Characterization of the mTOR pathway in human normal adrenal and adrenocortical tumors

Mammalian Target of Rapamycin Inhibition Decreases Angiotensin II-Induced Steroidogenesis in HAC15 Human Adrenocortical Carcinoma Cells

BACKGROUND

Mammalian target of rapamycin (mTOR) inhibitors suppress adrenal cortical carcinoma cell proliferation and cortisol production; the relationship between mTOR and aldosterone production has not been examined.

METHODS

HAC15 cells were incubated with an mTOR activator and several inhibitors including AZD8055 (AZD) in the presence and absence of angiotensin II (AngII). The expression of rapamycin-sensitive adapter protein of mTOR (Raptor) and rapamycin-insensitive companion of mTOR (Rictor), adaptor proteins of mTOR complex 1 and 2, respectively, were studied in the HAC15 cells and deleted by CRISPR/gRNA.

RESULTS

The mTOR inhibitors decreased aldosterone induced by AngII. Inhibition of mTOR by AZD significantly suppressed AngII-induced aldosterone and cortisol formation in a dose-dependent manner, whereas the mTOR activator MHY had no effect. AZD did not alter forskolin-induced aldosterone production showing that it is specific to the AngII signaling pathway. AngII-mediated ERK and mTOR activation were suppressed by AZD, along with a concomitant dose-dependent reduction of AngII-induced steroidogenic enzymes including steroidogenic acute regulatory protein, 3β-hydroxysteroid dehydrogenase-type 2, CYP17A1, and aldosterone synthase protein. Furthermore, mTOR components ribosomal protein S6 kinase (P70S6K) and protein kinase B phosphorylation levels were decreased by AZD. As mTOR exerts its main effects by forming complexes with adaptor proteins Raptor and Rictor, the roles of these individual complexes were studied. We found an increase in the phosphorylation of Raptor and Rictor by AngII and that their CRISPR/gRNA-mediated knockdown significantly attenuated AngII-induced aldosterone and cortisol production.

CONCLUSION

mTOR signaling has a critical role in transducing the AngII signal initiating aldosterone and cortisol synthesis in HAC15 cells and that inhibition of mTOR could be a therapeutic option for conditions associated with excessive renin-angiotensin system-mediated steroid synthesis.

Immunohistochemical Analysis of the Metabolic Phenotype of Adrenal Cortical Carcinoma

Metabolic reprogramming is a cellular process contributing to carcinogenesis. However, it remains poorly understood in adrenal cortical carcinoma (ACC), an aggressive malignancy with overall poor prognosis and limited therapeutic options. We characterized the metabolic phenotype of ACC, by examining the immunoprofile of key proteins involved in glucose metabolism, hexokinase (HK1), pyruvate kinase (PKM1, PKM2), succinate dehydrogenase (SDHB), and phospho-S6 ribosomal protein (pS6), in a tissue microarray of 137 adrenal cortical tissue samples. Protein expression was compared between ACC (n = 42), adrenal cortical adenoma (ACA; n = 50), and normal adrenal cortical tissue samples (n = 45). Cytoplasmic expression of HK1 and PKM2 was significantly higher in ACC than in ACA (p < 0.001 and p = 0.014, respectively) or normal adrenal cortical tissue samples (p < 0.001 and p < 0.001, respectively). Expression of HK1 and PKM2 was also higher in ACA than in normal adrenal cortical tissue samples (p < 0.001 and p < 0.001, respectively). PKM1 expression was overall low in ACC, ACA, and normal samples, although expression of PKM1 was higher in ACC than in ACA (p = 0.027). There was no loss of cytoplasmic granular SDHB expression in our cohort of adrenal cortical tumors, and cytoplasmic expression of pS6 was lower in ACC than in ACA (p = 0.003) or normal adrenal cortical tissue samples (p = 0.008). Significantly, HK1 expression correlated with pyruvate kinase isoform (PKM2 and PKM1) expression (p < 0.001 and p = 0.007, respectively). Although functional validation was not performed, this study provides further evidence that metabolic reprogramming and altered glucose metabolism may occur in a subset of ACC through overexpression of intracellular glycolytic enzymes, notably HK1 and PKM2. The possibility of utilizing the reprogrammed glucose metabolism in ACC for novel therapeutic strategies should be explored in future studies.

IGF2 role in adrenocortical carcinoma biology

PURPOSE

Clinical outcomes of adrenocortical carcinomas (ACC) could be improved by using novel treatment targets based on the recent advances of tumor biology knowledge. Insulin-like growth factor 2 (IGF2) protein expression is usually 8-80 fold higher in ACC when compared to normal adrenal glands (N-AG) or adrenocortical adenomas (ACA), despite the fact that the biological features of high vs. low IGF2 expressing ACC have not yet been well characterized. Our goal was to understand the IGF2 role in ACC biology by focusing in several cancer hallmarks, including cell proliferation, viability, invasion, and metabolism.

METHODS

IGF2 immunohistochemistry expression was evaluated in ACC (n = 13), non-functioning adrenocortical adenoma (ACAn) (n = 14), and N-AG (n = 9). The effects of IGF2 (50, 100 ng/mL) in cell proliferation, viability, invasion, and metabolism, as well as in MAPK/ERK and mTOR pathways activation and N-cadherin expression, were evaluated in the ACC human cell line H295R.

RESULTS

IGF2 expression was increased in ACC compared to ACAn and N-AG. Exposure to 100 ng/mL of IGF2 increased H295R cell proliferation and viability. mTOR inhibition reverted IGF2 triggered cell proliferation and viability while MEK/MAPK/ERK inhibition only reverted IGF2 effects on cell proliferation. IGF2 at a 50 ng/mL concentration increased the glycolytic flux and decreased glutamine consumption.

CONCLUSIONS

IGF2 is an excellent marker to differentiate ACC from ACAn. In addition, IGF2 was demonstrated to influence adrenocortical cancer cell proliferation, metabolism, and viability, but not the cell invasion. These data support that different IGF2 concentrations in ACC can be responsible for different biological behaviors of ACC.

Treatment of Primary Aldosteronism With mTORC1 Inhibitors

CONTEXT

Mammalian target of rapamycin complex 1 (mTORC1) activity is often increased in the adrenal cortex of patients with primary aldosteronism (PA), and mTORC1 inhibition decreases aldosterone production in adrenocortical cells, suggesting the mTORC1 pathway as a target for treatment of PA.

OBJECTIVE

To investigate the effect of mTORC1 inhibition on adrenal steroid hormones and hemodynamic parameters in mice and in patients with PA.

DESIGN

(i) Plasma aldosterone, corticosterone, and angiotensin II (Ang II) were measured in mice treated for 24 hours with vehicle or rapamycin. (ii) Plasma aldosterone levels after a saline infusion test, plasma renin, and 24-hour urine steroid hormone metabolome and hemodynamic parameters were measured during an open-label study in 12 patients with PA, before and after 2 weeks of treatment with everolimus and after a 2-week washout.

MAIN OUTCOME MEASURES

(i) Change in plasma aldosterone levels. (ii) Change in other steroid hormones, renin, Ang II, and hemodynamic parameters.

RESULTS

Treatment of mice with rapamycin significantly decreased plasma aldosterone levels (P = 0.007). Overall, treatment of PA patients with everolimus significantly decreased blood pressure (P < 0.05) and increased renin levels (P = 0.001) but did not decrease aldosterone levels significantly. However, prominent reduction of aldosterone levels upon everolimus treatment was observed in four patients.

CONCLUSION

In mice, mTORC1 inhibition was associated with reduced plasma aldosterone levels. In patients with PA, mTORC1 inhibition was associated with improved blood pressure and renin suppression. In addition, mTORC1 inhibition appeared to reduce plasma aldosterone in a subset of patients.

The role of mTOR pathway as target for treatment in adrenocortical cancer

Adrenocortical carcinomas (ACCs) are rare tumors with scant treatment options for which new treatments are required. The mTOR pathway mediates the intracellular signals of several growth factors, including the insulin-like growth factors (IGFs), and therefore represents a potential attractive pathway for the treatment of several malignancies including ACCs. Several mTOR inhibitors, including sirolimus, temsirolimus and everolimus, have been clinically developed. This review summarizes the results of the studies evaluating the expression of the mTOR pathway components in ACCs, the effects of the mTOR inhibitors alone or in combination with other drugs in preclinical models of ACCs and the early experience with the use of these compounds in the clinical setting. The mTOR pathway seems a potential target for treatment of patients with ACC, but further investigation is still required to define the potential role of mTOR inhibitors alone or in combination with other drugs in the treatment of ACC patients.

IGF and mTOR pathway expression and in vitro effects of linsitinib and mTOR inhibitors in adrenocortical cancer

PURPOSE

The IGF and mTOR-pathways are considered as potential targets for therapy in patients with adrenocortical carcinoma (ACC). This study aims to describe the IGF pathway in ACC and to explore the response to the combined treatment with the IGF1R/IR inhibitor linsitinib, and mTOR inhibitors (sirolimus and everolimus) in in vitro models of ACC.

METHODS

The protein expression level of IGF2, IGF1R and IGF2R was evaluated by immunohistochemistry in 17 human ACCs and the mRNA expression level of IGF1, IGF2, IGF1R, IR isoforms A and B, IGF2R, IGF-Binding-Proteins[IGFBP]-1, 2, 3 and 6 was evaluated by RT-qPCR in 12 samples. In H295R and HAC15 ACC cell lines the combined effects of linsitinib and sirolimus or everolimus on cell survival were evaluated.

RESULTS

A high protein expression of IGF2, IGF1R and IGF2R was observed in 82, 65 and 100% of samples, respectively. A high relative expression of IGF2 mRNA was found in the majority of samples. The mRNA levels of the IRA were higher than that of IRB and IGF1R in the majority of samples (75%). Linsitinib inhibits cell growth in the H295R and HAC15 cell lines and, combined with sirolimus or everolimus, linsitinib showed a significant additive effect.

CONCLUSIONS

In addition to IGF2 and IGF1R, ACC express IGF2R, IRA and several IGFBPs, suggesting that the interplay between the different components of the IGF pathway in ACC could be more complex than previously considered. The addition of mTOR inhibitors to linsitinib may have stronger antiproliferative effects than linsitinib alone.

Diagnostic and Prognostic Biomarkers of Adrenal Cortical Carcinoma

The diagnosis of low-grade adrenal cortical carcinoma (ACC) confined to the adrenal gland can be challenging. Although there are diagnostic and prognostic molecular tests for ACC, they remain largely unutilized. We examined the diagnostic and prognostic value of altered reticulin framework and the immunoprofile of biomarkers including IGF-2, proteins involved in cell proliferation and mitotic spindle regulation (Ki67, p53, BUB1B, HURP, NEK2), DNA damage repair (PBK, γ-H2AX), telomere regulation (DAX, ATRX), wnt-signaling pathway (beta-catenin) and PI3K signaling pathway (PTEN, phospho-mTOR) in a tissue microarray of 50 adenomas and 43 carcinomas that were characterized for angioinvasion as defined by strict criteria, Weiss score, and mitotic rate-based tumor grade. IGF-2 and proteins involved in cell proliferation and mitotic spindle regulation (Ki67, p53, BUB1B, HURP, NEK2), DNA damage proteins (PBK, γ-H2AX), regulators of telomeres (DAXX, ATRX), and beta-catenin revealed characteristic expression profiles enabling the distinction of carcinomas from adenomas. Not all biomarkers were informative in all carcinomas. IGF-2 was the most useful biomarker of malignancy irrespective of tumor grade and cytomorphologic features, as juxtanuclear Golgi-pattern IGF-2 reactivity optimized for high specificity was identified in up to 80% of carcinomas and in no adenomas. Loss rather than qualitative alterations of the reticulin framework yielded statistical difference between carcinoma and adenoma. Angioinvasion defined as tumor cells invading through a vessel wall and intravascular tumor cells admixed with thrombus proved to be the best prognostic parameter, predicting adverse outcome in the entire cohort as well as within low-grade ACCs. Low mitotic tumor grade, Weiss score, global loss of DAXX expression, and high phospho-mTOR expression correlated with disease-free survival, but Weiss score and biomarkers failed to predict adverse outcome in low-grade disease. Our results underscore the importance of careful morphologic assessment coupled with ancillary diagnostic and prognostic biomarkers of ACC.

Metformin as a new anti-cancer drug in adrenocortical carcinoma

Adrenocortical carcinoma (ACC) is a rare heterogeneous malignancy with poor prognosis. Since radical surgery is the only available treatment, more specific and effective drugs are urgently required. The anti-diabetic drug metformin has been associated with a decreased cancer prevalence and mortality in several solid tumors, prompting its possible use for ACC treatment.

This paper evaluates the in vitro and in vivo anti-cancer effects of metformin using the ACC cell model H295R.

Metformin treatment significantly reduces cell viability and proliferation in a dose- and time-dependent manner and associates with a significant inhibition of ERK1/2 and mTOR phosphorylation/activation, as well as with stimulation of AMPK activity. Metformin also triggers the apoptotic pathway, shown by the decreased expression of Bcl-2 and HSP27, HSP60 and HSP70, and enhanced membrane exposure of annexin V, resulting in activation of caspase-3 apoptotic effector. Metformin interferes with the proliferative autocrine loop of IGF2/IGF-1R, which supports adrenal cancer growth. Finally, in the ACC xenograft mouse model, obtained by subcutaneous injection of H295R cells, metformin intraperitoneal administration inhibits tumor growth, confirmed by the significant reduction of Ki67%.

Our data suggest that metformin inhibits H295R cell growth both in vitro and in vivo. Further preclinical studies are necessary to validate the potential anti-cancer effect of metformin in patients affected by ACC.

Analysis of 10 Adrenocortical Carcinoma Patients in the Cohort of the Precision Medicine Platform MONDTI

OBJECTIVE

Adrenocortical carcinoma (ACC) is a rare disease with a dismal prognosis. We aimed to evaluate if a personalized medicine approach may be useful for matching patients with ACC to targeted therapies.

METHODS

This is an analysis of 10 molecularly profiled ACCs that were progressing under standard of care treatment. The profile consisted of a 50-gene next-generation sequencing panel, immunohistochemistry (IHC), and fluorescence in situ hybridization for several proteins or chromosomal aberrations.

RESULTS

In 6 (60%) tumor samples, no somatic mutation was detected, while in 3 (30%) tumors 1 mutation was detected and in 1 (10%) tumor 2 mutations were detected. These mutations were CTNNB1 (2 samples), TP53 (1 sample), RB1 (1 sample) and APC (1 sample). Expression of phospho-mTOR and of EGFR was commonly detected by IHC (87.5 and 62.5%). In 4 (50%) samples, IHC revealed a weak expression of progesterone receptor. Less frequent alterations were expression of PDGFR-α, c-KIT, and estrogen receptor, each in 1 case.

CONCLUSIONS

Based on the molecular profile, no recommendation for targeted therapy was made by the multi-disciplinary team. Currently, ACC might not be suitable for a precision medicine approach according to our tests.

The challenge of developmental therapeutics for adrenocortical carcinoma

Adrenocortical carcinoma (ACC) is a rare disease with an estimated incidence of only 0.7 new cases per million per year. Approximately 30-70% of the patients present with advanced disease with very poor prognosis and without effective therapeutic options. In the recent years, unprecedented progresses in cancer biology and genomics have fostered the development of numerous targeted therapies for various malignancies. Immunotherapy has also transformed the treatment landscape of malignancies such as melanoma, among others. However, these advances have not brought meaningful benefits for patients with ACC. Extensive genomic analyses of ACC have revealed numerous signal transduction pathway aberrations (e.g., insulin growth factor receptor and Wnt/β-catenin pathways) that play a central role in pathophysiology. These molecular alterations have been explored as potential therapeutic targets for drug development. This manuscript summarizes recent discoveries in ACC biology, reviews the results of early clinical studies with targeted therapies, and provides the rationale for emerging treatment strategies such as immunotherapy.

Molecular targeted therapies in adrenal, pituitary and parathyroid malignancies

Tumourigenesis is a relatively common event in endocrine tissues. Currently, specific guidelines have been developed for common malignant endocrine tumours, which also incorporate advances in molecular targeted therapies (MTT), as in thyroid cancer and in gastrointestinal neuroendocrine malignancies. However, there is little information regarding the role and efficacy of MTT in the relatively rare malignant endocrine tumours mainly involving the adrenal medulla, adrenal cortex, pituitary, and parathyroid glands. Due to the rarity of these tumours and the lack of prospective studies, current guidelines are mostly based on retrospective data derived from surgical, locoregional and ablative therapies, and studies with systemic chemotherapy. In addition, in many of these malignancies the prognosis remains poor with individual patients responding differently to currently available treatments, necessitating the development of new personalised therapeutic strategies. Recently, major advances in the molecular understanding of endocrine tumours based on genomic, epigenomic, and transcriptome analysis have emerged, resulting in new insights into their pathogenesis and molecular pathology. This in turn has led to the use of novel MTTs in increasing numbers of patients. In this review, we aim to present currently existing and evolving data using MTT in the treatment of adrenal, pituitary and malignant parathyroid tumours, and explore the current utility and effectiveness of such therapies and their future evolution.

Effects of the single and combined treatment with dopamine agonist, somatostatin analog and mTOR inhibitors in a human lung carcinoid cell line: an in vitro study

Somatostatin analogues and mTOR inhibitors have been used as medical therapy in lung carcinoids with variable results. No data are available on dopamine agonists as treatment for lung carcinoids. The main aim of the current study was to evaluate the effect of the combined treatment of somatostatin analogue octreotide and the dopamine agonist cabergoline with mTOR inhibitors in an in vitro model of typical lung carcinoids: the NCI-H727 cell line. In NCI-H727 cell line, reverse transcriptase-quantitative polymerase chain reaction and immunofluorescence were assessed to characterize the expression of the somatostatin receptor 2 and 5, dopamine receptor 2 and mTOR pathway components. Fifteen typical lung carcinoids tissue samples have been used for somatostatin receptor 2, dopamine receptor 2, and the main mTOR pathway component p70S6K expression and localization by immunohistochemistry. Cell viability, fluorescence-activated cell sorting analysis and western blot have been assessed to test the pharmacological effects of octreotide, cabergoline and mTOR inhibitors, and to evaluate the activation of specific cell signaling pathways in NCI-H727 cell line. NCI-H727 cell line expressed somatostatin receptor 2, somatostatin receptor 5 and dopamine receptor 2 and all mTOR pathway components at messenger and protein levels. Somatostatin receptor 2, dopamine receptor 2, and p70S6K (non phosphorylated and phosphorylated) proteins were expressed in most typical lung carcinoids tissue samples. Octreotide and cabergoline did not reduce cell viability as single agents but, when combined with mTOR inhibitors, they potentiate mTOR inhibitors effect after long-term exposure, reducing Akt and ERK phosphorylation, mTOR escape mechanisms, and increasing the expression DNA-damage-inducible transcript 4, an mTOR suppressor. In conclusion, the single use of octreotide and cabergoline is not sufficient to block cell viability but the combined approach of these agents with mTOR inhibitors might reduce the mTOR inhibitors-induced escape mechanisms and/or activate the endogenous mTOR suppressor, potentiating the effect of the mTOR inhibitors in an in vitro model of typical lung carcinoids.

Tissue Expression and Pharmacological In Vitro Analyses of mTOR and SSTR Pathways in Adrenocortical Carcinoma

New therapies for advanced adrenocortical carcinoma (ACC) are urgently needed, as the majority of the patients experience a rapid and inexorable progression despite surgery and adjuvant mitotane. In vitro data suggest that somatostatin receptors (SSTRs) and mTOR pathway might represent reasonable targets for novel therapies, being involved in functionality and growth of ACC cells. However, in vitro analysis of combination treatments targeting both mTOR and SSTR as compared to mitotane are poorly explored in ACC. This study aimed to investigate in vitro the effects on cell growth of pasireotide, everolimus, and mitotane, alone or combined, in the two ACC cell lines H295R and SW13 (mitotane sensitive and resistant, respectively). Moreover, the tissue expression of mTOR pathway molecules and SSTR (types 1-5) was assessed in 58 ACCs. In both cell lines, only everolimus induced a significant inhibition of cell growth. Conversely, the combinations among mitotane, pasireotide, and everolimus produced antagonistic effects on mitotane-induced growth inhibition on H295R cell line. A heterogeneous profile of mTOR-related molecules and SSTR expression was observed in ACC samples, being the mTOR pathway found activated in approximately 30% of cases. In conclusion, our data suggest caution in designing combinations of mitotane with other drugs potentially active in ACC, such as mTOR inhibitors or somatostatin analogs.

P53/Rb inhibition induces metastatic adrenocortical carcinomas in a preclinical transgenic model

Adrenocortical carcinoma (ACC) is a rare cancer with poor prognosis. Pan-genomic analyses identified p53/Rb and WNT/β-catenin signaling pathways as main contributors to the disease. However, isolated β-catenin constitutive activation failed to induce malignant progression in mouse adrenocortical tumors. Therefore, there still was a need for a relevant animal model to study ACC pathogenesis and to test new therapeutic approaches. Here, we have developed a transgenic mice model with adrenocortical specific expression of SV40 large T-antigen (AdTAg mice), to test the oncogenic potential of p53/Rb inhibition in the adrenal gland. All AdTAg mice develop large adrenal carcinomas that eventually metastasize to the liver and lungs, resulting in decreased overall survival. Consistent with ACC in patients, adrenal tumors in AdTAg mice autonomously produce large amounts of glucocorticoids and spontaneously activate WNT/β-catenin signaling pathway during malignant progression. We show that this activation is associated with downregulation of secreted frizzled related proteins (Sfrp) and Znrf3 that act as inhibitors of the WNT signaling. We also show that mTORC1 pathway activation is an early event during neoplasia expansion and further demonstrate that mTORC1 pathway is activated in ACC patients. Preclinical inhibition of mTORC1 activity induces a marked reduction in tumor size, associated with induction of apoptosis and inhibition of proliferation that results in normalization of corticosterone plasma levels in AdTAg mice. Altogether, these data establish AdTAg mice as the first preclinical model for metastatic ACC.

Effect of Orexin-A on Cortisol Secretion in H295R Cells via p70S6K/4EBP1 Signaling Pathway

Orexin-A is a neuropeptide that orchestrates diverse central and peripheral processes. It is now clear that orexin system plays a central role in the regulation of endocrine, paracrine, and neurocrine. It is involved in the regulation of growth hormone, adrenocorticotropic hormone, thyroid, mineralocorticoid, and cortisol secretion. These hormones may also serve as a kind of signal linking energy balance regulation, reproduction, stress response, and cardiovascular regulation. Many studies have demonstrated the ability of orexin-A to regulate adrenocortical cells through the MAPK (mitogen-activated protein kinases) pathway. The aim of our study is to investigate the effect of orexin-A on cortisol secretion via the protein 70 ribosomal protein S6 kinase-1 (p70S6K) and eukaryotic translation initiation factor 4E binding proteins (4EBP1) signaling pathway in adrenocortical cells. We reported the first evidence that orexin-A stimulated p70S6K and 4EBP1 in human H295R adrenocortical cells in a concentration and time-dependent manner. 10(-6) M orexin-A treatment for 1 hour was the most potent. Our results also indicated that p70S6K and 4EBP1 kinases participated in controlling cortisol secretion via OX1 receptor in H295R cells, which implied important role of p70S6K and 4EBP1 kinases in regulating adrenal function induced by orexin-A.

Roles of the pathologist in evaluating surrogate markers for medical therapy in adrenocortical carcinoma

Adrenocortical carcinoma is a rare malignancy. Medical treatment including op'DDD or mitotane with or without platinum-based cytotoxic chemotherapy is frequently administered to the patients in an adjuvant setting following surgery or in advanced disease, because of aggressive clinical behavior in some cases. Potential roles of pathologists in determining the clinical algorithm of medical therapy are histopathological confirmation of adrenocortical carcinoma, both malignant features using the criteria of Weiss and adrenocortical origin applying immunohistochemistry of steroid factor-1 (SF-1); providing the relevant pathological information to determine the precise pathological stage in individual patients; and providing the accurate Ki67 labeling index of the patients. There are no established pathological surrogate markers for response to mitotane or op' DDD therapy available at this juncture but as in other malignancies, Ki67 LI could provide information as to the potential clinical response to platinum-based cytotoxic chemotherapy. Epidermal growth factor receptor (EGFR) is significantly overexpressed in adrenocortical carcinoma but the absence of gene mutations could limit the therapeutic application of anti-EGFR antibody and/or EGFR tyrosine kinase inhibitor in the patients.