Hypoxia sustains glioblastoma radioresistance through ERKs/DNA-PKcs/HIF-1α functional interplay.

The molecular mechanisms by which glioblastoma multiforme (GBM) refracts and becomes resistant to radiotherapy treatment remains largely unknown. This radioresistance is partly due to the presence of hypoxic regions, which are frequently found in GBM tumors. We investigated the radiosensitizing effects of MEK/ERK inhibition on GBM cell lines under hypoxic conditions. Four human GBM cell lines, T98G, U87MG, U138MG and U251MG were treated with the MEK/ERK inhibitor U0126, the HIF-1α inhibitor FM19G11 or γ-irradiation either alone or in combination under hypoxic conditions. Immunoblot analysis of specific proteins was performed in order to define their anti­oncogenic or radiosensitizing roles in the different experimental conditions. MEK/ERK inhibition by U0126 reverted the transformed phenotype and significantly enhanced the radiosensitivity of T98G, U87MG, U138MG cells but not of the U251MG cell line under hypoxic conditions. U0126 and ERK silencing by siRNA reduced the levels of DNA protein kinase catalytic subunit (DNA-PKcs), Ku70 and K80 proteins and clearly reduced HIF-1α activity and protein expression. Furthermore, DNA-PKcs siRNA-mediated silencing counteracted HIF-1α activity and downregulated protein expression suggesting that ERKs, DNA-PKcs and HIF-1α cooperate in radioprotection of GBM cells. Of note, HIF-1α inhibition under hypoxic conditions drastically radiosensitized all cell lines used. MEK/ERK signal transduction pathway, through the sustained expression of DNA-PKcs, positively regulates HIF-1α protein expression and activity, preserving GBM radioresistance in hypoxic condition.

Identification of novel genetic variants in phosphodiesterase 8B (PDE8B), a cAMP-specific phosphodiesterase highly expressed in the adrenal cortex, in a cohort of patients with adrenal tumours.

BACKGROUND: Genetic aberrations in various components of cAMP signalling pathway predispose to endocrine tumours. Mutations in the phosphodiesterases (PDEs) are involved in the predisposition to adrenocortical neoplastic conditions. OBJECTIVE: To screen for genetic variations in PDE8B among patients with different types of adrenocortical tumours. DESIGN AND SUBJECTS: This is a case-control study followed by functional analyses. Two hundred and sixteen unrelated patients with different types of adrenocortical tumours and 192 healthy control individuals participated in the study. METHODS: Bidirectional Sanger sequencing, in vitro cell line transfection and in silico modelling are used in this study. RESULTS: Nine different PDE8B sequence changes, six novel and three previously reported, were identified in our patients and controls. Two of the variations, seen only in the patient group, showed significant potential to impair protein function, both in vitro and in silico. CONCLUSION: PDE8B is another PDE gene in which variations may contribute to predisposition of adrenocortical tumours.

A rare cause of hypertestosteronemia in a 68-year-old patient: a Leydig cell tumor due to a somatic GNAS (guanine nucleotide-binding protein, alpha-stimulating activity polypeptide 1)-activating mutation.

Leydig cell tumors of the testis are the most common type of non-germ cell testicular tumors. In adult patients, gynecomastia, oligozoospermia, erectile dysfunction, and other signs of feminization can be present, whereas testosterone levels are frequently in the normal range or slightly reduced. We describe a patient with a history of impaired sexual function, as well as progressive enlargement of the left testis, without gynecomastia. Hormonal evaluation demonstrated very high testosterone, estrogen, and pan-alpha-inhibin levels. Magnetic resonance imaging revealed the presence of left testicular hypertrophy without evidence of testicular mass. After left orchiectomy, histologic examination confirmed the diagnosis of Leydig cell tumor, and steroid hormone levels normalized. A heterozygous missense somatic gsp mutation (R201C) was found in tumoral tissue, whereas no mutation was found in the surrounding normal tissue or in leukocyte DNA. This case provides evidence that somatic activating gsp mutation in Leydig cells may result in tumor development, leading to overexpression of the inhibin alpha subunit and hyperactivity of the testosterone biosynthetic pathway.

Frequent phosphodiesterase 11A gene (PDE11A) defects in patients with Carney complex (CNC) caused by PRKAR1A mutations: PDE11A may contribute to adrenal and testicular tumors in CNC as a modifier of the phenotype.

BACKGROUND: Carney complex (CNC) is an autosomal dominant multiple neoplasia, caused mostly by inactivating mutations of the regulatory subunit 1A of the protein kinase A (PRKAR1A). Primary pigmented nodular adrenocortical disease (PPNAD) is the most frequent endocrine manifestation of CNC with a great inter-individual variability. Germline, protein-truncating mutations of phosphodiesterase type 11A (PDE11A) have been described to predispose to a variety of endocrine tumors, including adrenal and testicular tumors. OBJECTIVES: Our objective was to investigate the role of PDE11A as a possible gene modifier of the phenotype in a series of 150 patients with CNC. RESULTS: A higher frequency of PDE11A variants in patients with CNC compared with healthy controls was found (25.3 vs. 6.8%, P < 0.0001). Among CNC patients, those with PPNAD were significantly more frequently carriers of PDE11A variants compared with patients without PPNAD (30.8 vs. 13%, P = 0.025). Furthermore, men with PPNAD were significantly more frequently carriers of PDE11A sequence variants (40.7%) than women with PPNAD (27.3%) (P < 0.001). A higher frequency of PDE11A sequence variants was also found in patients with large-cell calcifying Sertoli cell tumors (LCCSCT) compared with those without LCCSCT (50 vs. 10%, P = 0.0056). PDE11A variants were significantly associated with the copresence of PPNAD and LCCSCT in men: 81 vs. 20%, P < 0.004). The simultaneous inactivation of PRKAR1A and PDE11A by small inhibitory RNA led to an increase in cAMP-regulatory element-mediated transcriptional activity under basal conditions and after stimulation by forskolin. CONCLUSIONS: We demonstrate, in a large cohort of CNC patients, a high frequency of PDE11A variants, suggesting that PDE11A is a genetic modifying factor for the development of testicular and adrenal tumors in patients with germline PRKAR1A mutation.

Transcriptome analysis reveals that p53 and {beta}-catenin alterations occur in a group of aggressive adrenocortical cancers.

Adrenocortical carcinoma (ACC) is a rare disease with an overall poor but heterogeneous prognosis. This heterogeneity could reflect different mechanisms of tumor development. Gene expression profiling by transcriptome analysis led to ACC being divided into two groups of tumors with very different outcomes. Somatic inactivating mutations of the tumor suppressor gene TP53 and activating mutations of the proto-oncogene ß-catenin (CTNNB1) are the most frequent mutations identified in ACC. This study investigates the correlation between p53 and ß-catenin alterations and the molecular classification of ACC by transcriptome analysis of 51 adult sporadic ACCs. All TP53 and CTNNB1 mutations seemed to be mutually exclusive and were observed only in the poor-outcome ACC group. Most of the abnormal p53 and ß-catenin immunostaining was also found in this group. Fifty-two percent of the poor-outcome ACC group had TP53 or CTNNB1 mutations and 60% had abnormal p53 or ß-catenin immunostaining. Unsupervised clustering transcriptome analysis of this poor-outcome group revealed three different subgroups, two of them being associated with p53 or ß-catenin alterations, respectively. Analysis of p53 and ß-catenin target gene expressions in each cluster confirmed a profound and anticipated effect on tumor biology, with distinct profiles logically associated with the respective pathway alterations. The third group had no p53 or ß-catenin alteration, suggesting other unidentified molecular defects. This study shows the important respective roles of p53 and ß-catenin in ACC development, delineating subgroups of ACC with different tumorigenesis and outcomes.

Phosphodiesterase 11A (PDE11A) and genetic predisposition to adrenocortical tumors.

PURPOSE: We have reported previously nonsense inactivating mutations of the phosphodiesterase 11A (PDE11A) gene in patients with micronodular adrenocortical hyperplasia and Cushing syndrome. The aim of this study is to investigate the presence of somatic or germ-line PDE11A mutations in various types of adrenocortical tumors: ACTH-independent macronodular adrenocortical hyperplasia (AIMAH), adrenocortical adenoma (ACA), and adrenocortical cancer (ACC). EXPERIMENTAL DESIGN: PDE11A was sequenced in 117 adrenocortical tumors and 192 controls subjects; immunohistochemistry for PDE11A and tumor cyclic AMP levels were studied in a subgroup of adrenocortical tumors. RESULTS: One PDE11A inactivating mutation (R307X) was found in one ACA, 22 germ-line missense variants (18.8%) were found in adrenocortical tumors, and only 11 missense variants (5.7%) were found in controls. By comparing the common mutations, a higher frequency of mutations in adrenocortical tumors than in age/sex-matched controls were observed [16% versus 10% in ACC, 19% versus 10% in ACA, and 24% versus 9% in AIMAH; odds ratio (OR), 3.53; P = 0.05]. Somatic DNA from adrenocortical tumors with missense variants showed a wild-type allelic loss. A significant difference between ACC and controls was observed for a polymorphism in exon 6 (E421E; OR, 2.1; P = 0.03) and three associated polymorphisms located in intron 10-exon 11-intron 11 (OR, 0.5; P = 0.01). In AIMAH/ACA, cyclic AMP levels were higher than in normal adrenals and decreased PDE11A immunostaining was present in adrenocortical tumors with PDE11A variants. CONCLUSIONS: The present investigation of a large cohort of adrenocortical tumors suggests that PDE11A sequence defects predispose to a variety of lesions (beyond micronodular adrenocortical hyperplasia) and may contribute to the development of these tumors in the general population.

Adrenocortical cancer: pathophysiology and clinical management.

Adrenocortical cancer (ACC) is a rare tumor with a poor prognosis. By contrast, benign adrenocortical tumors are frequent, underlying the importance of a correct diagnosis of malignancy of such tumors. ACC can be diagnosed by the investigation of endocrine signs of steroid excess, symptoms due to tumor growth or an adrenal incidentaloma. Hormonal investigations demonstrate in most ACC steroid oversecretion, the dominant characteristics being a co-secretion of cortisol and androgens. Imaging by CT-scan or MRI shows a large heterogeneous tumor with a low fat content. Careful pathological investigation with the assessment of the Weiss score is important for the diagnosis of malignancy. Molecular markers can also be helpful and in the future might be important for prognosis. Tumors localized to the adrenal gland (McFarlane stages 1 and 2) have a better outcome than invasive and metastatic tumors (stages 3 and 4). Tumor removal by a specialized team is crucial for treatment and should always aim at complete removal. In patients with metastatic or progressive disease, medical treatment is started with mitotane that requires a close monitoring of its blood level. Surgery is indicated when possible for local recurrence but also in some cases of metastasis. Local treatment (radiofrequency, chemoembolization, and radiation therapy) can have some indications for metastatic disease. In patients with disease progression cytotoxic chemotherapy can be used. Despite the best care, the overall prognosis of ACC is poor with a 5-year survival rate below 30% in most series. Therefore, progress in the understanding of the pathophysiology of ACC is important. Despite the rarity of ACC, significant advances have been made in the understanding of its pathogenesis the last decade. These progresses came mainly from the study of the genetics of ACC, both at the germline level in rare familial diseases, and at the somatic level by the study of molecular alterations in sporadic tumors. These advances underline the importance of genetic alterations in ACC development and point-out to various chromosomal regions (2, 11p15, 11q, 17p13) and genes (IGF-II, p53, beta-catenin, ACTH receptor). This review will summarize these advances as well as the current clinical management of ACC.

Somatic TP53 mutations are relatively rare among adrenocortical cancers with the frequent 17p13 loss of heterozygosity.

PURPOSE: Allelic losses [loss of heterozygosity (LOH)] at the 17p13 locus are frequent (85%) in adrenocortical cancers. The tumor suppressor gene TP53 is located at 17p13. The aim of the study was to determine the frequency of TP53 somatic inactivating mutations in adrenocortical tumors with 17p13 LOH and their clinico-biological correlations. EXPERIMENTAL DESIGN: TP53 somatic mutations, intragenic LOH (VNTR1 marker), and p53 overexpression were studied in 36 adrenocortical tumors with 17p13 LOH determined by Southern blot. RESULTS: TP53 mutations were detected in 33% of the tumors, and VNTR1 LOH was present in 44% of the cases and did not always correlate with the presence of a TP53 mutation. Only the TP53-mutant tumors exhibit a strong nuclear immunoreactivity. TP53-mutant tumors were significantly larger than wild-type TP53 tumors (median tumor weight: 640 versus 185 g; P=0.02), were associated with a more advanced stage of tumor progression (MacFarlane stage IV; P=0.01), and had a shorter disease-free survival (P=0.03). CONCLUSIONS: The finding that only a minority of adrenocortical tumors with 17p13 LOH had either a VNTR1 LOH or a TP53 mutation indicates that TP53 might not be the only or major tumor suppressor gene at 17p13 involved in adrenocortical cancer progression. We suggest that a genetic instability of the 17p13 region, occurring early in adrenocortical cancer development, involves various genes located in this region. TP53 might be only one of them, and its alteration by the occurrence of inactivating mutation is associated with the development of more aggressive tumors.

A genome-wide scan identifies mutations in the gene encoding phosphodiesterase 11A4 (PDE11A) in individuals with adrenocortical hyperplasia.

Phosphodiesterases (PDEs) regulate cyclic nucleotide levels. Increased cyclic AMP (cAMP) signaling has been associated with PRKAR1A or GNAS mutations and leads to adrenocortical tumors and Cushing syndrome. We investigated the genetic source of Cushing syndrome in individuals with adrenocortical hyperplasia that was not caused by known defects. We performed genome-wide SNP genotyping, including the adrenocortical tumor DNA. The region with the highest probability to harbor a susceptibility gene by loss of heterozygosity (LOH) and other analyses was 2q31-2q35. We identified mutations disrupting the expression of the PDE11A isoform-4 gene (PDE11A) in three kindreds. Tumor tissues showed 2q31-2q35 LOH, decreased protein expression and high cyclic nucleotide levels and cAMP-responsive element binding protein (CREB) phosphorylation. PDE11A codes for a dual-specificity PDE that is expressed in adrenal cortex and is partially inhibited by tadalafil and other PDE inhibitors; its germline inactivation is associated with adrenocortical hyperplasia, suggesting another means by which dysregulation of cAMP signaling causes endocrine tumors.

Smad3 knock-out mice as a useful model to study intestinal fibrogenesis.

AIM: To evaluate the possible differences in morphology and immunohistochemical expression of CD3, transforming growth factor beta1 (TGF-beta1), Smad7, alpha-smooth muscle actin (alpha-Sma), and collagen types I-VII of small and large intestine in Smad3 null and wild-type mice. METHODS: Ten null and ten wild-type adult mice were sacrificed at 4 mo of age and the organs (esophagus, small and large bowel, ureters) were collected for histology (hematoxylin and eosin, Masson thrichrome, silver staining), morphometry and immunohistochemistry analysis. TGF-beta1 levels of intestinal tissue homogenates were assessed by ELISA. RESULTS: No macroscopic intestinal lesions were detected both in null and wild-type mice. Histological and morphometric evaluation revealed a significant reduction in muscle layer thickness of small and large intestine in null mice as compared to wild-type mice. Immunohistochemistry evaluation showed a significant increase of CD3+ T cell, TGF-beta1 and Smad7 staining in the small and large intestine mucosa of Smad3 null mice as compared to wild-type mice. Alpha-Sma and collagen I-VII staining of small and large intestine did not differ between the two groups of mice. TGF-beta1 levels of colonic tissue homogenates were significantly higher in null mice than in wild-type mice. In preliminary experiments a significant reduction of TNBS-induced intestinal fibrosis was observed in null mice as compared to wild-type mice. CONCLUSION: Smad3 null mice are a useful model to investigate the in vivo role of the TGF-beta/Smad signalling pathway in intestinal inflammation and fibrosis.

Diagnosis and management of pituitary tumours in the elderly: a review based on personal experience and evidence of literature.

An increasing proportion of pituitary adenomas are recognized in the elderly, raising the question of their optimal diagnosis and management. Age-related endocrine changes and associated diseases may significantly modify the clinical presentation and hormonal evaluation of these patients. About 80% of pituitary adenomas in this age group are non-secreting, requiring careful differential diagnosis with non-adenomatous sellar lesions. In this group, visual deterioration and hypopituitarism remain the leading symptoms. Recognized secreting tumours are mainly GH-secreting, most of them intrasellar, followed by prolactinomas, which present as clinically non-secreting and are usually invasive. Cushing's disease appears as a very rare eventuality in the elderly. Optimal therapeutic management should aim to control the disease while preserving or improving patient's quality of life. Transsphenoidal surgery has proved to be an efficient and well-tolerated option for non-secreting adenomas with visual defects and intrasellar GH-secreting adenomas, being able to improve metabolic and cardiovascular complications of acromegaly even in this age group. In contrast, dopamine-agonist drugs can be proposed as a primary therapy for prolactinomas even in the presence of severe neurological complications. Because the use of radiotherapy is hampered by its delay of action and potential neurological side effects, its indications should be better defined in this age group. The clinical importance of hypopituitarism should not be underestimated, and thyroid- and adrenal-replacement therapy are mandatory in the presence of documented hormone deficiency, carefully avoiding overtreatment in order to limit possible side effects on the cardiovascular system and bone mineralization. Indications for GH- and sex steroid-replacement therapy still await age-specific guidelines.