title: Molecular characterization of parathyroid tumors from two patients with hereditary colorectal cancer syndromes.
abstract: The tumor suppressor adenomatous polyposis coli (APC) has recently been implicated in parathyroid development. We here report clinical, histopathological and molecular investigations in parathyroid tumors arising in two patients; one familial adenomatous polyposis (FAP) syndrome patient carrying a constitutional APC mutation, and one Lynch syndrome patient demonstrating a germline MLH1 mutation as well as a non-classified, missense alteration of the APC gene. We sequenced the entire APC gene in tumor and constitutional DNA from both cases, assessed the levels of APC promoter 1A and 1B methylation by bisulfite Pyrosequencing analysis and performed immunohistochemistry for APC and parafibromin. In addition, copy number analysis regarding the APC gene on chromosome 5q21-22 was performed using qRT-PCR. Histopathological workup confirmed both tumors as parathyroid adenomas without signs of malignancy or atypia. No somatic mutations or copy number changes for the APC gene were discovered in the tumors; however, in both cases, the APC promoter 1A was hypermethylated while the APC promoter 1B was unmethylated. APC promoter 1B-specific mRNA and total APC mRNA levels were higher than in normal parathyroid samples. Immunohistochemical analyses revealed strong APC protein immunoreactivity and positive parafibromin expression in both parathyroid tumors. Absence of additional somatic APC mutations and copy number changes in addition to the positive APC immunoreactivity obtained suggest that the tumors arose without biallelic inactivation of the APC tumor suppressor gene. The finding of an unmethylated APC promoter 1B and high APC 1B mRNA levels could explain the maintained APC protein expression. Moreover, the findings of positive parafibromin and APC immunoreactivity as well as a low MIB-1 proliferation index and absence of histopathological features of malignancy/atypical adenoma indicate that the parathyroid adenomas arising in these patients did not harbor malignant potential.
authors.affiliation: Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Adam
authors.initials: A
authors.lastname: Andreasson
authors.forename: Luqman
authors.initials: L
authors.lastname: Sulaiman
authors.forename: Sónia
authors.initials: S
authors.lastname: do Vale
authors.forename: João Martin
authors.initials: JM
authors.lastname: Martins
authors.forename: Florbela
authors.initials: F
authors.lastname: Ferreira
authors.forename: Gabriel
authors.initials: G
authors.lastname: Miltenberger-Miltenyi
authors.forename: Lucas
authors.initials: L
authors.lastname: Batista
authors.forename: Felix
authors.initials: F
authors.lastname: Haglund
authors.forename: Erik
authors.initials: E
authors.lastname: Björck
authors.forename: Inga-Lena
authors.initials: IL
authors.lastname: Nilsson
authors.forename: Anders
authors.initials: A
authors.lastname: Höög
authors.forename: Catharina
authors.initials: C
authors.lastname: Larsson
authors.forename: C Christofer
authors.initials: CC
authors.lastname: Juhlin
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics; D000236:Adenoma / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D025601:Adenomatous Polyposis Coli Protein / Q000235:genetics* / Q000378:metabolism; D000368:Aged; D000369:Aged, 80 and over; D019175:DNA Methylation; D005260:Female; D018628:Gene Dosage; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008297:Male; D000070957:MutL Protein Homolog 1; D009154:Mutation; D009687:Nuclear Proteins / Q000235:genetics; D010282:Parathyroid Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D011401:Promoter Regions, Genetic; D025521:Tumor Suppressor Proteins / Q000378:metabolism
chemical_list: C555337:APC protein, human; D048868:Adaptor Proteins, Signal Transducing; D025601:Adenomatous Polyposis Coli Protein; C454900:CDC73 protein, human; C501486:MLH1 protein, human; D009687:Nuclear Proteins; D025521:Tumor Suppressor Proteins; D000070957:MutL Protein Homolog 1