ABSTRACT
OBJECTIVE: Adrenocortical carcinoma (ACC) is a rare neoplasm with poor prognosis. Discerning ACCs from benign adenomas histologically may be difficult if invasion into surrounding tissues or metastases are missing. DESIGN: In order to establish molecular markers for malignancy, we analyzed seven normal adrenals, three massive macronodular ACTH-independent adrenocortical hyperplasias (MMAHs), 30 adrenocortical adenomas (ACAs) and ten ACCs. METHODS: All tissues were studied for the presence of alterations in the p53 tumor suppressor gene using the PAb 1801 antibody, which detects mutant p53 protein and the pYNZ22 microsatellite marker to show loss of heterozygosity (LOH) at 17p, for expression of the proliferation-associated antigen Ki67 using the MIB1 antibody, for the rate of apoptotic tumor cells with the TdT-mediated dUTP biotin nick end labeling (TUNEL) method, and for LOH of 11q13 (menin gene locus) with the D11S956 microsatellite marker. RESULTS: 0/3 MMAH, 1/28 ACA and 3/10 ACC revealed immunopositive staining for p53. LOH for pYNZ22 was observed in 1/3 MMAH, 1/23 informative ACA and 6/6 informative ACC. The rate of apoptotic cells was significantly higher in ACC (P<0.0001 by ANOVA) than in ACA but there was some overlap between groups. The Ki67 index (% immunopositive cells) was 1.9+/-1.30% (mean+/-s.d.) in normal adrenals, 3.47+/-1.37% in MMAH, and 2.11+/-1.01% in ACA. ACC had the highest Ki67 index of 11.94+/-7.58% distinguishing all ACC from the ACA and MMAH studied with a cut-off level of 5%. LOH for 11q13 was detected in 2/3 MMAH, 5/26 ACA and 6/8 ACC. CONCLUSIONS: We conclude that a Ki67 index above 5% is a sensitive and specific indicator of ACC and may be useful in the differentiation of adenomas from carcinomas.
Subject(s)
Adrenal Cortex Neoplasms/diagnosis , Adrenal Cortex Neoplasms/genetics , Genetic Markers , Adenoma/diagnosis , Adolescent , Adrenal Cortex/pathology , Adult , Aged , Apoptosis , Carcinoma/diagnosis , Child , Child, Preschool , Diagnosis, Differential , Gene Expression , Genes, p53/genetics , Humans , Hyperplasia , Infant , Ki-67 Antigen/analysis , Loss of Heterozygosity , Middle Aged , Multiple Endocrine Neoplasia Type 1/genetics , Prognosis , Tumor Suppressor Protein p53/analysisABSTRACT
Mutations in the p53 tumor suppressor gene are frequently present in human cancers but have rarely been described in benign tumors. We previously reported mutations in the "hot spots" between exons 5-8 of the p53 gene in adrenocortical carcinomas but not in adenomas. Recently, a previously unknown hot spot in exon 4 of the p53 gene was described in adrenal adenomas and pheochromocytomas of Taiwanese patients. We, therefore, investigated whether these mutations are also present in Caucasian patients from the U.S. and Europe. We analyzed tumor tissue of 12 aldosterone-producing adenomas, 7 cortisol-producing adenomas, and 6 pheochromocytomas. Overexpression of the p53 protein was investigated by immunohistochemistry. Point mutations within exon 4 were identified by polymerase chain reaction (PCR) amplification and direct sequencing of the PCR product. The pYNZ22 microsatellite located on chromosome 17p, close to the p53 gene, was used to screen for allelic loss (LOH) of the p53 gene. Overexpression of p53 was not identified in any of the adenomas and pheochromocytomas. Point mutations within exon 4 were found in 0/25 tumors. LOH was present in 1/13 informative adenomas and 0/2 informative pheochromocytomas. We conclude that p53 mutations do not play a major role in the tumorigenesis of adrenal adenomas and pheochromocytomas of Caucasian patients. Thus, ethnic and environmental factors may be responsible for the mutational spectrum found in Taiwanese patients.
Subject(s)
Adrenal Gland Neoplasms/genetics , Exons , Genes, p53 , Mutation , White People/genetics , Adenoma/genetics , Adenoma/metabolism , Adolescent , Adrenal Cortex Neoplasms/genetics , Adrenal Cortex Neoplasms/metabolism , Adrenal Gland Neoplasms/metabolism , Adult , Aged , Aldosterone/biosynthesis , Carcinoma/genetics , Child , Child, Preschool , DNA Primers , Humans , Hydrocortisone/biosynthesis , Infant , Middle Aged , Pheochromocytoma/genetics , TaiwanABSTRACT
The ctaBCDEF genes coding for cytochrome c oxidase were found to reside adjacent to a regulatory gene ctaA at 127 degrees on the Bacillus subtilis chromosome. The structural genes for subunits I and II, ctaD and ctaC, were deleted by gene-replacement using a phleomycin-resistance marker. The mutant was unable to oxidize N,N,N',N'-tetramethyl-p-phenylene-diamine and oxidized cytochrome c at a significantly lower rate. Absorption spectra of the mutant and wild-type membranes confirmed the presence of two haem A-containing enzymes in B. subtilis. Another mutant, with a spontaneous deletion upstream from ctaC, was found to express neither of these enzymes. Radioactive haem-labelling was used to identify subunit II, which contains a haem C, and cytochrome c-550 among the membrane-bound c-type cytochromes of B. subtilis.
