Expression of Pax-8, p53 and bcl-2 in human benign and malignant thyroid diseases.
BACKGROUND
Immunohistochemical expression of the transcription factor Pax-8 in human thyroid diseases has never been investigated. The relationship between Pax-8, bcl-2 and p53 in thyroid neoplasms is also matter of interest.


METHODS
Seventy-three thyroid tissue samples were evaluated for the expression of Pax-8, p53 and bcl-2 using the immunoperoxidase technique. The series included 11 follicular adenomas, 11 goitres, 23 papillary carcinomas, 16 follicular carcinomas, 6 undifferentiated carcinomas and 6 medullary carcinomas.


RESULTS
The percentage of Pax-8 positive cells ranged from 14.9 to 27.1% and 10.1 to 39% in goitres and follicular adenomas, respectively. Among differentiated carcinomas, follicular histotype showed a Pax-8 immunoreactivity ranging from 0 to 26.5% of the neoplastic cells whereas in papillary carcinomas the percentage of positive cells ranged from 0 to 16.8%. None out of the six undifferentiated carcinomas showed Pax-8 immunoreactivity. The same negative pattern was noticed in medullary carcinomas. A statistically significant difference in Pax-8 expression was observed between non-malignant and malignant diseases (p < 0.0001). A different reactivity for Pax-8 was also noticed between differentiated carcinomas and undifferentiated carcinomas (p = 0.07). None of the benign tissues stained for p53 whereas among malignant specimens different percentages of p53 expression were observed with all undifferentiated carcinomas expressing the highest positivity (range 24.1-88.6%). Finally, when a combined analysis of bcl-2 and Pax-8 reactivity was carried out, some carcinomas proved to be Pax-8 negative and bcl-2 positive whereas others showed a similar immunoreactive pattern for both Pax-8 and bcl-2.


CONCLUSIONS
Pax-8 is mainly expressed in benign rather than in malignant thyroid diseases and, among neoplasms, differentiated carcinomas express Pax-8 more frequently than undifferentiated carcinomas. An inverse pattern was observed for p53. Bcl-2 seems to be partially related to Pax-8 expression. However, a Pax-8 independent bcl-2 expression is also evident.
Puglisi
F
F
Institute of Clinical Oncology, University of Udine, Italy. fabio.puglisi@med.uniud.it
Cesselli
D
D
Damante
G
G
Pellizzari
L
L
Beltrami
C A
CA
Di Loreto
C
C
D018263:Adenocarcinoma, Follicular / Q000737:chemistry / Q000473:pathology; D000236:Adenoma / Q000737:chemistry / Q000473:pathology; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002277:Carcinoma / Q000737:chemistry / Q000473:pathology; D018276:Carcinoma, Medullary / Q000737:chemistry / Q000473:pathology; D002291:Carcinoma, Papillary / Q000737:chemistry / Q000473:pathology; D002454:Cell Differentiation; D004268:DNA-Binding Proteins / Q000032:analysis*; D005260:Female; D006801:Humans; D007124:Immunoenzyme Techniques; D008297:Male; D008875:Middle Aged; D009363:Neoplasm Proteins / Q000032:analysis; D009687:Nuclear Proteins; D000072636:PAX8 Transcription Factor; D051761:Paired Box Transcription Factors; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000032:analysis*; D013959:Thyroid Diseases / Q000378:metabolism* / Q000473:pathology; D013964:Thyroid Neoplasms / Q000737:chemistry / Q000473:pathology; D015534:Trans-Activators / Q000032:analysis*; D016159:Tumor Suppressor Protein p53 / Q000032:analysis*
D004268:DNA-Binding Proteins; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D000072636:PAX8 Transcription Factor; C083325:PAX8 protein, human; D051761:Paired Box Transcription Factors; D019253:Proto-Oncogene Proteins c-bcl-2; D015534:Trans-Activators; D016159:Tumor Suppressor Protein p53