Identification of genetic alterations of AXIN2 gene in adrenocortical tumors.

BACKGROUND: Mutations of the ß-catenin gene (CTNNB1), which lead to constitutive activation of Wnt signaling, have recently been described in adrenocortical adenomas (AA) and carcinomas (ACC). However, somatic CTNNB1 mutations may explain only about 50% of ß-catenin accumulation observed in adrenocortical tumors, indicating that other components of the Wnt pathway may be involved. OBJECTIVE: The objective of the study was to investigate whether alterations in AXIN2 may be present in adrenocortical tumors. METHODS: We studied 49 human adrenocortical samples: 30 AA, six ACC, five primary pigmented nodular adrenocortical disease five ACTH-independent macronodular adrenal hyperplasias (AIMAH), and three ACTH-dependent hyperplasias in addition to the human ACC cell lines SW13 and H295R. Samples were screened for somatic genetic alterations in exon 3 of CTNNB1 and exons 5, 7, and 9 of AXIN2. RESULTS: We found an in-frame, 12-bp deletion beginning at coding nucleotide 2013 in exon 7 of the AXIN2 gene, c.2013_2024del12 (p.Arg671_Pro674del), in two of 30 AA (7%), one of six ACC (17%), and the ACC H295R cell line. Immunohistochemistry revealed that tumors with AXIN2 genetic defects showed nuclear/cytoplasmic accumulation of ß-catenin, indicating the activation of Wnt signaling. In addition, the ACC and H295R cells with AXIN2 deletion (c.2013_2024del12) harbored p.Ser45del and p.Ser45Pro CTNNB1 mutations, respectively. Two single-nucleotide polymorphisms were identified in exon 7 of AXIN2, c.2351C>T in 2 AA, and one AIMAH and c.2342A>G in an AIMAH tissue. CONCLUSION: The present study reports, for the first time, that AXIN2 genetic defects may be found in adrenocortical tumors. However, the functional consequence of this genetic alteration remains to be determined.

Detection of somatic beta-catenin mutations in primary pigmented nodular adrenocortical disease (PPNAD).

BACKGROUND: Primary pigmented nodular adrenocortical disease (PPNAD) leads to Cushing syndrome (CS) and is often associated with Carney complex (CNC). Genetic alterations of the type 1-alpha regulatory subunit of cAMP-dependent protein kinase A (PRKAR1A) and phosphodiesterase 11A4 (PDE11A) genes have been found in PPNAD. Recent studies have demonstrated that beta-catenin mutations are frequent in adrenocortical adenomas and carcinomas and that the Wnt-signalling pathway is involved in PPNAD tumorigenesis. We hypothesized that adrenocortical adenomas that form in the context of PPNAD may harbour beta-catenin mutations. METHODS: We studied 18 patients with CS secondary to PPNAD who were screened for germline PRKAR1A and PDE11A mutations. Tumor DNA was extracted from pigmented adrenocortical adenoma and nodular adrenal hyperplasia. Mutation analysis of exons 3 and 5 of beta-catenin was performed using polymerase chain reaction and direct sequencing. Sections from formalin-fixed, paraffin-embedded tumour samples were studied by immunohistochemistry with an antibody against beta-catenin. RESULTS: Nine patients were carrying germline PRKAR1A mutations and one patient had a PDE11A mutation. We found somatic beta-catenin mutations in 2 of 18 patients (11%). In both cases, the mutations occurred in relatively large adenomas that had formed in the background of PPNAD. Tumor DNA analysis revealed a heterozygous ACC-to-GCC missense mutation in codon 41 (T41A) and a TCT-to-CCT missense mutation in codon 45 (S45P) of exon 3 of the beta-catenin gene that was confirmed at the cDNA level. There were no alterations in the DNA of PPNAD-adjacent tissues and lymphocytes from the patients, indicating somatic events. Immunohistochemistry showed nuclear accumulation of beta-catenin in more than 90% of cells in adenomatous tissue whereas no nuclear immunoreactivity was detected in adjacent PPNAD nodular cells. Nuclear translocation of beta-catenin protein in the PPNAD adenoma suggests activation of the Wnt-beta-catenin pathway in PPNAD. CONCLUSIONS: We report, for the first time, beta-catenin mutations in adenomas associated with PPNAD, further implicating Wnt-beta-catenin signalling in tumorigenesis linked to bilateral adrenal hyperplasias.

Frequent mutations of beta-catenin gene in sporadic secreting adrenocortical adenomas.

OBJECTIVE: Molecular alterations remain largely unknown in most sporadic adrenocortical tumours and hyperplasias. In our previous work, we demonstrated the differential expression of several Wnt/beta-catenin signalling-related genes implicated in ACTH-independent macronodular adrenal hyperplasias (AIMAH). To better understand the role of Wnt/beta-catenin signalling in adrenocortical tumours, we performed mutational analysis of the beta-catenin gene. METHODS: We studied 53 human adrenocortical samples (33 adenomas, 4 carcinomas, 13 AIMAH, 3 ACTH-dependent adrenal hyperplasias) and the human adrenocortical cancer cell line NCI-H295R. All samples were screened for somatic mutations in exons 3 and 5 of the beta-catenin gene. Eleven and six samples were analysed for beta-catenin protein expression by Western blotting and immunohistochemistry, respectively. RESULTS: No mutations were detected in adrenocortical carcinomas, AIMAH and ACTH-dependent hyperplasias. Genetic alterations were found in 5 (15%) out of 33 adenomas: three cortisol-secreting adenomas, one aldosterone-secreting adenoma and one nonfunctional adenoma. Two-point mutations occurred at serine residues of codons 37 and 45 (S37C and S45F). The remaining three tumours contained deletions of 6, 55 and 271 bp. H295R cells carry an activating S45P mutation. Western blot analysis of samples with 55- and 271-bp deletions showed an additional shorter and more intense band representing an accumulation of the mutated form of beta-catenin protein. In addition, cytoplasmic and/or nuclear accumulation of beta-catenin was observed in mutated adenomas by immunohistochemistry. CONCLUSIONS: Activating mutations of exon 3 of the beta-catenin gene are frequent in adrenocortical adenomas, and further characterization of the Wnt/beta-catenin signalling pathway should lead to a better understanding of adrenal tumourigenesis.

Isolation of human prostatic epithelial plasma membranes for proteomics using mirror image tissue banking of radical prostatectomy specimens.

PURPOSE: To isolate human prostatic epithelial plasma membranes for the identification of cell surface proteins in the therapeutic targeting of cancer cells while permitting the retrieval of banked samples for clinical purposes. EXPERIMENTAL DESIGN: Radical prostatectomies from 84 patients (median, 61 years; prostate-specific antigen, 5.9; 66% nonpalpable) were processed with alternate, mirror image slices submitted for histology and tissue banking. Benign and malignant foci were macrodissected from the banked sections using the pathologically mapped, mirror image histology sections as a guide. Epithelial plasma membranes were isolated using novel immunomagnetic purification and their purity was assessed. Tissue homogenates were probed by Western blot for malignant (AMACR) and benign (p63) markers to test the accuracy of this protocol. Selected banked tissue slices were retrieved, thawed, and compared pathologically to their corresponding routinely processed alternate slices. RESULTS: Plasma membrane preparations showed the enrichment of epithelial plasma membrane markers (prostate-specific membrane antigen and epithelial-specific antigen) with minimal marker expression from nonepithelial cells or intracellular organelles. Cancer homogenates showed up-regulated AMACR and down-regulated p63, whereas benign homogenates showed up-regulated p63 and down-regulated AMACR. There was 30% benign (p63+) contamination in cancer slices and <6% cancer (AMACR+) contamination in benign slices. Retrieved tissues showed the retention of immunoreactivity while their histology was always adequate for diagnosis. CONCLUSIONS: We have successfully isolated purified epithelial plasma membranes from benign and malignant human prostates and provided validation data for the accuracy of our protocol in a prostate-specific antigen-screened cohort. Our method also enabled the retrieval of banked tissues for clinical purposes with the retention of good histologic and immunohistochemical quality.