfated steroids. Both for the adrenal and targeted peripheral tissues, steroid sulfates may have relevant biological actions beyond their cognate nuclear receptors after desulfation. Impaired steroid sulfation such as low DHEAS in Cushing adenomas is of diagnostic utility, but more comprehensive studies are lacking. In bioanalytics, the requirement of deconjugation for gas-chromatography/mass-spectrometry has precluded the study of steroid sulfates for a long time. This limitation may be overcome by liquid chromatography/tandem mass spectrometry.

CONCLUSIONS

A role of steroid sulfation in the pathophysiology of adrenal tumors has been suggested and a diagnostic utility of steroid sulfates as biomarkers is likely. Recent analytical developments may target sulfated steroids specifically.

Identification of novel lipid metabolic biomarkers associated with poor adrenocortical carcinoma prognosis using integrated bioinformatics

BACKGROUND

Adrenocortical carcinoma while rare, often presents with advanced metastatic disease carrying a 5-year survival of <15%. Despite adrenocortical carcinoma tumors having high avidity for cholesterol, the role of lipids in adrenocortical carcinoma has not been well described. Therefore, we performed an integrated bioinformatic analysis to identify novel lipid biomarkers correlating with poor survival that may help identify adrenocortical carcinoma tumor progression or therapy resistance.

METHODS

A meta-analysis of collated adrenocortical carcinoma studies from the correlation engine identified lipid metabolism genes differentially expressed between adrenocortical carcinoma and the normal adrenal, which were then selected for enrichment analysis by the Database for Annotation, Visualization and Integrated Discovery database. A protein-protein interaction network of genes was constructed using Search Tool for the Retrieval of Interacting Genes/Proteins and Cytoscape. Top hub genes identified were validated using the Xena database. Survival analysis of hub genes was performed in the R2 genomic analysis platform using The Cancer Genome Atlas program data set.

RESULTS

Examination of pathways by correlation engine identified a unique subset of lipid metabolism-related genes that are differentially regulated in adrenocortical carcinoma tumors versus normal tissues (P < .01). Enrichment pathway analysis in Database for Annotation, Visualization and Integrated Discovery indicated that genes involved in sphingolipid, steroid, and peroxisome proliferator-activated receptor-α metabolism is upregulated in adrenocortical carcinoma, whereas glycerol phospholipid, fatty acid, and phosphatidylinositol metabolism are downregulated. Survival analysis of differentially regulated genes indicated that upregulation of SGPL1, FDFT1, SQLE and downregulation of PIK3C2B, PIK3CD, SYNJ2, DGAT1, PLA2G16, PLD1, GPD1 are all significantly associated with poor overall survival (P < .05) in adrenocortical carcinoma patients.

CONCLUSION

Upregulation of sphingolipid and steroid synthesis genes and downregulation of phosphatidylinositol and glycerol phospholipid metabolism are associated with worse survival in patients with adrenocortical carcinoma.

The Challenging Pharmacokinetics of Mitotane: An Old Drug in Need of New Packaging

Adrenocortical carcinoma (ACC) is a malignant tumor originating from the adrenal gland cortex with a heterogeneous but overall dismal prognosis in advanced stages. For more than 50 years, mitotane has remained a cornerstone for the treatment of ACC as adjuvant and palliative therapy. It has a very poor aqueous solubility of 0.1 mg/l and high partition coefficient in octanol/water (log P) value of 6. The commercially available dosage form is 500 mg tablets (Lysodren^®). Even at doses up to 6 g/day (12 tablets in divided doses) for several months, > 50% patients do not achieve therapeutic plasma concentration > 14 mg/l due to poor water solubility, large volume of distribution and inter/intra-individual variability in bioavailability. This article aims to give a concise update of the clinical challenges associated with the administration of high-dose mitotane oral therapy which encompass the issues of poor bioavailability, difficult-to-predict pharmacokinetics and associated adverse events. Moreover, we present recent efforts to improve mitotane formulations. Their success has been limited, and we therefore propose an injectable mitotane formulation instead of oral administration, which could bypass many of the main issues associated with high-dose oral mitotane therapy. A parenteral administration of mitotane could not only help to alleviate the adverse effects but also circumvent the variable oral absorption, give better control over therapeutic plasma mitotane concentration and potentially shorten the time to achieve therapeutic drug plasma concentrations considerably.

Mitotane as tablet form is currently the standard treatment for adrenocortical carcinoma. It has been used for 5 decades but suffers from highly variable responses in patients, subsequent adverse effects and overall lower response rate. This can be fundamentally linked to the exceedingly poor water solubility of mitotane itself. In terms of enhancing water solubility, a few research groups have attempted to develop better formulations of mitotane to overcome the issues associated with tablet dosage form. However, the success rate was limited, and these formulations did not make it into the clinics. In this article, we have comprehensively reviewed the properties of these formulations and discuss the reasons for their limited utility. Furthermore, we discuss a recently developed mitotane nanoformulation that led us to propose a novel approach to mitotane therapy, where intravenous delivery supplements the standard oral administration. With this article, we combine the current state of knowledge as a single piece of information about the various problems associated with the use of mitotane tablets, and herein we postulate the development of a new injectable mitotane formulation, which can potentially circumvent the major problems associated to mitotane's poor water solubility.

Histological scores and tumor size on stage II in adrenocortical carcinomas

Adrenocortical carcinomas (ACC) are aggressive tumors with a poor prognosis. Histological scores are advised for the diagnosis, however, there are borderline cases that may be misjudged as adrenocortical adenomas (ACA). The three main scores used are: Weiss Modified System (WMS), Reticulin Algorithm (RA), and Helsinki Score (HS). We intend to compare the accuracy of the three scores in ACC diagnosis and to identify predictive factors of overall survival (OS). Retrospective study (2004–2016) at Centro Hospitalar e Universitário de Coimbra of the adrenal tumors, classified as ACC or ACA, with a history of posterior tumor relapse/metastases, without lesions in the contralateral adrenal gland: 13F and 6M, with a median age of 51 ± 12.41 years. Nodules’ median size was 9.20 ± 6.2 cm. Patients had a median OS of 52 ± 18.6 months, with 57.9% and 46.3%, at 3 and 5 years. Seven patients had local recurrence and nine had metastases. Thirteen cases were in stage II. The WMS and the HS allowed a diagnosis of ACC in 15 cases and the RA defined ACC in 17 cases. All cases had, at least, focal disruption of the reticulin framework. More than 5 mitosis/50 HPF was associated with worse OS: 49.67 ± 21.43 versus 108.86 ± 14.02 months (p = 0.026). In patients with stage II, tumor size ⩾10 cm was associated with worse OS: 19.25 ± 7.15 versus 96.11 ± 16.7 months (p = 0.007), confirmed by multivariate analysis (p = 0.031). The correct diagnosis of ACC is a pathologist responsibility. The RA seems the most accurate. Any loss of the reticulin framework should raise awareness for malignancy. In patients on stage II, a size ⩾10 cm is a predictor of worse prognosis.

Inhibition of Aurora kinase A activity enhances the antitumor response of beta-catenin blockade in human adrenocortical cancer cells

Adrenocortical cancer (ACC) is a rare and aggressive type of endocrine tumor with high risk of recurrence and metastasis. The overall survival of patients diagnosed with ACC is low and treatment for metastatic stages remain limited to mitotane, which has low efficiency in advanced stages of the disease and is associated with high toxicity. Therefore, identification of new biological targets to improve ACC treatment is crucial. Blockade of the Wnt/beta-catenin pathway decreased adrenal steroidogenesis and increased apoptosis of NCI-H295 human ACC cells, in vitro and in a xenograft mouse model. Aurora kinases play important roles in cell division during the G1-M phase and their aberrant expression is correlated with a poor prognosis in different types of tumors. Hence, we hypothesized that inhibition of aurora kinases activity combined with the beta-catenin pathway blockade would improve the impairment of ACC cell growth in vitro. We studied the combinatorial effects of AMG 900, an aurora kinase inhibitor and PNU-74654, a beta-catenin pathway blocker, on proliferation, survival and tumor progression in multiple ACC cell lines: NCI-H295, CU-ACC1 and CU-ACC2. Exposure of ACC cells to the combination of AMG 900 with PNU-74654 decreased cell proliferation and viability compared to either treatment alone. In addition, AMG 900 inhibited cell invasion and clonogenesis compared to PNU-74654, and the combination showed no greater effects. In contrast, PNU-74654 was more effective in decreasing cortisol secretion. These data suggest that inhibition of aurora kinases activity combined with blockade of the beta-catenin pathway may provide a combinatorial approach for targeting ACC tumors.

Tumor Microenvironment in Adrenocortical Carcinoma: Barrier to Immunotherapy Success?

Adrenocortical carcinoma is a rare malignancy with aggressive behavior, with up to 40% of patients presenting with metastases at the time of diagnosis. Both conventional chemotherapeutic regimens and novel immunotherapeutic agents, many of which are currently being tested in ongoing clinical trials, have yielded modest results so far, bringing the need for a deeper understanding of adrenal cancer behavior to the forefront. In the recent years, the tumor microenvironment has emerged as a major determinant of cancer response to immunotherapy and an increasing number of studies on other solid tumors have focused on manipulating the microenvironment in the favor of the host and discovering new potential target molecules. In the present review we aim to explore the characteristics of adrenocortical cancer's microenvironment, highlighting the mechanisms of immune evasion responsible for the modest immunotherapeutic results, and identify novel potential strategies.

Epithelial and Mesenchymal Markers in Adrenocortical Tissues: How Mesenchymal Are Adrenocortical Tissues?

A clinically relevant proportion of adrenocortical carcinoma (ACC) cases shows a tendency to metastatic spread. The objective was to determine whether the epithelial to mesenchymal transition (EMT), a mechanism associated with metastasizing in several epithelial cancers, might play a crucial role in ACC. 138 ACC, 29 adrenocortical adenomas (ACA), three normal adrenal glands (NAG), and control tissue samples were assessed for the expression of epithelial (E-cadherin and EpCAM) and mesenchymal (N-cadherin, SLUG and SNAIL) markers by immunohistochemistry. Using real-time RT-PCR we quantified the alternative isoform splicing of FGFR 2 and 3, another known indicator of EMT. We also assessed the impact of these markers on clinical outcome. Results show that both normal and neoplastic adrenocortical tissues lacked expression of epithelial markers but strongly expressed mesenchymal markers N-cadherin and SLUG. FGFR isoform splicing confirmed higher similarity of adrenocortical tissues to mesenchymal compared to epithelial tissues. In ACC, higher SLUG expression was associated with clinical markers indicating aggressiveness, while N-cadherin expression inversely associated with these markers. In conclusion, we could not find any indication of EMT as all adrenocortical tissues lacked expression of epithelial markers and exhibited closer similarity to mesenchymal tissues. However, while N-cadherin might play a positive role in tissue structure upkeep, SLUG seems to be associated with a more aggressive phenotype.

Construction of a risk signature for adrenocortical carcinoma using immune-related genes

Background

Adrenocortical carcinoma (ACC) is considered a rare tumor with a dismal prognosis. Expression of immune-related genes (IRGs) in ACC and correlations between IRGs and ACC prognosis were assessed using The Cancer Genome Atlas (TCGA) and Genotype-Tissue Expression (GTEx) databases.

Methods

To preliminarily predict immune cell infiltration, an immune score was calculated using ESTIMATE. Differentially expressed IRGs were screened, and potential biological functions were investigated. We then performed univariate Cox regression to identify IRGs associated with survival, and the regulatory mechanisms of IRGs associated with survival were predicted. We built a risk signature through multivariate Cox regression to evaluate patient overall survival (OS).

Results

A high immune score predicted a good prognosis and an early clinical stage in ACC. We identified 30 IRGs associated with survival and then predicted associated regulatory mechanisms via protein-protein interaction (PPI) and transcription factor (TF) regulatory networks. The risk signature established by multivariate Cox regression correlated significantly with prognosis in ACC.

Conclusions

The vital roles of IRGs in ACC were assessed, and the risk signature obtained based on IRGs associated with survival independently predicted ACC prognosis.

Wnt/β-catenin activation cooperates with loss of p53 to cause adrenocortical carcinoma in mice

Adrenocortical carcinoma (ACC) is a rare and aggressive malignancy with limited therapeutic options. The lack of mouse models that recapitulate the genetics of ACC has hampered progress in the field. We analyzed The Cancer Genome Atlas (TCGA) dataset for ACC and found that patients harboring alterations in both p53/Rb and Wnt/β-catenin signaling pathways show a worse prognosis compared with patients that harbored alterations in only one. To model this, we utilized the Cyp11b2(AS)^Cre mouse line to generate mice with adrenocortical-specific Wnt/β-catenin activation, Trp53 deletion, or the combination of both. Mice with targeted Wnt/β-catenin activation or Trp53 deletion showed no changes associated with tumor formation. In contrast, alterations in both pathways led to ACC with pulmonary metastases. Similar to ACCs in humans, these tumors produced increased levels of corticosterone and aldosterone and showed a high proliferation index. Gene expression analysis revealed that mouse tumors exhibited downregulation of Star and Cyp11b1 and upregulation of Ezh2, similar to ACC patients with a poor prognosis. Altogether, these data show that altering both Wnt/β-catenin and p53/Rb signaling is sufficient to drive ACC in mouse. This autochthonous model of ACC represents a new tool to investigate the biology of ACC and to identify new treatment strategies.

Update on in-vivo preclinical research models in adrenocortical carcinoma

PURPOSE OF REVIEW

The aim of this review is to summarize recent advances on development of in vivo preclinical models of adrenocortical carcinoma (ACC).

RECENT FINDINGS

Significant progress has been achieved in the underlying molecular mechanisms of adrenocortical tumorigenesis over the last decade, and recent comprehensive profiling analysis of ACC tumors identified several genetic and molecular drivers of this disease. Therapeutic breakthroughs, however, have been limited because of the lack of preclinical models recapitulating the molecular features and heterogeneity of the tumors. Recent publications on genetically engineered mouse models and development of patient-derived ACC xenografts in both nude mice and humanized mice now provide researchers with novel tools to explore therapeutic targets in the context of heterogeneity and tumor microenvironment in human ACC.

SUMMARY

We review current in-vivo models of ACC and discuss potential therapeutic opportunities that have emerged from these studies.

Past, Present and Future of Epigenetics in Adrenocortical Carcinoma

DNA methylation profiling has been suggested a reliable technique to distinguish between benign and malignant adrenocortical tumors, a process which with current diagnostic methods remains challenging and lacks diagnostic accuracy of borderline tumors. Accurate distinction between benign and malignant adrenal tumors is of the essence, since ACC is a rare but aggressive endocrine disease with an annual incidence of about 2.0 cases per million people per year. The estimated five-year overall survival rate for ACC patients is <50%. However, available treatment regimens are limited, in which a radical surgical resection is the only curable option. Nevertheless, up to 85% of patients with radical resection show recurrence of the local disease often with concurrent metastases. Adrenolytic therapy with mitotane, administered alone or in combination with cytotoxic agents, is currently the primary (palliative) treatment for patients with advanced ACC and is increasingly used in adjuvant setting to prevent recurrence. Prognostic stratification is important in order to individualize adjuvant therapies. On April 1, 2020, there were 7404 publications on adrenocortical carcinoma (adrenocortical carcinoma) OR adrenocortical carcinoma [MeSH Terms]) OR adrenal cortex cancer[MeSH Terms]) OR adrenal cortical carcinoma [MeSH Terms]) OR adrenal cortex neoplasm [MeSH Terms]) OR adrenocortical cancer [MeSH Terms]), yet the underlying pathophysiology and characteristics of ACC is not fully understood. Knowledge on epigenetic alterations in the process of adrenal tumorigenesis is rapidly increasing and will add to a better understanding of the pathogenesis of ACC. DNA methylation profiling has been heralded as a promising method in the prognostication of ACC. This review summarizes recent findings on epigenetics of ACC and its role in diagnosis, prognosis and therapeutic strategies.

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.

Leptomeningeal Metastasis from Adrenocortical Carcinoma: A Case Report

Adrenocortical carcinoma (ACC) is an uncommon endocrine malignancy with limited treatment options. While the overall 5-year survival rate in patients with ACC is 35%, the disease is often rapidly progressive with long-term survival in only 5% of patients. Although tumor stage, grade, and excess hormonal activity predict unfavorable prognosis, additional biomarkers are needed to identify patients with aggressive disease. A 23-year-old woman presented with rapidly progressing signs and symptoms of Cushing's syndrome, with associated abdominal pain and fullness. Evaluation revealed a large left adrenal mass which had developed over 8 months. En bloc surgical resection was performed by an endocrine surgeon, and pathology revealed adrenocortical carcinoma with Ki67 of 60%. Despite adjuvant treatment with mitotane and etoposide-doxorubicin-carboplatin chemotherapy, the patient had rapid disease progression with metastatic spread to liver, lung, bone, brain, and leptomeningies, and she died 11 months after the initial diagnosis. Subsequent analysis of the patient's tumor revealed mutations in TP53 and MEN1. RNA sequencing was compared against the the Cancer Genome Atlas data set and clustered with the high steroid, proliferative subtype, associated with the worst prognosis. The tumor also demonstrated a low BUB1B/PINK1 ratio and G0S2 hypermethylation, both predictive of very aggressive ACC. This case represents a subset of ACC characterized by rapid and fatal progression. Clinically available predictors as well as recently reported molecular signatures and biomarkers correlated with this tumor's aggressiveness, suggesting that development and validation of combinations of biomarkers may be useful in guiding personalized approaches to patients with ACC.

Tauroursodeoxycholic acid mediates endoplasmic reticulum stress and autophagy in adrenocortical carcinoma cells

Adrenocortical carcinoma (ACC) is an invasive tumor that occurs in the endocrine system. Increasing evidence has shown that endoplasmic reticulum (ER) stress and autophagy play an important role in tumor formation. Tauroursodeoxycholic acid (TUDCA) is an ER chemical chaperone that can alleviate ER stress. In the present study, TUDCA promoted the proliferation, migration and invasion of ACC SW-13 and NCI-H295R cells. Reverse transcription-quantitative PCR and western blot analysis showed that the expression of glucose-regulated protein 78, a promoter of ER stress, was decreased. The expression levels of protein kinase R (PKR)-like ER kinase and activating transcription factor 6 were correspondingly decreased, and the downstream proteins, C/EBP homologous protein and JNK, were also decreased. The expression levels of the autophagy factor microtubule-associated protein light chain 3-II/I and the anti-apoptotic factor Bcl-2 increased following TUDCA treatment, while the expression of the pro-apoptotic factor Bax decreased. TUDCA alleviated ER stress in ACC SW-13 and NCI-H295R cells and induced autophagy, thereby inhibiting ACC cell apoptosis. ER stress- and autophagy-related signaling pathways are involved in the occurrence of ACC, which may provide potential therapeutic targets for ACC treatment.

The Adipose Stem Cell as a Novel Metabolic Actor in Adrenocortical Carcinoma Progression: Evidence from an In Vitro Tumor Microenvironment Crosstalk Model

Metabolic interplay between the tumor microenvironment and cancer cells is a potential target for novel anti-cancer approaches. Among stromal components, adipocytes and adipose precursors have been shown to actively participate in tumor progression in several solid malignancies. In adrenocortical carcinoma (ACC), a rare endocrine neoplasia with a poor prognosis, cancer cells often infiltrate the fat mass surrounding the adrenal organ, enabling possible crosstalk with the adipose cells. Here, by using an in vitro co-culture system, we show that the interaction between adipose-derived stem cells (ASCs) and the adrenocortical cancer cell line H295R leads to metabolic and functional reprogramming of both cell types: cancer cells limit differentiation and increase proliferation of ASCs, which in turn support tumor growth and invasion. This effect associates with a shift from the paracrine cancer-promoting IGF2 axis towards an ASC-associated leptin axis, along with a shift in the SDF-1 axis towards CXCR7 expression in H295R cells. In conclusion, our findings suggest that adipose precursors, as pivotal components of the ACC microenvironment, promote cancer cell reprogramming and invasion, opening new perspectives for the development of more effective therapeutic approaches.

Nivolumab in Metastatic Adrenocortical Carcinoma: Results of a Phase 2 Trial

CONTEXT

Systemic treatment of metastatic adrenocortical carcinoma (ACC) remains limited to chemotherapy and mitotane. Preliminary evidence suggesting that antitumor immune responses can be elicited in ACC has fostered interest in checkpoint inhibitors such as anti-PD-1 nivolumab.

OBJECTIVE

The primary endpoint was objective response rate according to the response evaluation criteria in solid tumors. Secondary endpoints were progression-free survival (PFS), overall survival, and safety.

DESIGN

Single-arm, multicenter, phase 2 clinical trial with two-stage design.

SETTING

Comprehensive cancer center.

PATIENTS

Ten adult patients with metastatic ACC previously treated with platinum-based chemotherapy and/or mitotane as well as patients who declined front-line chemotherapy.

INTERVENTION

Nivolumab (240 mg) IV every 2 weeks.

RESULTS

Ten patients with metastatic ACC were enrolled between March and December 2016. The median number of doses of nivolumab administered was two. Three patients only received one treatment [one died of disease progression, one discontinued due to adverse events (AEs), one withdrew after beginning treatment]. The median PFS was 1.8 months. The median follow-up was 4.5 months (range, 0.1 to 25.6 months). Two patients had stable disease for a duration of 48 and 11 weeks, respectively. One patient had an unconfirmed partial response but discontinued the study due to an AE. Most AEs were grade 1/2. The most common grade 3/4 treatment-related AEs were aspartate aminotransferase and alanine aminotransferase elevations, mucositis, and odynophagia.

CONCLUSION

Nivolumab demonstrated modest antitumor activity in patients with advanced ACC. The nivolumab safety profile was consistent with previous clinical experience without any unexpected AEs in this population.

Targeting PDZ-binding kinase is anti-tumorigenic in novel preclinical models of ACC

Adrenocortical carcinoma (ACC) is an aggressive orphan malignancy with less than 35% 5-year survival and 75% recurrence. Surgery remains the primary therapy and mitotane, an adrenolytic, is the only FDA-approved drug with wide-range toxicities and poor tolerability. There are no targeted agents available to date. For the last three decades, H295R cell line and its xenograft were the only available preclinical models. We recently developed two new ACC patient-derived xenograft mouse models and corresponding cell lines (CU-ACC1 and CU-ACC2) to advance research in the field. Here, we have utilized these novel models along with H295R cells to establish the mitotic PDZ-binding kinase (PBK) as a promising therapeutic target. PBK is overexpressed in ACC samples and correlates with poor survival. We show that PBK is regulated by FOXM1 and targeting PBK via shRNA decreased cell proliferation, clonogenicity and anchorage-independent growth in ACC cell lines. PBK silencing inhibited pAkt, pp38MAPK and pHistone H3 altering the cell cycle. Therapeutically, targeting PBK with the small-molecule inhibitor HITOPK032 phenocopied PBK-specific modulation of pAkt and pHistone H3, but also induced apoptosis via activation of JNK. Consistent with in vitro findings, treatment of CU-ACC1 PDXs with HITOPK032 significantly reduced tumor growth by 5-fold (P < 0.01). Treated tumor tissues demonstrated increased rates of apoptosis and JNK activation, with decreased pAkt and Histone H3 phosphorylation, consistent with effects observed in ACC cell lines. Together these studies elucidate the mechanism of PBK in ACC tumorigenesis and establish the potential therapeutic potential of HITOPK032 in ACC patients.

Screening and Identification of Potential Prognostic Biomarkers in Adrenocortical Carcinoma

Objective: Adrenocortical carcinoma (ACC) is a rare but aggressive malignant cancer that has been attracting growing attention over recent decades. This study aims to integrate protein interaction networks with gene expression profiles to identify potential biomarkers with prognostic value in silico. Methods: Three microarray data sets were downloaded from the Gene Expression Omnibus (GEO) database to identify differentially expressed genes (DEGs) according to the normalization annotation information. Enrichment analyses were utilized to describe biological functions. A protein-protein interaction network (PPI) of the DEGs was developed, and the modules were analyzed using STRING and Cytoscape. LASSO Cox regression was used to identify independent prognostic factors. The Kaplan-Meier method for the integrated expression score was applied to analyze survival outcomes. A receiver operating characteristic (ROC) curve was constructed with area under curve (AUC) analysis to determine the diagnostic ability of the candidate biomarkers. Results: A total of 150 DEGs and 24 significant hub genes with functional enrichment were identified as candidate prognostic biomarkers. LASSO Cox regression suggested that ZWINT, PRC1, CDKN3, CDK1 and CCNA2 were independent prognostic factors in ACC. In multivariate Cox analysis, the integrated expression scores of the modules showed statistical significance in predicting disease-free survival (DFS, P = 0.019) and overall survival (OS, P < 0.001). Meanwhile, ROC curves were generated to validate the ability of the Cox model to predict prognosis. The AUC index for the integrated genes scores was 0.861 (P < 0.0001). Conclusion: In conclusion, the present study identifies DEGs and hub genes that may be involved in poor prognosis and early recurrence of ACC. The expression levels of ZWINT, PRC1, CDKN3, CDK1 and CCNA2 are of high prognostic value, and may help us understand better the underlying carcinogenesis or progression of ACC. Further studies are required to elucidate molecular pathogenesis and alteration in signaling pathways for these genes in ACC.

Identification of key modules and prognostic markers in adrenocortical carcinoma by weighted gene co-expression network analysis

Adrenocortical carcinoma (ACC) is a rare and aggressive cancer with a high relapse rate and limited treatment options. Therefore, the identification of potential prognostic markers in patients with ACC may improve early detection, survival rates and may additionally provide novel insights into the early detection of recurrence. In the present study, clinical traits and RNA-seq data of 79 patients with ACC were obtained from The Cancer Genome Atlas (TCGA). Weighted gene co-expression network analysis was carried out and 17 distinct co-expression modules were built to examine the association between the modules and the clinical traits. Of the 17 modules, two co-expression modules, which contained 214 and 168 genes, were significantly correlated with two clinical traits, tumor stage and vital status. Functional enrichment analysis was performed on the selected modules. The results showed that one of the modules was primarily enriched in cell division and the other module was enriched in metabolic pathways, suggesting their involvement in tumor progression. Furthermore, cyclin dependent kinase 1 (CDK1) and ubiquitin C (UBC) were identified as hub genes in both modules. Survival analysis revealed that the high expression of the hub genes significantly correlated with the poor survival rate of patients, suggesting that CDK1 and UBC have vital roles in the progression of ACC. In the present study, a co-expression gene module of ACC was provided and the prognostic genes that may serve as new diagnostic markers in the future were defined.

Molecular Drivers of Potential Immunotherapy Failure in Adrenocortical Carcinoma

Adrenocortical carcinoma (ACC) is a rare, highly aggressive cancer, often insensitive to conventional chemotherapeutics agents. Early diagnosis, followed by radical surgical resection plus/minus adjuvant mitotane therapy, is nowadays the only valuable option. Unfortunately, one out of four patients has metastatic disease at diagnosis and most of radically resected ACC patients are destined to recur with local or metastatic disease. Numerous efforts aimed at identifying molecular alterations crucial for ACC pathogenesis have been extensively conducted, with the hope to develop new treatments. Indeed, multiple genes and pathways have been identified as potentially targetable in ACC patients; however, despite the strong preclinical rationale, translational findings to clinical trials led to date to disappointing results. The immunotherapeutic intervention targeting T-cell checkpoint molecules has been proposed as well, but results obtained in early studies indicate that ACC patients would be unlikely to benefit from immunotherapy. Genetic alterations of different pathways involved in ACC carcinogenesis are also known substrates of resistance to immunotherapy. Among them, β-catenin gene CTNNB1 and TP53 gene are frequently mutated in ACC samples. Overactivation of the β-catenin pathway and loss of p53 protein function are potential tumor-intrinsic factors that, impacting on the ability of ACC cells to recruit dendritic cells, leading to T-cell exclusion, put this tumor among those that are potentially resistant to immunotherapy. Moreover, the steroid phenotype, which implies glucocorticoids hypersecretion in a subset of ACC, contributes to generating an immunosuppressive microenvironment. Here, we review clinical results of immunotherapy in ACC and we highlight molecular mechanisms driving immunotherapy failure in ACC, suggesting possible approaches to overcome resistance.