Identification of the metabolic profile of cells with ectopic expression of PVALB and investigation of the molecular mechanism associated with its expression in Hürthle cell adenomas

Abstract

From the analysis performed by SAGE (Serial Analysis of Gene Expression) on benign and malignant thyroid samples, with subsequent validation by real-time PCR and immunohistochemistry, we found that the combined expression of five markers (PVALB, ITM1 and C1orf24, ARG2 and DDIT3), can distinguish benign and malignant thyroid lesions with high sensitivity and specificity. Among these, PVALB is specifically expressed in Hürthle cell adenomas, thus, it is a marker of benignity. To understand the role of PVALB in the pathogenesis of thyroid tumors, our group performed in vitro studies. We demonstrated, by the ectopic expression of PVALB in follicular thyroid carcinoma cell lines, that PVALB reduces the rates of free Ca2 + in cytoplasm and mitochondria. In addition, we found that PVALB reduced cell proliferation rate and induced cell death, probably via decreased GSK-3² and AKT phosphorylation and expression of proteins associated with reticulum stress (PERK). In addition, through the analysis by transmission electron microscopy, we observed that cells expressing PVALB have modifications in cell morphology. PVALB promoted an increase in cell size and number of mitochondrias. Finally, we observed that the expression of PVALB is correlated with the presence of calcium in the ACH samples, confirming our results obtained in vitro. These data together suggest an important role of PVALB in the acquisition of the phenotypic characteristics commonly observed in Hürthle cells and that PVALB can act as a tumor suppressor gene. In this project, we propose to investigate the mechanism associated to alteration of PVALB expression in Hürthle cell tumors. We aim to investigate whether these changes are due to some epigenetic mechanism (methylation) or by copy number variation. We propose also to analyze the metabolic profile associated with ectopic expression of PVALB in the cell lines of follicular thyroid carcinomas and, in this way, to identify possible metabolic pathways that may contribute to the pathogenesis of thyroid tumors. (AU)