Mitotane exhibits dual effects on steroidogenic enzymes gene transcription under basal and cAMP-stimulating microenvironments in NCI-H295 cells

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.

Adjuvant therapy in adrenocortical carcinoma: prognostic factors and treatment options

Adrenocortical carcinoma (ACC) is a rare cancer with high recurrence rates and heterogeneous clinical behavior. The role of adjuvant therapy remains unclear because of the challenges in collecting high-quality data for a rare cancer. The current treatment recommendations and guidelines for adjuvant therapy are mostly derived retrospectively from national databases and the treatment outcomes of patients seen in referral centers. To better select patients for adjuvant therapy, multiple factors need to be considered including staging, markers of cellular proliferation (such as Ki67%), resection margins, hormonal function, and possibly genetic alterations of the tumor as well as patient-related factors such as age and performance status. Adjuvant mitotane remains the most commonly used adjuvant therapy in ACC based on clinical practice guidelines, though emerging data from ADIUVO trial (mitotane vs observation in low-risk ACC) suggest that mitotane use in low-risk patients may not be needed. An ongoing clinical trial (ADIUVO-2) is evaluating the role of mitotane vs mitotane combined with chemotherapy in high-risk ACC. The use of adjuvant therapy has been controversial but can be justified in select patients with positive resection margins or after the resection of localized recurrence. A prospective study is needed to study the role of adjuvant radiation in ACC as radiation is expected to help only with local control without impact on distant microscopic metastases. There are no recommendations or published data about using adjuvant immunotherapy in ACC, but this may be a future study after establishing the efficacy and safety profile of immunotherapy in metastatic ACC.

Mitotane treatment in adrenocortical carcinoma: mechanisms of action and predictive markers of response to therapy

INTRODUCTION

Adrenocortical carcinoma (ACC) is a rare malignancy with a high risk of recurrence even in cases with complete surgical tumor resection. Mitotane represents the cornerstone of the adjuvant therapy as well as the first line of medical treatment in advanced cases. However, evidence on mitotane efficacy is mostly based on retrospective studies and the use of mitotane continues to represent a clinical challenge.

EVIDENCE ACQUISITION

Mitotane causes selective damage to adrenocortical cells, causing an increase of cell apoptosis through a disruption of mitochondria and the induction of the endoplasmic reticulum stress. Different clinical and molecular markers predicting response to mitotane have been proposed with uncertain results. Attainment of mitotane plasma levels within the target range of 14 to 20 mg/L represent the strongest predictor of mitotane effectiveness both in adjuvant and advanced tumor setting. The occurrence of late recurrence after primary ACC diagnosis and changes in metabolic activity on FDG-PET are only weakly associated with mitotane response. Among the proposed molecular markers associated with mitotane efficacy, the investigation of the CYP2W1*6 and CYP2B6*6 single nucleotide polymorphisms appears to be currently the most promising predictive molecular markers of mitotane therapy. However, none of the evaluated markers has been validated for clinical use.

CONCLUSIONS

In the era of precision medicine, a better insight into mitotane molecular mechanisms as well as the potential use in the daily clinical practice of clinical parameters and molecular markers predicting the individual response to mitotane are urgently needed.

Molecular Mechanisms of Mitotane Action in Adrenocortical Cancer Based on In Vitro Studies

Simple Summary

Mitotane is the only approved drug for the treatment of advanced adrenocortical carcinoma and for postoperative adjuvant therapy. It is known that mitotane destroys the adrenal cortex impairing steroidogenesis, although its exact molecular mechanism is still unclear. However, confounding factors affecting in vitro experiments could reduce the relevance of the studies. In this review, we explore in vitro studies on mitotane effects, highlighting how different experimental conditions might contribute to the controversial findings. On this basis, it may be necessary to re-evaluate the experiments taking into account their potential confounding factors such as cell strains, culture serum, lipoprotein concentration, and culture passages, which could hide important molecular results. As a consequence, the identification of novel pharmacological molecular pathways might be used in the future to implement personalized therapy, maximizing the benefit of mitotane treatment while minimizing its toxicity.

Abstract

Mitotane is the only approved drug for the treatment of advanced adrenocortical carcinoma and is increasingly used for postoperative adjuvant therapy. Mitotane action involves the deregulation of cytochromes P450 enzymes, depolarization of mitochondrial membranes, and accumulation of free cholesterol, leading to cell death. Although it is known that mitotane destroys the adrenal cortex and impairs steroidogenesis, its exact mechanism of action is still unclear. The most used cell models are H295-derived cell strains and SW13 cell lines. The diverging results obtained in presumably identical cell lines highlight the need for a stable in vitro model and/or a standard methodology to perform experiments on H295 strains. The presence of several enzymatic targets responsive to mitotane in mitochondria and mitochondria-associated membranes causes progressive alteration in mitochondrial structure when cells were exposed to mitotane. Confounding factors of culture affecting in vitro experiments could reduce the significance of any molecular mechanism identified in vitro. To ensure experimental reproducibility, particular care should be taken in the choice of culture conditions: aspects such as cell strains, culture serum, lipoproteins concentration, and culture passages should be carefully considered and explicated in the presentation of results. We aimed to review in vitro studies on mitotane effects, highlighting how different experimental conditions might contribute to the controversial findings. If the concerns pointed out in this review will be overcome, the new insights into mitotane mechanism of action observed in-vitro could allow the identification of novel pharmacological molecular pathways to be used to implement personalized therapy.

Pharmacological profile and effects of mitotane in adrenocortical carcinoma

Mitotane is the only adrenolytic drug approved by the Food and Drug Administration for treating adrenocortical carcinoma (ACC). This drug has cytotoxic effects on tumour tissues; it induces cell death and antisecretory effects on adrenal cells by inhibiting the synthesis of adrenocortical steroids, which are involved in the pathogenesis of ACC. However, high doses of mitotane are usually necessary to reach the therapeutic plasma concentration, which may result in several adverse effects. This suggests that important pharmacological processes, such as first pass metabolism, tissue accumulation and extensive time for drug elimination, are associated with mitotane administration. Few studies have reported the pharmacological aspects and therapeutic effects of mitotane. Therefore, the aim of this review was to summarize the chemistry, pharmacokinetics and pharmacodynamics, and therapeutic and toxic effects of mitotane. This review also discusses new perspectives of mitotane formulation that are currently under investigation. Understanding the pharmacological profile of mitotane can improve the monitoring and efficacy of this drug in ACC treatment and can provide useful information for the development of new drugs with specific action against ACC with fewer adverse effects.

Determination of the roles of GREM1 gene in granulosa cell proliferation and steroidogenesis of hen ovarian prehierarchical follicles

Gremlin genes are known members of the DAN family of bone morphogenetic protein (BMP) antagonists, but their functions and regulatory mechanisms in ovarian follicular development of chicken remain unknown. The current study was designed to investigate the mRNA expression patterns of gremlin1 gene (GREM1) and its protein location in the follicles sampled, and to explore the biological effect of GREM1 on the prehierarchical follicular development. This work revealed that chicken GREM1 mRNA exhibits a constant expression level across all the prehierarchical follicles (PFs) from 1-4 mm to 7-8 mm in diameter, and the preovulatory follicles (from F6 to F1) by using RT-qPCR (P > 0.05). The GREM1 protein is predominantly expressed in the oocytes and granulosa cells (GCs) of the PFs by immunohistochemistry. Furthermore, our data demonstrated that siRNA-mediated knockdown of GREM1 in the GCs resulted in a significant reduction in cell proliferation (P < 0.001); conversely, overexpression of GREM1 in the GCs led to a remarkable increase in cell proliferation (P < 0.001). Interestingly, the expression levels of proliferating cell nuclear antigen (PCNA) and cyclin D2 (CCND2) mRNA and proteins were notably increased when GREM1 expression was upregulated in the GCs (P < 0.01), however, the expression levels of CYP11A1 and StAR were markedly downregulated (P < 0.01). The current results showed that GREM1 gene plays a stimulatory role in GC proliferation during growth and development of the prehierarchical follicles in vitro but an inhibitory role in GC differentiation and steroidogenesis of the hen ovary follicles.

New perspectives for mitotane treatment of adrenocortical carcinoma

Adrenocortical carcinoma (ACC) is an aggressive cancer characterized by poor survival. Apart from radical surgery, there is a limited range of therapeutic options and mitotane remains the cornerstone of medical treatment of ACC in either adjuvant or palliative settings. The aim of adjuvant mitotane therapy is to reduce the risk of ACC recurrence following surgical removal of the tumor. Use of mitotane in an adjuvant setting is off-label, but the recent guidelines endorsed by the European Society of Endocrinology (ESE) and the European Network for the Study of Adrenal Tumors (ENSAT) recommend it in ACC patients at high risk of recurrence. The palliative use of mitotane for treatment of advanced ACC aims at controlling tumor progression and, when present, hormone secretion. In this clinical setting, mitotane is used in association with chemotherapy to treat the more aggressive forms, while mitotane monotherapy is reserved for less progressive ACC. Many years after its introduction in clinical practice, there are still uncertainties surrounding the use of this old drug and the derived benefits. Moreover, physicians who use mitotane should recognize and manage the systemic effects of the drug that need a complex supporting therapy.

Human cytochrome P450 enzymes 5-51 as targets of drugs and natural and environmental compounds: mechanisms, induction, and inhibition - toxic effects and benefits

Cytochrome P450 (P450, CYP) enzymes have long been of interest due to their roles in the metabolism of drugs, pesticides, pro-carcinogens, and other xenobiotic chemicals. They have also been of interest due to their very critical roles in the biosynthesis and metabolism of steroids, vitamins, and certain eicosanoids. This review covers the 22 (of the total of 57) human P450s in Families 5-51 and their substrate selectivity. Furthermore, included is information and references regarding inducibility, inhibition, and (in some cases) stimulation by chemicals. We update and discuss important aspects of each of these 22 P450s and questions that remain open.

Organotin exposure stimulates steroidogenesis in H295R Cell via cAMP pathway

Organotin compounds (OTs) are used in a range of industrial products, such as antifouling paints, agricultural pesticides and stabilizers. Owing to potential endocrine-disrupting effects, human exposure to such compounds is a concern. Nevertheless, little is known about the adverse effect of OTs on adrenocortical function in organisms. In this study, the human adrenocortical carcinoma cell (H295R) model was used to investigate effects of OTs on steroidogenesis and potential causes for such endocrine disruption was examined. H295R cells were exposed to several commonly used OTs, including triphenyltin (TPT), tributyltin (TBT), dibutyltin (DBT), and monobutyltin (MBT), and the production level of steroid hormones were quantified. TPT and TBT decreased the production levels of 17β-estradiol, aldosterone, and cortisol, but increased that of testosterone. Furthermore, the expression levels of ten major steroidogenic genes (HMGR, StAR, CYP11A1, 3βHSD2, CYP17, CYP19A1, CYP21, CYP11B1, CYP11B2, and 17βHSD) were examined and both up-regulation of CYP11B2 and down-regulation of StAR, 3βHSD2, CYP19A1, CYP21 and CYP11B1 by TPT and TBT were observed. Intracellular levels of ATP and cyclic adenosine monophosphate (cAMP) and the activity of adenylate cyclase (AC) decreased in the H295R cells treated with TPT and TBT. No obvious changes in H295R were found with the treatment of DBT and MBT. These results suggest that OTs may stimulate steroidogenesis in vitro via inhibition of cAMP signaling pathway.

CYP11B1 has no role in mitotane action and metabolism in adrenocortical carcinoma cells

Mitotane is the reference drug for adrenocortical carcinoma (ACC) and the metabolic activation of the drug is considered as essential for its activity. The aim of this study was to assess the role of CYP11B1 on mitotane action and metabolism in H295R ACC cells to understand whether this enzyme may influence mitotane action. The simultaneous incubation with mitotane and metyrapone, an adrenolytic molecule targeting 11-beta-hydroxylase, did not influence mitotane-mediated cytotoxic effect and metabolism in H295R ACC cells. CYP11B1 silencing confirmed the lack of a significant metyrapone effect on mitotane action. The present findings do not support the view that CYP11B1 catalyzes a crucial step in the metabolic activation of mitotane and that CYP11B1 confers the adrenal specificity to mitotane.

New insights and future perspectives in the therapeutic strategy of adrenocortical carcinoma (Review)

Adrenocortical carcinoma (ACC) is a rare endocrine malignancy with an incidence ranging from 0.7 to 2.0 cases/million people per year. Hypercortisolism represents the most common clinical presentation in many patients although, less frequently, some ACC secreting androgens and estrogens are even more pathognomonic compared to cortisol secretion. Currently, radical surgery, when feasible, is still the only curative therapy. Mitotane, an adrenolytic drug, is used in the adjuvant setting and in combination with chemotherapy drugs in metastatic disease. The use of radiotherapy remains controversial, being indicated only in selected cases. New targeted therapies, such as insulin growth factor-1 (IGF-1), mammalian-target of rapamycin (m-TOR), vascular endothelial growth factor (VEGF) inhibitors and others, have recently been investigated with disappointing clinical results. The partial effectiveness of current treatments mandates the need for new therapeutic strategies against this tumor.

Rapid and Complete Remission of Metastatic Adrenocortical Carcinoma Persisting 10 Years After Treatment With Mitotane Monotherapy: Case Report and Review of the Literature

Mitotane has been used for more than 5 decades as therapy for adrenocortical carcinoma (ACC). However its mechanism of action and the extent of tumor response remain incompletely understood. To date no cases of rapid and complete remission of metastatic ACC with mitotane monotherapy has been reported. A 52-year-old French Canadian man presented with metastatic disease 2 years following a right adrenalectomy for stage III nonsecreting ACC. He was started on mitotane which was well tolerated despite rapid escalation of the dose. The patient course was exceptional as he responded to mitotane monotherapy after only few months of treatment. Initiation of chemotherapy was not needed and he remained disease-free with good quality of life on low maintenance dose of mitotane during the following 10 years. A germline heterozygous TP53 exon 4 polymorphism c.215C>G (p. Pro72Arg) was found. Immunohistochemical stainings for IGF-2 and cytoplasmic β-catenin were positive. Advanced ACC is an aggressive disease with poor prognosis and the current therapeutic options remain limited. These findings suggest that mitotane is a good option for the treatment of metastatic ACC and might result in rapid complete remission in selected patients.

High risk of adrenal toxicity of N1-desoxy quinoxaline 1,4-dioxide derivatives and the protection of oligomeric proanthocyanidins (OPC) in the inhibition of the expression of aldosterone synthetase in H295R cells

Quinoxaline 1,4-dioxide derivatives (QdNOs) with a wide range of biological activities are used in animal husbandry worldwide. It was found that QdNOs significantly inhibited the gene expression of CYP11B1 and CYP11B2, the key aldosterone synthases, and thus reduced aldosterone levels. However, whether the metabolites of QdNOs have potential adrenal toxicity and the role of oxidative stress in the adrenal toxicity of QdNOs remains unclear. The relatively new QdNOs, cyadox (CYA), mequindox (MEQ), quinocetone (QCT) and their metabolites, were selected for elucidation of their toxic mechanisms in H295R cells. Interestingly, the results showed that the main toxic metabolites of QCT, MEQ, and CYA were their N1-desoxy metabolites, which were more harmful than other metabolites and evoked dose and time-dependent cell damage on adrenal cells and inhibited aldosterone production. Gene and protein expression of CYP11B1 and CYP11B2 and mRNA expression of transcription factors, such as NURR1, NGFIB, CREB, SF-1, and ATF-1, were down regulated by N1-desoxy QdNOs. The natural inhibitors of oxidant stress, oligomeric proanthocyanidins (OPC), could upregulate the expression of diverse transcription factors, including CYP11B1 and CYP11B2, and elevated aldosterone levels to reduce adrenal toxicity. This study demonstrated for the first time that N1-desoxy QdNOs have the potential to be the major toxic metabolites in adrenal toxicity, which may shed new light on the adrenal toxicity of these fascinating compounds and help to provide a basic foundation for the formulation of safety controls for animal products and the design of new QdNOs with less harmful effects.

Effects of adrenolytic mitotane on drug elimination pathways assessed in vitro

Mitotane (1,1-dichloro-2-(o-chlorophenyl)-2-(p-chlorophenyl)ethane, o,p'-DDD) represents one of the most active drugs for the treatment of adrenocortical carcinoma. Its metabolites 1,1-(o,p'-dichlorodiphenyl) acetic acid (=o,p'-DDA) and 1,1-(o,p'-dichlorodiphenyl)-2,2 dichloroethene (=o,p'-DDE) partly contribute to its pharmacological effects. Because mitotane has a narrow therapeutic index and causes pharmacokinetic drug-drug interactions, knowledge about these compounds' effects on drug metabolizing and transporting proteins is crucial. Using quantitative real-time polymerase chain reaction, our study confirmed the strong inducing effects of o,p'-DDD on mRNA expression of cytochrome P450 3A4 (CYP3A4, 30-fold) and demonstrated that other enzymes and transporters are also induced (e.g., CYP1A2, 8.4-fold; ABCG2 (encoding breast resistance cancer protein, BCRP), 4.2-fold; ABCB1 (encoding P-glycoprotein, P-gp) 3.4-fold). P-gp induction was confirmed at the protein level. o,p'-DDE revealed a similar induction profile, however, with less potency and o,p'-DDA had only minor effects. Reporter gene assays clearly confirmed o,p'-DDD to be a PXR activator and for the first time demonstrated that o,p'-DDE and o,p'-DDA also activate PXR albeit with lower potency. Using isolated, recombinant CYP enzymes, o,p'-DDD and o,p'-DDE were shown to strongly inhibit CYP2C19 (IC50 = 0.05 and 0.09 µM). o,p'-DDA exhibited only minor inhibitory effects. In addition, o,p'-DDD, o,p'-DDE, and o,p'-DDA are demonstrated to be neither substrates nor inhibitors of BCRP or P-gp function. In summary, o,p'-DDD and o,p'-DDE might be potential perpetrators in pharmacokinetic drug-drug interactions through induction of drug-metabolizing enzymes or drug transporters and by potent inhibition of CYP2C19. In tumors over-expressing BCRP or P-gp, o,p'-DDD and its metabolites should retain their efficacy due to a lack of substrate characteristics.

RRM1 modulates mitotane activity in adrenal cancer cells interfering with its metabolization

The anti-proliferative activity of mitotane (o,p'DDD) in adrenocortical cancer is mediated by its metabolites o,p'DDE and o,p'DDA. We previously demonstrated a functional link between ribonucleotide reductase M1(RRM1) expression and o,p'DDD activity, but the mechanism is unknown. In this study we assessed the impact of RRM1 on the bioavailability and cytotoxic activity of o,p'DDD, o,p'DDE and o,p'DDA in SW13 and H295R cells. In H295R cells, mitotane and its metabolites showed a similar cytotoxicity and RRM1 expression was not influenced by any drug. In SW13 cells, o,p'DDA only showed a cytotoxic activity and did not modify RRM1 expression, whereas the lack of sensitivity to o,p'DDE was associated to RRM1 gene up-modulation, as already demonstrated for o,p'DDD. RRM1 silencing in SW13 cells increased the intracellular transformation of mitotane into o,p'DDE and o,p'DDA. These data demonstrate that RRM1 gene interferes with mitotane metabolism in adrenocortical cancer cells, as a possible mechanisms of drug resistance.

Practical treatment using mitotane for adrenocortical carcinoma

PURPOSE OF REVIEW

Description of novel findings about the mechanism of action of mitotane and its activity as an adjunctive postoperative measure, or for treatment of advanced adrenocortical carcinoma.

RECENT FINDINGS

Several in-vitro studies have shown that mitotane suppresses gene transcription of different enzymatic steps of the steroidogenetic pathway. Moreover, mitotane induces CYP3A4 expression, thus accelerating the metabolic clearance of a variety of drugs including steroids. Retrospective studies provided evidence that adjunctive mitotane can prolong recurrence-free survival of treated patients. The concept of a therapeutic window of mitotane plasma concentrations was confirmed also for adjunctive treatment, but the relationship between mitotane concentration and given dose is loose. Genetic variability of the P450-dependent enzymes metabolizing mitotane may explain individual differences.

SUMMARY

Mitotane concentration of 14-20  mg/l should be reached and maintained during treatment also in an adjunctive setting. In advanced adrenocortical carcinoma, a high-dose starting regimen should be employed when mitotane is used as monotherapy. The combination of mitotane with other drugs should consider the possibility of pharmacologic interactions due to mitotane-induced activation of drug metabolism. This concept applies also to steroid replacement in mitotane-treated patients, who need higher doses to adjust for increased steroid metabolism.

In vitro exposure of Leydig cells to an environmentally relevant mixture of organochlorines represses early steps of steroidogenesis

Leydig cell steroidogenesis is mainly regulated by LH via increased cAMP production leading to STAR protein activation. STAR is essential for cholesterol shuttling inside mitochondria where steroidogenesis is initiated. Accumulating evidence suggest that persistent organochlorine compounds disrupt testicular function, but the mechanism of action remains poorly characterized. Here we report that in vitro exposure of MA-10 and MLTC-1 Leydig cells to an environmentally relevant mixture of 15 organochlorines impairs steroidogenesis. While having no effect on cell viability and basal steroid production, the organochlorine mixture caused a 50% decrease in cAMP-induced progesterone production. The mixture also reduced cAMP-induced 30 kDa STAR protein by 50% while having no effect on basal STAR protein. Basal or cAMP-induced Star mRNA levels and promoter activity were unaffected by the mixture, indicating that the organochlorine mixture acted at the translational/posttranslational level. Further supporting this is the fact that in COS-7 cells overexpressing STAR, the organochlorine mixture caused a decrease in the 30 kDa form of STAR and an accumulation of the 37 kDa forms. In addition to STAR, we found that the organochlorine mixture also decreases the levels of CYP11A1 and ADXR, two proteins essential for the conversion of cholesterol into pregnenolone. In conclusion, our data show that organochlorine exposure disrupts Leydig cell function by targeting different components of the steroidogenic pathway.

Morphofunctional effects of mitotane on mitochondria in human adrenocortical cancer cells

At present, mitotane (MTT) represents the first-line pharmacological approach for the treatment of advanced adrenocortical carcinoma (ACC). Despite clear evidence that the drug can reduce the clinical signs of steroid excess in secreting ACC, the mechanism mediating the possible toxic effect of MTT on tumor cells still remains obscure. This study investigated the intracellular events underlying the toxic effect of MTT by studying qualitative and quantitative alterations in mitochondrial morphology and functions in human adrenocortical cancer cell lines, H295R and SW13. Increasing concentrations of MTT resulted in rapid intracellular accumulation and conversion of the drug. Cytostatic and cytotoxic effects were evident at doses corresponding to the therapeutic window (30-50 μM) through an apoptotic mechanism involving caspase 3/7. Electron microscopic analysis of cell mitochondria displayed MTT-induced dose- and time-dependent alterations in the morphology of the organelle. These alterations were characterized by a marked swelling and a decrease in the number of respiratory cristae, accompanied by a significant depolarization of the mitochondrial membrane potential, finally leading to the disruption of the organelle. A drastic reduction of oxygen consumption was observed due to mitochondrial membrane damage, which was accompanied by a decrease in the levels of VDAC1 integral membrane channel. These findings contribute to better understand the intracellular mechanism of action of MTT in ACC cells, showing that its cytotoxic effect seems to be mainly mediated by an apoptotic process activated by the disruption of mitochondria.

Interferon-β is a potent inhibitor of cell growth and cortisol production in vitro and sensitizes human adrenocortical carcinoma cells to mitotane

Adrenocortical carcinoma (ACC) is an aggressive tumor with very poor prognosis. Novel medical treatment opportunities are required. We investigated the effects of interferon-β (IFN-β), alone or in combination with mitotane, on cell growth and cortisol secretion in primary cultures of 13 human ACCs, three adrenal hyperplasias, three adrenal adenomas, and in two ACC cell lines. Moreover, the interrelationship between the effects of IGF2 and IFN-β was evaluated. Mitotane inhibited cell total DNA content/well (representing cell number) in 7/11 (IC50: 38±9.2 μM) and cortisol secretion in 5/5 ACC cultures (IC50: 4.5±0.1 μM). IFN-β reduced cell number in 10/11 (IC50: 83±18 IU/ml) and cortisol secretion in 5/5 ACC cultures (IC50: 7.3±1.5 IU/ml). The effect of IFN-β on cell number included the induction of apoptosis. IFN-β strongly inhibited mRNA expression of STAR, CYP11A1, CYP17A1, and CYP11B1. Mitotane and IFN-β induced an additive inhibitory effect on cell number and cortisol secretion. IGF2 (10 nM) inhibited apoptosis and increased cell number and cortisol secretion. These effects were counteracted by IFN-β treatment. Finally, IFN-β inhibited IGF2 secretion and mRNA expression. In conclusion, IFN-β is a potent inhibitor of ACC cell growth in human primary ACC cultures, partially mediated by an inhibition of the effects of IGF2, as well as its production. The increased sensitivity of ACC cells to mitotane induced by treatment with IFN-β may open the opportunity for combined treatment regimens with lower mitotane doses. The inhibition of the expression of steroidogenic enzymes by IFN-β is a novel mechanism that may explain its inhibitory effect on cortisol production.

Mitotane alters mitochondrial respiratory chain activity by inducing cytochrome c oxidase defect in human adrenocortical cells

Mitotane, 1,1-dichloro-2-(o-chlorophenyl)-2-(p-chlorophenyl)ethane is the most effective medical therapy for adrenocortical carcinoma, but its molecular mechanism of action remains poorly understood. Although mitotane is known to have mitochondrial (mt) effects, a direct link to mt dysfunction has never been established. We examined the functional consequences of mitotane exposure on proliferation, steroidogenesis, and mt respiratory chain, biogenesis and morphology, in two human adrenocortical cell lines, the steroid-secreting H295R line and the non-secreting SW13 line. Mitotane inhibited cell proliferation in a dose- and a time-dependent manner. At the concentration of 50 μM (14 mg/l), which corresponds to the threshold for therapeutic efficacy, mitotane drastically reduced cortisol and 17-hydroxyprogesterone secretions by 70%. This was accompanied by significant decreases in the expression of genes encoding mt proteins involved in steroidogenesis (STAR, CYP11B1, and CYP11B2). In both H295R and SW13 cells, 50 μM mitotane significantly inhibited (50%) the maximum velocity of the activity of the respiratory chain complex IV (cytochrome c oxidase (COX)). This effect was associated with a drastic reduction in steady-state levels of the whole COX complex as revealed by blue native PAGE and reduced mRNA expression of both mtDNA-encoded COX2 (MT-CO2) and nuclear DNA-encoded COX4 (COX4I1) subunits. In contrast, the activity and expression of respiratory chain complexes II and III were unaffected by mitotane treatment. Lastly, mitotane exposure enhanced mt biogenesis (increase in mtDNA content and PGC1α (PPARGC1A) expression) and triggered fragmentation of the mt network. Altogether, our results provide first evidence that mitotane induced a mt respiratory chain defect in human adrenocortical cells.

Evaluation of the diagnostic criteria for Cushing's disease in Japan

Adrenocorticotropic hormone (ACTH)-dependent Cushing's syndrome is caused by an ACTH-producing tumor, as is the case with Cushing's disease and ectopic ACTH syndrome (EAS). Diagnosis and differential diagnosis of Cushing's disease from EAS in ACTH-dependent Cushing's syndrome are thus challenging problems in clinical endocrinology. The diagnostic criteria for Cushing's disease in Japan, established by the working group of the Japan Ministry of Health, Labour and Welfare, were originally reported in 2003 and revised in 2007 and 2010. In addition, criteria for subclinical Cushing's disease were established in Japan in 2010. In this review, we evaluate the usefulness and accuracy of the most recent diagnostic criteria. Previous data suggest that as an initial test of Cushing's syndrome, 0.5 mg dexamethasone is more sensitive than 1 mg in the overnight dexamethasone suppression test (DST). Here, we recommend 0.5 mg plus a plasma cortisol cut-off level of 3 µg/dL as a suitable low-dose overnight DST for screening of all cases of ACTH-dependent Cushing's syndrome in Japan. Recently, standardization of cortisol measurements by the ID-LC/MS/MS method using seven assay kits with standard plasma material containing synthetic hydrocortisone-d4 was carried out in Japan. The resulting relative standard deviation was within 10%. The cut-off value remains valid even after standardization of plasma cortisol measurements. Although the recent diagnostic criteria achieve higher diagnostic specificity, care should be taken since data for Cushing's disease partially overlaps with some cases of EAS. Overall, therefore, this review suggests that the accuracy of each diagnostic test should be considered.

The effect of mitotane on viability, steroidogenesis and gene expression in NCI‑H295R adrenocortical cells

Mitotane, also known as o,p'‑DDD or (RS)‑1‑chl-oro‑2‑[2,2‑dichloro‑1‑(4‑chlorophenyl)‑ethyl]‑benzene, is an adrenal cortex-specific cytotoxic drug used in the therapy of adrenocortical carcinoma (ACC). The drug also inhibits steroidogenesis, however, the mechanisms of its anticancer and antisteroidogenic effects remain unknown. At present, data on the impact of mitotane on cell viability and the regulation of genes encoding proteins associated with steroids synthesis in the adrenal cortex, including cortisol and dehydroepiandrosterone sulfate (DHEAS), are limited and contradictory. In the present study, the effect of 24‑h mitotane treatment on viability of the ACC cell line, NCI‑H295R, was analyzed, identifying a decrease in cell viability and an increase in caspase‑3 and ‑7 activities. Mitotane treatment also led to decreased cortisol and DHEAS concentration in the culture media. Concomitantly, mitotane resulted in decreased mRNA levels of two cytochromes P450 (CYP11A1 and CYP17A1), mRNAs encoding proteins involved in the synthesis of cortisol and DHEAS. Mitotane did not affect mRNA levels of cyclin dependent kinase inhibitor 1A (encoding p21) and MYC (encoding cMyc). cMyc and p21 are key transcription factors associated with cell cycle regulation. However, mitotane inhibited expression of transforming growth factor β1 gene, encoding a potent inhibitor of cell proliferation and steroidogenesis. PRKAR1A, a protein kinase A regulatory subunit, is involved in the activation of steroidogenesis. PRKAR1A mRNA levels were reduced following 24‑h treatment with mitotane. Results indicate that mitotane markedly inhibited expression of genes involved in steroidogenesis, secretion of cortisol and DHEAS. Reduced expression of TGFB1 cannot account fully for the effect of mitotane on CYP11A1 and CYP17A1. We hypothesized that reduced viability of NCI‑H295R cells in the presence of mitotane may be a result of apoptosis triggered by increased caspase‑3 and ‑7 activities. Since p21 and cMyc mRNA levels were stable in the presence of mitotane, the mechanism by which caspase‑3 and ‑7 are induced remains unknown.