Marine Guillaud-Bataille

Mutations and Polymorphisms in the Gene Encoding Regulatory Subunit Type 1-alpha of Protein Kinase A (PRKAR1A): An Update

PRKAR1A encodes the regulatory subunit type 1‐alpha (RIα) of the cyclic adenosine monophosphate (cAMP)‐dependent protein kinase (PKA). Inactivating PRKAR1A mutations are known to be responsible for the multiple neoplasia and lentiginosis syndrome Carney complex (CNC). To date, at least 117 pathogenic variants in PRKAR1A have been identified (online database: http://prkar1a.nichd.nih.gov). The majority are subject to nonsense mediated mRNA decay (NMD), leading to RIα haploinsufficiency and, as a result, activated cAMP signaling. Recently, it became apparent that CNC may be caused not only by RIα haploinsufficiency, but also by the expression of altered RIα protein, as proven by analysis of expressed mutations in the gene, consisting of aminoacid substitutions and in‐frame genetic alterations. In addition, a new subgroup of mutations that potentially escape NMD and result in CNC through altered (rather than missing) protein has been analyzed—these are frame‐shifts in the 3′ end of the coding sequence that shift the stop codon downstream of the normal one. The mutation detection rate in CNC patients is recently estimated at above 60%; PRKAR1A mutation‐negative CNC patients are characterized by significant phenotypic heterogeneity. In this report, we present a comprehensive analysis of all presently known PRKAR1A sequence variations and discuss their molecular context and clinical phenotype. Hum Mutat 31:369–379, 2010. Published 2010 Wiley‐Liss, Inc.

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.

Mutations of the Gene for the Aryl Hydrocarbon Receptor-Interacting Protein in Pituitary Adenomas

Heterozygous germline mutations in the gene encoding the aryl hydrocarbon receptor-interacting protein (AIP) were first described in two Finnish families with pituitary adenomas. The gene is involved in about 15% of familial isolated pituitary adenomas (FIPA), in about 50% of cases of familial acromegaly and in a small proportion of acromegalic patients with sporadic presentation. This review describes the genetic and clinical features of published patients with AIP, with either familial or sporadic pituitary tumors. A genotype-phenotype correlation is proposed: patients with AIP mutations resulting in a truncated protein are significantly younger than those bearing a mutation which preserves the structure of the C-terminal end of the protein (22.7 ± 9.6 vs. 29.8 ± 10.9 years). Pituitary tumors linked to AIP mutations are almost exclusively somatotropic (87.5%, n = 56/64) or lactotropic (9.4%, n = 6). Patients with AIP mutations are mostly men (70%, 44 M/19 F), suffer macroadenomas (97%) and are younger at diagnosis (24.4 ± 10.5 years) than unselected patients with pituitary tumors. Thus, AIP is involved in the development of pituitary tumors, especially involving the somatomammotroph lineage. Genetic testing could be discussed for FIPAs and in young acromegalic patients with a sporadic presentation. Functional studies are needed to understand AIP-induced tumorigenesis.

TMEM127 Screening in a Large Cohort of Patients with Pheochromocytoma and/or Paraganglioma

CONTEXT TMEM127 is a novel pheochromocytoma (PCC) susceptibility gene. OBJECTIVES Our aim was to clearly determine the indications for TMEM127 genetic testing in patients with PCC and/or paraganglioma (PGL). PATIENTS AND METHODS Germline DNA from 642 unrelated patients who did not carry mutations in major PCC susceptibility genes was analyzed. Five hundred fifty-nine patients were affected by PCC, 72 by PGL (22 with head and neck and 50 with thoracic or abdominal location), and 11 by both PCC and PGL. Analysis of the TMEM127 gene was performed by direct sequencing and quantitative multiplex PCR of short fluorescent fragments. RESULTS In our cohort six mutations (0.9%) were identified. Three of them (p.Ala47Asp, p.Gln64HisfsX18, p.Tyr164X) were found in patients exhibiting clinical criteria for a hereditary disease (young age at diagnosis, bilateral PCC, or family history). The three others (p.Gln157X, p.Val68SerfsX13, p.Val90Met) were detected in patients with an apparently sporadic presentation. No mutation was found among patients with PGL, and no large chromosomal rearrangement spanning the TMEM127 gene was detected. CONCLUSIONS Our results combined with the two previous studies suggest that direct sequencing of TMEM127 should be considered, after a negative screening of VHL, RET, SDHB, and SDHD genes, in patients with PCC.

Clinical and Pathophysiological Implications of Chromosomal Alterations in Adrenocortical Tumors: An Integrated Genomic Approach

PURPOSE Diagnosing malignancy of adrenocortical tumors (ACT) and predicting prognosis in carcinomas are often challenging. Transcriptome markers have recently emerged, providing promising clinical relevance and improved pathophysiological knowledge. Whether tumoral chromosomal alterations provide similar information is not known. The aim was to evaluate the diagnostic and prognostic value of chromosomal alterations in ACT and to identify genes associated with benign and malignant tumorigenesis. EXPERIMENTAL DESIGN Chromosomal alterations of 86 adenomas and 52 carcinomas were identified by comparative genomic hybridization arrays and/or quantitative PCR. RESULTS A larger proportion of the genome is altered in carcinomas compared with adenomas (44 vs. 10%, P = 2.10(-10)). In adenomas, the 9q34 region, which includes the steroidogenic factor 1 locus, is commonly gained and associated with an overexpression of steroidogenic factor 1 (SF-1). In carcinomas, recurrent gains include chromosomes 5, 7, 12, 16, 19, and 20 and recurrent losses chromosomes 13 and 22. Filtering the genes from these regions according to their expression profile identified genes potentially relevant to adrenocortical tumorigenesis. A diagnostic tool was built by combining DNA copy number estimates at six loci (5q, 7p, 11p, 13q, 16q, and 22q). This tool discriminates carcinomas from adenomas in an independent validation cohort (sensitivity 100%, specificity 83%). In carcinomas, the number of chromosomal alterations was not associated with survival (Cox P = 0.84). A prognostic tool based on tumor DNA was designed with a clustering strategy and validated in an independent cohort. CONCLUSIONS Chromosomal alterations in ACT discriminate carcinomas from adenomas and contain prognostic information. Chromosomal alterations alter the expression of genes important for tumorigenesis.

The pathophysiology, diagnosis and prognosis of adrenocortical tumors revisited by transcriptome analyses

Analyzing gene expression (transcriptome) in tissue is now reliable using industrial pangenomic microarrays. Accumulating data on adrenal cortex and adrenocortical tumor transcriptomes have already identified striking transcriptome differences not only between adenoma and carcinoma but also between two sets of carcinoma, which have very different prognoses. These findings result in the development of diagnostic and prognostic molecular predictors, which improve the outcome determination compared with standard clinical and pathological tools. These transcriptome data observing adrenocortical tumor phenotype in great but complex detail, combined with genomic and proteomic information, will function for future research investigating the pathophysiology of their tumorigenesis and hormonal secretion.

Silencing mutated β-catenin inhibits cell proliferation and stimulates apoptosis in the adrenocortical cancer cell line H295R

Context Adrenocortical carcinoma (ACC) is a rare and highly aggressive endocrine neoplasm, with limited therapeutic options. Activating β-catenin somatic mutations are found in ACC and have been associated with a poor clinical outcome. In fact, activation of the Wnt/β-catenin signaling pathway seems to play a major role in ACC aggressiveness, and might, thus, represent a promising therapeutic target. Objective Similar to patient tumor specimen the H295 cell line derived from an ACC harbors a natural activating β-catenin mutation. We herein assess the in vitro and in vivo effect of β-catenin inactivation using a doxycyclin (dox) inducible shRNA plasmid in H295R adrenocortical cancer cells line (clone named shβ). Results Following dox treatment a profound reduction in β-catenin expression was detectable in shβ clones in comparison to control clones (Ctr). Accordingly, we observed a decrease in Wnt/βcatenin-dependent luciferase reporter activity as well as a decreased expression of AXIN2 representing an endogenous β-catenin target gene. Concomitantly, β-catenin silencing resulted in a decreased cell proliferation, cell cycle alterations with cell accumulation in the G1 phase and increased apoptosis in vitro. In vivo, on established tumor xenografts in athymic nude mice, 9 days of β-catenin silencing resulted in a significant reduction of CTNNB1 and AXIN2 expression. Moreover, continous β-catenin silencing, starting 3 days after tumor cell inoculation, was associated with a complete absence of tumor growth in the shβ group while tumors were present in all animals of the control group. Conclusion In summary, these experiments provide evidences that Wnt/β-catenin pathway inhibition in ACC is a promising therapeutic target.

IGF2 Promotes Growth of Adrenocortical Carcinoma Cells, but Its Overexpression Does Not Modify Phenotypic and Molecular Features of Adrenocortical Carcinoma

Insulin-like growth factor 2 (IGF2) overexpression is an important molecular marker of adrenocortical carcinoma (ACC), which is a rare but devastating endocrine cancer. It is not clear whether IGF2 overexpression modifies the biology and growth of this cancer, thus more studies are required before IGF2 can be considered as a major therapeutic target. We compared the phenotypical, clinical, biological, and molecular characteristics of ACC with or without the overexpression of IGF2, to address these issues. We also carried out a similar analysis in an ACC cell line (H295R) in which IGF2 expression was knocked down with si- or shRNA. We found no significant differences in the clinical, biological and molecular (transcriptomic) traits between IGF2-high and IGF2-low ACC. The absence of IGF2 overexpression had little influence on the activation of tyrosine kinase pathways both in tumors and in H295 cells that express low levels of IGF2. In IGF2-low tumors, other growth factors (FGF9, PDGFA) are more expressed than in IGF2-high tumors, suggesting that they play a compensatory role in tumor progression. In addition, IGF2 knock-down in H295R cells substantially impaired growth (>50% inhibition), blocked cells in G1 phase, and promoted apoptosis (>2-fold). Finally, analysis of the 11p15 locus showed a paternal uniparental disomy in both IGF2-high and IGF2-low tumors, but low IGF2 expression could be explained in most IGF2-low ACC by an additional epigenetic modification at the 11p15 locus. Altogether, these observations confirm the active role of IGF2 in adrenocortical tumor growth, but also suggest that other growth promoting pathways may be involved in a subset of ACC with low IGF2 expression, which creates opportunities for the use of other targeted therapies.

p.Ala541Thr variant of MEN1 gene: A non deleterious polymorphism or a pathogenic mutation?

CONTEXT Multiple Endocrine Neoplasia Type 1 (MEN1) is an autosomal dominant inherited syndrome, related to mutations in the MEN1 gene. Controversial data suggest that the nonsynonymous p.Ala541Thr variant, usually considered as a non-pathogenic polymorphism, may be associated with an increased risk of MEN1-related lesions in carriers. OBJECTIVE The aim of this study was to evaluate the pathogenic influence of the p.Ala541Thr variant on clinical and functional outcomes. PATIENTS AND METHODS We analysed a series of 55 index patients carrying the p.Ala541Thr variant. Their clinical profile was compared to that of 117 MEN1 patients. The biological impact of the p.Ala541Thr variant on cell growth was additionally investigated on menin-deficient Leydig cell tumour (LCT)10 cells generated from Men1+/Men1- heterozygous knock-out mice, and compared with wild type (WT). RESULTS The mean age at first appearance of endocrine lesions was similar in both p.Ala541Thr carriers and MEN1 patients, but no p.Ala541Thr patient had more than one cardinal MEN1 lesion at initial diagnosis. A second MEN1 lesion was diagnosed in 13% of MEN1 patients and in 7% of p.Ala541Thr carriers in the year following preliminary diagnosis. Functional studies on LCT10 cells showed that overexpression of the p.Ala541Thr variant did not inhibit cell growth, which is in direct contrast to results obtained from investigation of WT menin protein. CONCLUSION Taken together, these data raise the question of a potential pathogenicity of the p.Ala541Thr missense variant of menin that commonly occurs within the general population. Additional studies are required to investigate whether it may be involved in a low-penetrance MEN1 phenotype.