Abstract
BackgroundSalivary gland cancer (SGC) is one of the common malignancies of the head and neck area. It develops in the minor and major salivary glands and sometimes metastasizes to other organs, particularly to the lungs. Inhibitors of differentiation (Id) proteins are negative regulators of basic helix-loop-helix transcription factors that control malignant cell behavior and tumor aggressiveness in many tissues. In this study, our goal was to determine the potential role of Id proteins, particularly Id1, during human SGC cell progression.MethodsWe first determined the expression levels of Id1 and Id2 in four SGC cell lines: two adenocarcinoma of the salivary gland (HSG and HSY) and two adenoid cystic carcinoma (ACC2 and ACCM) cell lines. We then used constructs that expressed antisense cDNAs to Id1 or Id2 to knockdown the expression of these proteins in cell lines where they were highly expressed, and determined the effects of the knockdown on cell proliferation, migration and invasion.ResultsId1 mRNA and protein were detectable in all cell lines, and expression of Id2 was variable, from absent to high. The ACC2 and ACCM cell lines expressed both Id1 and Id2, but Id1 was expressed at a higher level in the more aggressive ACCM cell line in comparison toACC2 cells as confirmed by Id1 promoter-reporter assays. We therefore focused on the ACCM cells for the remainder of the study. We found that proliferation and invasiveness of ACCM cells were strongly reduced after Id1 knockdown whereas Id2 suppression had only a slight effect. Results of scratch and colony formation assays also confirmed that ACCM cell aggressiveness was significantly reduced upon Id1 knockdown. Finally, this knockdown resulted in reduced c-myc and enhanced cyclin-dependent kinase inhibitor p21 expression.ConclusionsThese results demonstrate that Id1 plays an important role in the control of human SGC cell aggressiveness and suggest a potential role as a marker of diagnosis, prognosis and progression of SGCs. Id1 suppression could represent a novel and effective approach for the treatment of salivary gland cancer.
Highlights
Salivary gland cancer (SGC) is one of the common malignancies of the head and neck area
HSG cells were established from an adenocarcinoma of the submandibular gland [17], HSY cells were established from an adenocarcinoma [18], ACC2 cells were established from an adenoid cystic carcinoma, and ACCM cells were a subpopulation of ACC2 with a highly aggressive phenotype [19]
Western blot analysis demonstrated that ACCM cells, an aggressive sub-clone of ACC2 cells, had the strongest expression of Id1, whereas Id2 was expressed at similar levels in ACC2 and ACCM cells, and almost undetectable in HSG and HSY cells (Figure 1)
Summary
Salivary gland cancer (SGC) is one of the common malignancies of the head and neck area. It develops in the minor and major salivary glands and sometimes metastasizes to other organs, to the lungs. Inhibitors of differentiation (Id) proteins are negative regulators of basic helix-loop-helix transcription factors that control malignant cell behavior and tumor aggressiveness in many tissues. Id proteins are a class of helix-loop-helix (HLH) transcriptional regulators Constitutive expression of these proteins inhibits the differentiation of various cell types through their interaction with basic helix-loop-helix (bHLH) proteins [9,10]. BHLH proteins act as obligate dimers binding DNA through composite basic domains to regulate the transcription of target genes containing E-boxes (CANNTG) in their promoters. Id proteins are dominant negative regulators of bHLH function [9,11]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
