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| Author(s): |
Andrea Cecilia Toscanini
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Faculdade de Medicina (FM/SBD) |
| Defense date: | 2005-03-11 |
| Examining board members: |
Daniel Giannella Neto;
Mari Cleide Sogayar;
José Gilberto Henriques Vieira;
Sandra Mara Ferreira Villares
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| Advisor: | Daniel Giannella Neto |
| Abstract | |
INTRODUCTION: The molecular mechanisms to the development of primary hyperparathyroidism (pHPT) are still unknown. Otherwise, several genes as PRAD1 and MEN-1 seem to play a role in parathyroid oncogenesis and are highly expressed in adenomas of pHPT patients when compared to normal glands. Another important data is the increased expression of HRPT2 in familiar and non-familiar parathyroid carcinomas. The distinction among hyperplasia, adenoma and carcinoma is a difficult task because there are limits in histopathologic parathyroid analysis in our days. This study has as main goal to identify genes that might help to distinguish hyperplasias from adenomas and both from carcinomas in pHPT patients. METHODS: Three techniques were employed: 1) clones from Human Cancer Genome Project (HCGP) fixed in membranes and hybridized with adenomas or carcinoma probes; 2) commercially available membranes (Atlas© cDNA Expression Array Human Oncogene/Tumor Suppressor, Human Cancer 1.2. BD Biosciences Clontech. Palo Alto, USA) which contain 190 and 1176 identified genes that were employed as substrate to hybridization with adenomas (n = 2) and carcinoma (n = 1) probes; 3) RDA technique (Representational Difference Analysis) in order to obtain differentially expressed cDNA fragments what in other steps were cloned and sequenced for further analysis. The genes, obtained from the three methods, that were differentially expressed between adenomas and carcinomas had their expression evaluated by RT-PCR in parathyroid tissues from patients bearing pHPT caused by hyperplasias, adenomas or carcinomas. RESULTS: genes chosen for PCR analysis: IRF-1, RAF, TIMP-3, NOTCH-2 and bFGF, whose expressions in the membrane were increased in adenomas and the genes IGF-1-R, PTK7 and RET, whose expression in the membrane were increased in carcinomas. Two genes had their differential expression confirmed. The IRF-1 had a decreased expression in the three situations of pHPT (hyperplasia, adenoma and carcinoma) when compared to its expression in the normal gland. The gene PTK7 confirmed its increased expression in samples obtained from carcinomas when compared to hyperplasias or to adenomas. DISCUSSION: The two genes whose differential expressions were confirmed, IRF-1 and PTK7, have not been described till this moment as coadjutants in the beginning or progression of parathyroid tumors. Our results associate the tumor suppressor gene IRF-1 to the origin of morphological and functional disturbs in parathyroid, because its expression in hyperplasia, adenoma or carcinoma of this gland were clearly lower in these conditions when compared to normal tissues, thus suggesting an important role of this gene in early steps of parathyroid oncogenesis. On the other hand, increased expression of PTK7 has already been described in malignant tumors of several tissues. Although their mechanisms of activation and action remain unknown, our results reinforce the literature data and suggest that this gene shares the molecular mechanisms of cell transformation in parathyroids (AU) | |