ABSTRACT
Oral squamous cell carcinoma (OSCC) patients generally have a poor prognosis, because of the invasive nature of these tumors. In comparing transcription profiles between OSCC tumors with a more invasive (worst pattern of tumor invasion 5) versus a less invasive (worst pattern of tumor invasion 3) pattern of invasion, we identified a total of 97 genes that were overexpressed at least 1.5-fold in the more invasive tumor subtype. The most functionally relevant genes were assessed using in vitro invasion assays with an OSCC cell line (UM-SCC-1). Individual siRNA knockdown of 15 of these 45 genes resulted in significant reductions in tumor cell invasion compared to a nontargeting siRNA control. One gene whose knockdown had a strong effect on invasion corresponded to apolipoprotein E (APOE). Both matrix degradation and the number of mature invadopodia were significantly decreased with APOE knockdown. APOE knockdown also resulted in increased cellular cholesterol, consistent with APOE's role in regulating cholesterol efflux. APOE knockdown resulted in decreased levels of phospho-extracellular signal-regulated kinase 1/2, phospho-c-Jun N-terminal kinase, and phospho-cJun, as well as decreased activator protein 1 (AP-1) activity. Expression of matrix metalloproteinase 7 (MMP7), an AP-1 target, was also significantly decreased. Our findings suggest that APOE protein plays a significant role in OSCC tumor invasion because of its effects on cellular cholesterol and subsequent effects on cell signaling and AP-1 activity, leading to changes in the expression of invasion-related proteins, including MMP7.
Subject(s)
Apolipoproteins E/metabolism , Carcinoma, Squamous Cell/pathology , Mouth Neoplasms/pathology , Apolipoproteins E/genetics , Carcinoma, Squamous Cell/genetics , Cell Line, Tumor , Cholesterol/metabolism , Extracellular Matrix/metabolism , Extracellular Signal-Regulated MAP Kinases/metabolism , Gene Expression Regulation, Neoplastic , Gene Knockdown Techniques , Genome, Human , Humans , JNK Mitogen-Activated Protein Kinases/metabolism , Matrix Metalloproteinase 7/metabolism , Models, Biological , Mouth Neoplasms/genetics , Neoplasm Invasiveness , Phosphorylation , Podosomes/metabolism , Proto-Oncogene Proteins c-jun/metabolism , RNA, Messenger/genetics , RNA, Messenger/metabolism , RNA, Small Interfering/metabolism , Signal Transduction/genetics , Transcription Factor AP-1/metabolism , Transcriptome/geneticsABSTRACT
CONTEXT: The highly invasive properties demonstrated by head and neck squamous cell carcinoma (HNSCC) are often associated with locoregional recurrence and lymph node metastasis in patients and is a key factor leading to an expected 5-year survival rate of approximately 50% for patients with advanced disease. It is important to understand the features and mediators of HNSCC invasion so that new treatment approaches can be developed. OBJECTIVES: To provide an overview of the characteristics, mediators, and mechanisms of HNSCC invasion. DATA SOURCES: A literature review of peer-reviewed articles in PubMed on HNSCC invasion. CONCLUSIONS: Histologic features of HNSCC tumors can help predict prognosis and influence clinical treatment decisions. Cell surface receptors, signaling pathways, proteases, invadopodia function, epithelial-mesenchymal transition, microRNAs, and tumor microenvironment are all involved in the regulation of the invasive behavior of HNSCC cells. Identifying effective HNSCC invasion inhibitors has the potential to improve outcomes for patients by reducing the rate of spread and increasing responsiveness to chemoradiation.
Subject(s)
Carcinoma, Squamous Cell/pathology , Head and Neck Neoplasms/pathology , Carcinoma, Squamous Cell/genetics , Carcinoma, Squamous Cell/therapy , Chemoradiotherapy/methods , Epithelial-Mesenchymal Transition , Head and Neck Neoplasms/genetics , Head and Neck Neoplasms/therapy , Humans , Lymphatic Metastasis , MicroRNAs/genetics , Neoplasm Invasiveness , Signal Transduction , Treatment OutcomeABSTRACT
In Escherichia coli, cytosine DNA methylation is catalyzed by the DNA cytosine methyltransferase (Dcm) protein and occurs at the second cytosine in the sequence 5'CCWGG3'. Although the presence of cytosine DNA methylation was reported over 35 years ago, the biological role of 5-methylcytosine in E. coli remains unclear. To gain insight into the role of cytosine DNA methylation in E. coli, we (1) screened the 72 strains of the ECOR collection and 90 recently isolated environmental samples for the presence of the full-length dcm gene using the polymerase chain reaction; (2) examined the same strains for the presence of 5-methylcytosine at 5'CCWGG3' sites using a restriction enzyme isoschizomer digestion assay; and (3) quantified the levels of 5-methyl-2'-deoxycytidine in selected strains using liquid chromatography tandem mass spectrometry. Dcm-mediated cytosine DNA methylation is conserved in all 162 strains examined, and the level of 5-methylcytosine ranges from 0.86% to 1.30% of the cytosines. We also demonstrate that Dcm reduces the expression of ribosomal protein genes during stationary phase, and this may explain the highly conserved nature of this DNA modification pathway.
Subject(s)
DNA (Cytosine-5-)-Methyltransferases/genetics , DNA (Cytosine-5-)-Methyltransferases/metabolism , Escherichia coli/enzymology , Escherichia coli/genetics , 5-Methylcytosine/analysis , Chromatography, Liquid , Conserved Sequence , DNA, Bacterial/chemistry , DNA, Bacterial/genetics , Escherichia coli/chemistry , Gene Expression Regulation, Bacterial , Polymerase Chain Reaction , Ribosomal Proteins/biosynthesis , Tandem Mass SpectrometryABSTRACT
It is currently unclear if there are modified DNA bases in Trypanosoma brucei other than J-base. We identify herein a cytosine-5 DNA methyltransferase gene and report the presence and location of 5-methylcytosine in genomic DNA. Our data demonstrate that African trypanosomes contain a functional cytosine DNA methylation pathway.