Germline mutations in the aryl hydrocarbon receptor interacting protein (AIP) gene were recently observed in patients with pituitary adenoma predisposition (PAP). Though AIP mutation-positive individuals with prolactin-, mixed growth hormone/prolactin-, and ACTH-producing pituitary adenomas as well as non-secreting pituitary adenomas have been reported, most mutation-positive patients have had growth hormone-producing adenomas diagnosed at relatively young age. Pituitary adenomas are also component tumors of some familial endocrine neoplasia syndromes such as multiple endocrine neoplasia type 1 (MEN1) and Carney complex (CNC). Genes underlying MEN1 and CNC are rarely mutated in sporadic pituitary adenomas, but more often in other lesions contributing to these two syndromes. Thus far, the occurrence of somatic AIP mutations has not been studied in endocrine tumors other than pituitary adenomas. Here, we have analyzed 32 pituitary adenomas and 79 other tumors of the endocrine system for somatic AIP mutations by direct sequencing. No somatic mutations were identified. However, two out of nine patients with prolactin-producing adenoma were shown to harbor a Finnish founder mutation (Q14X) with a complete loss of the wild-type allele in the tumors. These results are in agreement with previous studies in that prolactin-producing adenomas are component tumors in PAP. The data also support the previous finding that somatic AIP mutations are not common in pituitary adenomas and suggest that such mutations are rare in other endocrine tumors as well.
A Raitila, M Georgitsi, A Karhu, K Tuppurainen, M J Mäkinen, K Birkenkamp-Demtröder, K Salmenkivi, T F Ørntoft, J Arola, V Launonen, P Vahteristo, and L A Aaltonen
C Schaaf, B Shan, M Buchfelder, M Losa, J Kreutzer, W Rachinger, G K Stalla, T Schilling, E Arzt, M J Perone, and U Renner
Curcumin (diferuloylmethane) is the active ingredient of the spice plant Curcuma longa and has been shown to act anti-tumorigenic in different types of tumours. Therefore, we have studied its effect in pituitary tumour cell lines and adenomas. Proliferation of lactosomatotroph GH3 and somatotroph MtT/S rat pituitary cells as well as of corticotroph AtT20 mouse pituitary cells was inhibited by curcumin in monolayer cell culture and in colony formation assay in soft agar. Fluorescence-activated cell sorting (FACS) analysis demonstrated curcumin-induced cell cycle arrest at G2/M. Analysis of cell cycle proteins by immunoblotting showed reduction in cyclin D1, cyclin-dependent kinase 4 and no change in p27kip. FACS analysis with Annexin V-FITC/7-aminoactinomycin D staining demonstrated curcumin-induced early apoptosis after 3, 6, 12 and 24 h treatment and nearly no necrosis. Induction of DNA fragmentation, reduction of Bcl-2 and enhancement of cleaved caspase-3 further confirmed induction of apoptosis by curcumin. Growth of GH3 tumours in athymic nude mice was suppressed by curcumin in vivo. In endocrine pituitary tumour cell lines, GH, ACTH and prolactin production were inhibited by curcumin. Studies in 25 human pituitary adenoma cell cultures have confirmed the anti-tumorigenic and hormone-suppressive effects of curcumin. Altogether, the results described in this report suggest this natural compound as a good candidate for therapeutic use on pituitary tumours.
K Revill, K J Dudley, R N Clayton, A M McNicol, and W E Farrell
The imprinted gene, neuronatin (NNAT), is one of the most abundant transcripts in the pituitary and is thought to be involved in the development and maturation of this gland. In a recent whole-genome approach, exploiting a pituitary tumour cell line, we identified hypermethylation associated loss of NNAT. In this report, we determined the expression pattern of NNAT in individual cell types of the normal gland and within each of the different pituitary adenoma subtypes. In addition, we determined associations between expression and CpG island methylation and used colony forming efficiency assays (CFE) to gain further insight into the tumour-suppressor function of this gene. Immunohistochemical (IHC) co-localization studies of normal pituitaries showed that each of the hormone secreting cells (GH, PRL, ACTH, FSH and TSH) expressed NNAT. However, 33 out of 47 adenomas comprising, 11 somatotrophinomas, 10 prolactinomas, 12 corticotrophinomas and 14 non-functioning tumours, irrespective of subtype failed to express either NNAT transcript or protein as determined by quantitative real-time RT-PCR and IHC respectively. In normal pituitaries and adenomas that expressed NNAT the promoter-associated CpG island showed characteristics of an imprinted gene where ∼50% of molecules were densely methylated. However, in the majority of adenomas that showed loss or significantly reduced expression of NNAT, relative to normal pituitaries, the gene-associated CpG island showed significantly increased methylation. Induced expression of NNAT in transfected AtT-20 cells significantly reduced CFE. Collectively, these findings point to an important role for NNAT in the pituitary and perhaps tumour development in this gland.
V V Vax, M Gueorguiev, I I Dedov, A B Grossman, and M Korbonits
The oncogenes and/or tumour suppressor genes which may be involved in the transformation process for the vast majority of pituitary tumours remain unknown. There is substantial evidence for derangement of cell cycle control in such tumours, but cell cycle protein mutations identified in other human malignancies are restricted to only a very small subset of sporadic pituitary neoplasms. Kr√ºppel-like factors are DNA-binding transcriptional regulators with diverse effects including the upregulation of the cell cycle protein p21(WAF1/CIP1). It has been reported that the Kr√ºppel-like transcription factor 6 (KLF6) gene is mutated in a proportion (15-55%) of human prostate cancers, and more recent data are emerging regarding mutated KLF6 in nasopharyngeal carcinomas, astrocytoid gliomas and colorectal cancer. We therefore speculated that other tumours such as pituitary adenomas might also harbour such mutations that may be involved in the control of cell proliferation in the pituitary. The aim of the current study was thus to analyse the KLF6 gene for mutations in sporadic pituitary tumours. We analysed 60 pituitary adenomas (15 GH-, four ACTH-, two PRL-secreting and 39 non-functioning) with direct sequence analysis of exons 2 and 3 of the KLF6 gene, the region where most of the previously described mutations are located. Three non-functioning pituitary adenomas of the 60 pituitary tumours (5%) had two identical sequence changes in exon 2 (missense mutation Val165Met, 523G-->A and a silent substitution in Ser77Ser codon 261C-->T). Analysis of genomic DNA extracted from peripheral lymphocytes in one patient confirmed these changes to be present in the germline and they therefore probably represent polymorphisms, although we cannot exclude the possibility that these are predisposing germline mutations. We conclude that mutations of the KLF6 gene are unlikely to play an important role in sporadic pituitary tumorigenesis.
D Dworakowska, E Wlodek, C A Leontiou, S Igreja, M Cakir, M Teng, N Prodromou, M I Góth, S Grozinsky-Glasberg, M Gueorguiev, B Kola, M Korbonits, and A B Grossman
Raf/MEK/ERK and phosphatidylinositol 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) cascades are key signalling pathways interacting with each other to regulate cell growth and tumourigenesis. We have previously shown B-Raf and Akt overexpression and/or overactivation in pituitary adenomas. The aim of this study is to assess the expression of their downstream components (MEK1/2, ERK1/2, mTOR, TSC2, p70S6K) and effectors (c-MYC and CYCLIN D1). We studied tissue from 16 non-functioning pituitary adenomas (NFPAs), six GH-omas, six prolactinomas and six ACTH-omas, all collected at transsphenoidal surgery; 16 normal autopsy pituitaries were used as controls. The expression of phospho and total protein was assessed with western immunoblotting, and the mRNA expression with quantitative RT-PCR. The expression of pSer217/221 MEK1/2 and pThr183 ERK1/2 (but not total MEK1/2 or ERK1/2) was significantly higher in all tumour subtypes in comparison to normal pituitaries. There was no difference in the expression of phosphorylated/total mTOR, TSC2 or p70S6K between pituitary adenomas and controls. Neither c-MYC phosphorylation at Ser 62 nor total c-MYC was changed in the tumours. However, c-MYC phosphorylation at Thr58/Ser62 (a response target for Akt) was decreased in all tumour types. CYCLIN D1 expression was higher only in NFPAs. The mRNA expression of MEK1, MEK2, ERK1, ERK2, c-MYC and CCND1 was similar in all groups. Our data indicate that in pituitary adenomas both the Raf/MEK/ERK and PI3K/Akt/mTOR pathways are upregulated in their initial cascade, implicating a pro-proliferative signal derangement upstream to their point of convergence. However, we speculate that other processes, such as senescence, attenuate the changes downstream in these benign tumours.
Thomas G Papathomas, Lindsey Oudijk, Ellen C Zwarthoff, Edward Post, Floor A Duijkers, Max M van Noesel, Leo J Hofland, Patrick J Pollard, Eamonn R Maher, David F Restuccia, Richard A Feelders, Gaston J H Franssen, Henri J Timmers, Stefan Sleijfer, Wouter W de Herder, Ronald R de Krijger, Winand N M Dinjens, and Esther Korpershoek
Hotspot mutations in the promoter of the telomerase reverse transcriptase (TERT) gene have been recently reported in human cancers and proposed as a novel mechanism of telomerase activation. To explore TERT promoter mutations in tumors originating from the adrenal gland and extra-adrenal paraganglia, a set of 253 tumors (38 adrenocortical carcinomas (ACCs), 127 pheochromocytomas (PCCs), 18 extra-adrenal paragangliomas (ea PGLs), 37 head and neck PGLs (HN PGLs), and 33 peripheral neuroblastic tumors) was selected along with 16 human neuroblastoma (NBL) and two ACC cell lines to assess TERT promoter mutations by the Sanger sequencing method. All mutations detected were confirmed by a SNaPshot assay. Additionally, 36 gastrointestinal stromal tumors (GISTs) were added to explore an association between TERT promoter mutations and SDH deficiency. TERT promoter mutations were found in seven out of 289 tumors and in three out of 18 human cell lines; four C228T mutations in 38 ACCs (10.5%), two C228T mutations in 18 ea PGLs (11.1%), one C250T mutation in 36 GISTs (2.8%), and three C228T mutations in 16 human NBL cell lines (18.75%). No mutation was detected in PCCs, HN PGLs, neuroblastic tumors as well as ACC cell lines. TERT promoter mutations preferentially occurred in a SDH-deficient setting (P=0.01) being present in three out of 47 (6.4%) SDH-deficient tumors vs zero out of 171 (0%) SDH-intact tumors. We conclude that TERT promoter mutations occur in ACCs and ea PGLs. In addition, preliminary evidence indicates a potential association with the acquisition of TERT promoter mutations in SDH-deficient tumors.
Anna Angelousi, Eva Kassi, Narjes Ansari-Nasiri, Harpal Randeva, Gregory Kaltsas, and George Chrousos
Circadian rhythms at a central and peripheral level are operated by transcriptional/translational feedback loops involving a set of genes called ‘clock genes’ that have been implicated in the development of several diseases, including malignancies. Dysregulation of the Clock system can influence cancer susceptibility by regulating DNA damage and repair mechanisms, as well as apoptosis. A number of oncogenic pathways can be dysregulated via clock genes’ epigenetic alterations, including hypermethylation of clock genes’ promoters or variants of clock genes. Clock gene disruption has been studied in breast, lung and prostate cancer, and haematological malignancies. However, it is still not entirely clear whether clock gene disruption is the cause or the consequence of tumourigenesis and data in endocrine neoplasms are scarce. Recent findings suggest that clock genes are implicated in benign and malignant adrenocortical neoplasias. They have been also associated with follicular and papillary thyroid carcinomas and parathyroid adenomas, as well as pituitary adenomas and craniopharyngiomas. Dysregulation of clock genes is also encountered in ovarian and testicular tumours and may also be related with their susceptibility to chemotherapeutic agents. The most common clock genes that are implicated in endocrine neoplasms are PER1, CRY1; in most cases their expression is downregulated in tumoural compared to normal tissues. Although there is still a lot to be done for the better understanding of the role of clock genes in endocrine tumourigenenesis, existing evidence could guide research and help identify novel therapeutic targets aiming mainly at the peripheral components of the clock gene system.
Susanna Vuorenoja, Bidut Prava Mohanty, Johanna Arola, Ilpo Huhtaniemi, Jorma Toppari, and Nafis A Rahman
Lytic peptide Hecate (23-amino acid (AA)) fused with a 15-AA fragment of human chorionic gonadotropin-β (CG-β), Hecate-CGβ conjugate (H-CGβ-c) selectively binds to and destroys tumor cells expressing LH/chorionic gonadotropin receptor (Lhcgr). Transgenic mice (6.5 month old) expressing SV40 T-antigen under the inhibin-α promoter (inhα/Tag) presenting with Lhcgr expressing adrenal tumors were treated either with H-CGβ-c, GnRH antagonist (GnRH-a), estradiol (E2; only females) or their combinations for 1 month. We expected that GnRH-a or E2 in combination with H-CGβ-c could improve the treatment efficacy especially in females by decreasing circulating LH and eliminating the potential competition of serum LH with the H-CGβ-c. GnRH-a and H-CGβ-c treatments were successful in males (adrenal weights 14±2.8 mg and 60±26 vs 237±59 mg in controls; P<0.05). Histopathologically, GnRH-a apparently destroyed the adrenal parenchyma leaving only the fibrotic capsule with few necrotic foci. In females, H-CGβ-c was totally ineffective, whereas GnRH-a (19±5 mg) or E2 (77±50 mg) significantly reduced the adrenal weights compared with controls (330±70 mg). Adrenal morphometry, cell proliferation markers, post-treatment suppression of serum progesterone, and quantitative RT-PCR of GATA-4, Lhcgr, and GATA-6 further supported the positive outcome. H-CGβ-c selectively killed the Lhcgr expressing tumor cells, whereas GnRH-a blocked tumor progression through gonadotropin suppression, emphasizing the gonadotropin dependency of these adrenocortical tumors. If extrapolated to humans, H-CGβ-c could be considered for the treatment of gonadotropin-dependent adrenal tumors in males, whereas in females gonadotropin suppression, but not H-CGβ-c, would work better.
M Seki, K Nomura, D Hirohara, M Kanazawa, T Sawada, K Takasaki, and H Demura
A 58-year-old man had adrenocortical carcinoma in the right adrenal gland. The tumour secreted excessive cortisol and dehydroepiandrosterone-sulphate (DHEA-S), and had invaded the right hepatic lobe and vena cava. Eleven months after surgical tumour resection, the serum DHEA-S levels again increased. Local tumour recurrence and a metastasis was found in the lung. Eleven months after surgery chemotherapy with mitotane (o,p'-DDD) was initiated. Twelve weeks of mitotane reduced serum DHEA-S levels and caused these tumours to disappear. The patient was then treated with low-dose mitotane (1.5-2.0 g/day) for 2 years. Serum levels of mitotane remained at less than 10 microg/ml. Although such low serum levels of mitotane and delayed initiation of mitotane after surgery have been proposed to weaken the antineoplastic effect of mitotane, the patient had a remission for 2 years. However, there was then local re-recurrence with an increase in serum DHEA-S and death 4 months later. The histological features of neoplastic cells were quite different comparing tumour resected at surgery and tumour at autopsy. The latter had more frequent mitotic nuclei. This tumour was initially sensitive to mitotane, but later became insensitive.
Constanze Hantel, Sara Jung, Thomas Mussack, Martin Reincke, and Felix Beuschlein
Owing to high relapse rates and early metastatic spread, prognosis in adrenocortical carcinoma (ACC) patients remains poor, highlighting the importance of developing new treatment alternatives for them. Recently, polychemotherapy regimens including etoposide, doxorubicin, and cisplatin together with mitotane (EDP-M) have been defined as the standard treatment for late-stage disease patients. Nevertheless, the administration of conventional cytostatic drugs is associated with severe and dose-limiting side effects. In an attempt to optimize existing clinical treatment regimens, in this study, we investigated the therapeutic efficacy of EDP-M in comparison with that of a paclitaxel-modified scheme (paclitaxel, doxorubicin, cisplatin plus mitotane (PDP-M)) in preclinical in vitro and in vivo models. In addition, based on an extraordinary uptake phenomenon of liposomes in ACC cells, we further evaluated liposomal variants of these protocols (etoposide, liposomal doxorubicin, liposomal cisplatin plus mitotane (LEDP-M) and nab-paclitaxel, liposomal doxorubicin, liposomal cisplatin plus mitotane (LPDP-M)). In vitro, PDP-M was more potent in the induction of apoptosis and inhibition of cell viability as well as cell proliferation than EDP-M. Following the administration of a single therapeutic cycle, we further demonstrated that LEDP-M and LPDP-M exerted significant antitumoral effects in vivo, which were not as evident upon EDP-M and PDP-M treatments. These results were confirmed in a long-term experiment, in which the highest and sustained antitumoral effects were observed for LEDP-M. In summary, liposomal cytostatic substances could represent a promising option that deserves testing in appropriate clinical protocols for the treatment of ACC patients.