p53 expression and mutation analysis of odontogenic cysts with and without dysplasia.
OBJECTIVE
Overexpression of p53 protein is well described in odontogenic cystic lesions (OCLs), including those with epithelial dysplasia; however, most p53 antibodies stain both wild-type and mutated p53 protein and may not reflect genotype. Direct sequencing of the p53 gene has not identified mutations in OCLs with dysplasia. The purpose of this study was to determine the molecular basis of p53 expression in several types of OCLs with and without dysplasia.


METHODS
The study material comprised 13 OCLs: odontogenic keratocyst (n = 5), orthokeratinized odontogenic cyst (n = 5), dentigerous cyst (n = 2), lateral periodontal cyst (n = 1), and unspecified developmental odontogenic cyst (UDOC) (n = 1). Five of these had features of mild or moderate epithelial dysplasia. One intraosseous squamous cell carcinoma (SCC) that was believed to have arisen from an antecedent dysplastic orthokeratinized OC was also included. Immunohistochemistry was performed using the DO7 monoclonal antibody that recognizes wild-type and mutated p53. DNA was extracted from microdissected tissue for all samples and exons 4 to 8 of the p53 gene direct sequenced.


RESULTS
In 4 of 5 OCLs with dysplasia there was strong nuclear staining of basal and suprabasal cells. In all cases without dysplasia, nuclear expression in basal cells was either negative or weak and was absent in suprabasal cell nuclei. A mutation in exon 6 of the p53 gene (E224D) was identified in both the dysplastic orthokeratinized OC and the subsequent intraosseous SCC.


CONCLUSIONS
OCLs with features of dysplasia show increased expression of p53 protein that does not reflect p53 mutational status. One dysplastic OC shared the same p53 mutation with a subsequent intraosseous SCC, indicating that p53 mutation may be associated with malignant transformation in this case.
University of Pacific Arthur A. Dugoni School of Dentistry, San Francisco, California 94115, USA. dcox@pacific.edu
Darren P
DP
Cox
D002294:Carcinoma, Squamous Cell / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D002467:Cell Nucleus / Q000473:pathology; D002471:Cell Transformation, Neoplastic / Q000235:genetics; D004252:DNA Mutational Analysis; D004847:Epithelial Cells / Q000473:pathology; D005260:Female; D015870:Gene Expression; D006801:Humans; D008336:Mandibular Diseases / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D008339:Mandibular Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D008875:Middle Aged; D009061:Mouth Mucosa / Q000473:pathology; D009807:Odontogenic Cysts / Q000235:genetics* / Q000378:metabolism* / Q000473:pathology; D011230:Precancerous Conditions / Q000235:genetics* / Q000473:pathology; D012189:Retrospective Studies; D016159:Tumor Suppressor Protein p53 / Q000096:biosynthesis / Q000235:genetics*
D016159:Tumor Suppressor Protein p53