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.
Masanori Murakami, Takanobu Yoshimoto, Kazuhiko Nakabayashi, Yujiro Nakano, Takahiro Fukaishi, Kyoichiro Tsuchiya, Isao Minami, Ryotaro Bouchi, Kohji Okamura, Yasuhisa Fujii, Koshi Hashimoto, Ken-ichiro Hata, Kazunori Kihara, and Yoshihiro Ogawa
The pathophysiology of aldosterone-producing adenomas (APAs) has been investigated via genetic approaches and the pathogenic significance of a series of somatic mutations, including KCNJ5, has been uncovered. However, how the mutational status of an APA is associated with its molecular characteristics, including its transcriptome and methylome, has not been fully understood. This study was undertaken to explore the molecular characteristics of APAs, specifically focusing on APAs with KCNJ5 mutations as opposed to those without KCNJ5 mutations, by comparing their transcriptome and methylome status. Cortisol-producing adenomas (CPAs) were used as reference. We conducted transcriptome and methylome analyses of 29 APAs with KCNJ5 mutations, 8 APAs without KCNJ5 mutations and 5 CPAs. Genome-wide gene expression and CpG methylation profiles were obtained from RNA and DNA samples extracted from these 42 adrenal tumors. Cluster analysis of the transcriptome and methylome revealed molecular heterogeneity in APAs depending on their mutational status. DNA hypomethylation and gene expression changes in Wnt signaling and inflammatory response pathways were characteristic of APAs with KCNJ5 mutations. Comparisons between transcriptome data from our APAs and that from normal adrenal cortex obtained from the Gene Expression Omnibus suggested similarities between APAs with KCNJ5 mutations and zona glomerulosa. The present study, which is based on transcriptome and methylome analyses, indicates the molecular heterogeneity of APAs depends on their mutational status. Here, we report the unique characteristics of APAs with KCNJ5 mutations.
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.
Fabio L Forti and Hugo A Armelin
Arginine vasopressin (AVP), a vasoactive peptide hormone that binds to three G-protein coupled receptors (V1R, V2R, and V3R), has long been known to activate V1R and elicit mitogenesis in several cell types, including adrenal glomerulosa cells. However, in the mouse Y1 adrenocortical malignant cell line, AVP triggers not only a canonical mitogenic response but also novel RhoA-GTP-dependent mechanisms which downregulate cyclin D1, irreversibly inhibiting K-ras oncogene-driven proliferation. In Y1 cells, AVP blocks cyclin D1 expression, induces senescence-associated β-galactosidase (SAβ-Gal) and inhibits proliferation. However, ectopic expression of cyclin D1 renders Y1 cells resistant to both SAβ-Gal induction and proliferation inhibition by AVP. In addition, ectopic expression of the dominant negative RhoAN19 mutant blocks RhoA activation, yielding Y1 cell sub-lines which are no longer susceptible to cyclin D1 downregulation, SAβ-Gal induction, or proliferation inhibition by AVP. Furthermore, inhibiting RhoA with C3 exoenzyme protects Y1 cells from AVP proliferation inhibition and SAβ-Gal induction. On the other hand, AVP treatment does not activate caspases 3 and 7, and the caspase inhibitor Ac-DEVD-CMK does not protect Y1 cells from proliferation inhibition by AVP, implying that AVP does not trigger apoptosis. These results underline a pivotal survival activity of cyclin D1 that protects K-ras oncogene-dependent malignant cells from senescence.
Pasqualino Malandrino, Abir Al Ghuzlan, Marine Castaing, Jacques Young, Bernard Caillou, Jean-Paul Travagli, Dominique Elias, Thierry de Baere, Clarisse Dromain, Angelo Paci, Philippe Chanson, Martin Schlumberger, Sophie Leboulleux, and Eric Baudin
To progress in the stratification of the first-line therapeutic management of metastatic adrenocortical carcinoma (ACC), we searched for prognostic parameters of survival in patients treated with combined mitotane- and cisplatinum-based chemotherapy as first-line. We retrospectively studied prospectively collected parameters from 131 consecutive patients with metastatic ACC (44 with a tissue specimen available) treated at the Gustave Roussy Institute with mitotane- and platinum-based chemotherapy. Fifty-five patients with clinical, pathological, and morphological data available together with treatment characteristics including detailed follow-up were enrolled. Plasma mitotane levels and ERCC1 protein staining were analyzed. Response was analyzed according to RECIST criteria as well as overall survival (OS) from the start of cisplatinum-based chemotherapy. Parameters impacting on OS were evaluated by univariate analysis, and then analyzed by multivariate analysis. Using a landmark method, OS according to response to chemotherapy was analyzed. Objective response to combined mitotane- and cisplatinum-based chemotherapy was 27.3%. Median OS was 1 year. In the univariate analysis, resection of the primary, time since diagnosis, mitotane monotherapy as single first-line treatment, number of affected organs, plasma mitotane above 14 mg/l, and objective response were predictors of survival. In the multivariate analysis, mitotane level ≥14 mg/l and objective response to platinum-based chemotherapy were found to be independent predictors of survival (P=0.03 and <0.001). Our study suggests a prognostic role for mitotane therapy and objective response to platinum-based chemotherapy.
S G Creemers, P M van Koetsveld, F J van Kemenade, T G Papathomas, G J H Franssen, F Dogan, E M W Eekhoff, P van der Valk, W W de Herder, J A M J L Janssen, R A Feelders, and L J Hofland
Adrenocortical carcinoma (ACC) is a rare malignancy with a poor prognosis. Discrimination of ACCs from adrenocortical adenomas (ACAs) is challenging on both imaging and histopathological grounds. High IGF2 expression is associated with malignancy, but shows large variability. In this study, we investigate whether specific methylation patterns of IGF2 regulatory regions could serve as a valuable biomarker in distinguishing ACCs from ACAs. Pyrosequencing was used to analyse methylation percentages in DMR0, DMR2, imprinting control region (ICR) (consisting of CTCF3 and CTCF6) and the H19 promoter. Expression of IGF2 and H19 mRNA was assessed by real-time quantitative PCR. Analyses were performed in 24 ACCs, 14 ACAs and 11 normal adrenals. Using receiver operating characteristic (ROC) analysis, we evaluated which regions showed the best predictive value for diagnosis of ACC and determined the diagnostic accuracy of these regions. In ACCs, the DMR0, CTCF3, CTCF6 and the H19 promoter were positively correlated with IGF2 mRNA expression (P<0.05). Methylation in the most discriminating regions distinguished ACCs from ACAs with a sensitivity of 96%, specificity of 100% and an area under the curve (AUC) of 0.997±0.005. Our findings were validated in an independent cohort of 9 ACCs and 13 ACAs, resulting in a sensitivity of 89% and a specificity of 92%. Thus, methylation patterns of IGF2 regulatory regions can discriminate ACCs from ACAs with high diagnostic accuracy. This proposed test may become the first objective diagnostic tool to assess malignancy in adrenal tumours and facilitate the choice of therapeutic strategies in this group of patients.
Susanna Vuorenoja, Adolfo Rivero-Müller, Adam J Ziecik, Ilpo Huhtaniemi, Jorma Toppari, and Nafis A Rahman
Novel strategies are needed for the treatment of adrenocortical tumors that are usually resistant to chemotherapy. Hecate, a 23-amino acid lytic peptide, was conjugated to the 15-amino acid (81–95) fragment of the human chorionic gonadotropin β (CGβ) chain, which would selectively kill cancer cells expressing the LH receptor (LHR) sparing the normal ones with LHR. To prove the principle that Hecate-CGβ conjugate may eradicate tumors ectopically expressing plasma membrane receptors, transgenic (TG) inhibin α-subunit promoter (inhα)/Simian Virus 40 T-antigen mice, expressing LHR in their adrenal gland tumors, were used as the experimental model. Wild-type control littermates and TG mice with adrenal tumors were treated with either Hecate or Hecate-CGβ conjugate at the age of 6.5 months for 3 weeks and killed 7 days after the last treatment. The Hecate-CGβ conjugate reduced the adrenal tumor burden significantly in TG male but not in female mice, in comparison with Hecate-treated mice. Hecate-CGβ conjugate treatment did not affect normal adrenocortical function as the serum corticosterone level between Hecate and Hecate-CGβ conjugate groups were similar. The mRNA and protein expressions of GATA-4 and LHR colocalized only in tumor area, and a significant downregulation of gene expression was found after the Hecate-CGβ conjugate in comparison with Hecate- and/or non-treated adrenal tumors by western blotting. This finding provides evidence for a selective destruction of the tumor cells by the Hecate-CGβ conjugate. Hereby, our findings support the principle that Hecate-CGβ conjugate is able to specifically destroy tumor cells that ectopically express LHR.