Análise da expressão da proteína PTEN em carcinoma papilar de tireoide

Abstract

PTEN (phosphatase and tensin homologue) is a tumor suppressor gene, located on chromosome 10q23.3. The gene negatively regulates the PI3K/Akt pathway, stimulating apoptosis and blocking the cell proliferation and cell growth. Decreased expression of PTEN protein leads to increased levels of Akt and inhibition of apoptosis and cell control mechanisms.. Despite PTEN mutations and deletions being rare in sporadic thyroid cancer, some authors found decreased expression of PTEN protein in sporadic follicular and, less frequently, papillary carcinomas and starting speculate the influence of epigenetic mechanisms like DNA hypermetilation in thyroid tumorigenesis, independent of histological type. The objective of this study was to correlate the PTEN protein expression with clinical, histological characteristics and tumor biological in sporadic papillary carcinomas, by immunohistochemical. Forty six pacientes submitted to total thyroidectomy with papillary thyroid cancer or folicular variant of papillary cancer were evaluated. We observed a notable hypoexpression of PTEN protein in majority of tumors compared to normal thyroid tissue, with statistic significance. However, we didn´t found correlation between the expression of PTEN and tumor size, aggressiveness or histological subtype (classic or follicular variant). Our findings suggest that PTEN can participate of papillary oncogenesis, but don´t confirm its role as predictor of aggressiveness. Additional molecular studies are necessary to establish the exact mechanism of PTEN´s inactivation.