A novel cell line derived from pleomorphic adenoma expresses MMP2, MMP9, TIMP1, TIMP2, and shows numeric chromosomal anomalies.

Pleomorphic adenoma is the most common salivary gland neoplasm, and it can be locally invasive, despite its slow growth. This study aimed to establish a novel cell line (AP-1) derived from a human pleomorphic adenoma sample to better understand local invasiveness of this tumor. AP-1 cell line was characterized by cell growth analysis, expression of epithelial and myoepithelial markers by immunofluorescence, electron microscopy, 3D cell culture assays, cytogenetic features and transcriptomic study. Expression of matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) was also analyzed by immunofluorescence and zymography. Furthermore, epithelial and myoepithelial markers, MMPs and TIMPs were studied in the tumor that originated the cell line. AP-1 cells showed neoplastic epithelial and myoepithelial markers, such as cytokeratins, vimentin, S100 protein and smooth-muscle actin. These molecules were also found in vivo, in the tumor that originated the cell line. MMPs and TIMPs were observed in vivo and in AP-1 cells. Growth curve showed that AP-1 exhibited a doubling time of 3.342 days. AP-1 cells grown inside Matrigel recapitulated tumor architecture. Different numerical and structural chromosomal anomalies were visualized in cytogenetic analysis. Transcriptomic analysis addressed expression of 7 target genes (VIM, TIMP2, MMP2, MMP9, TIMP1, ACTA2 e PLAG1). Results were compared to transcriptomic profile of non-neoplastic salivary gland cells (HSG). Only MMP9 was not expressed in both libraries, and VIM was expressed solely in AP-1 library. The major difference regarding gene expression level between AP-1 and HSG samples occurred for MMP2. This gene was 184 times more expressed in AP-1 cells. Our findings suggest that AP-1 cell line could be a useful model for further studies on pleomorphic adenoma biology.

Galectin-3 immunoprofile in adenoid cystic carcinoma and polymorphous low-grade adenocarcinoma of salivary glands.

Adenoid cystic carcinoma (ACC) and polymorphous low-grade adenocarcinoma (PLGA) are malignant neoplasms of salivary glands, which are similar in histologic patterns but very different in clinical behavior, treatment and prognosis. Galectin-3 is a multifunctional protein of a growing family of beta-galactoside-binding animal lectins, which is implicated in a variety of biological events such as tumor cell adhesion, proliferation, differentiation and angiogenesis. This protein was found to be implicated in cellular transformation and a correlation between its expression and cancer progression and metastasis has been described. The aim of this study was to determine the galectin-3 immunoprofile in 14 cases of ACC (2 cases of tubular subtype, 4 cases of solid subtype and 8 cases of cribriform subtype) and in 12 cases of PLGA with different histologic patterns, including lobular, tubular and cribriform aspects. Moreover, slides of normal salivary glands were included. In normal salivary glands there was strong nuclear and cytoplasmic staining for galectin-3 in ductal luminal cells. ACC showed specific staining in luminal cells mainly in the nuclei. In the tubular subtype of ACC, galectin-3 strongly stained luminal cells of the ductiform structures. The cribriform and solid subtypes showed a few positive luminal cells of small ducts present in the cribriform structures and in solid nests respectively. In the cases of PLGA, independent of the histologic architecture, all tumor cells revealed a positive cytoplasmic reaction. Galectin-3 expression seems to be related to cell differentiation more than to tumor progression and prognosis in the neoplasms studied.

Metallothionein immunostaining in adenoid cystic carcinomas of the salivary glands.

Metallothionein (MT) is a protein that has been studied in several tumors as a prognostic factor and as a potential myoepithelial cell marker in breast cancer. The aims of this study were to assess the immunohistochemical staining of MT in adenoid cystic carcinomas of the salivary glands (ACC), and to analyze possible morphological and quantitative variations among the solid, cribriform, and tubular histological subtypes. MT was investigated in 15 cases of ACC using the immunohistochemical technique. All of the cases expressed the MT antigen. This expression was noteworthy in cells depicting myoepithelial differentiation. ACC with predominant tubular pattern presented a significantly lower mean index of MT immunopositivity than did solid or cribriform subtypes, while these two latter groups did not differ in terms of MT expression. Our results suggest that MT may be an important tool for immunolocalization of myoepithelial tumor cells in salivary gland neoplasms.