ABSTRACT
The epithelial-mesenchymal transition (EMT) is activated in cancer cells by ZEB1, a member of the zinc finger/homeodomain family of transcriptional repressors. The mucin 1 (MUC1) heterodimeric protein is aberrantly overexpressed in human carcinoma cells. The present studies in breast cancer cells demonstrate that the oncogenic MUC1-C subunit induces expression of ZEB1 by a NF-κB (nuclear factor kappa B) p65-dependent mechanism. MUC1-C occupies the ZEB1 promoter with NF-κB p65 and thereby promotes ZEB1 transcription. In turn, ZEB1 associates with MUC1-C and the ZEB1/MUC1-C complex contributes to the transcriptional suppression of miR-200c, an inducer of epithelial differentiation. The co-ordinate upregulation of ZEB1 and suppression of miR-200c has been linked to the induction of EMT. In concert with the effects of MUC1-C on ZEB1 and miR-200c, we show that MUC1-C induces EMT and cellular invasion by a ZEB1-mediated mechanism. These findings indicate that (i) MUC1-C activates ZEB1 and suppresses miR-200c with the induction of EMT and (ii) targeting MUC1-C could be an effective approach for the treatment of breast and possibly other types of cancers that develop EMT properties.
Subject(s)
Breast Neoplasms/metabolism , Homeodomain Proteins/metabolism , MicroRNAs/metabolism , Mucin-1/metabolism , Transcription Factors/metabolism , Breast Neoplasms/genetics , Breast Neoplasms/pathology , Cell Line, Tumor , Epithelial-Mesenchymal Transition , Homeodomain Proteins/genetics , Humans , MCF-7 Cells , MicroRNAs/genetics , Mucin-1/genetics , Transcription Factors/genetics , Transfection , Up-Regulation , Zinc Finger E-box-Binding Homeobox 1ABSTRACT
Patients with HER2-positive breast cancer often exhibit intrinsic or acquired resistance to trastuzumab treatment. The transmembrane mucin 1 (MUC1) oncoprotein is aberrantly overexpressed in breast cancer cells and associates with HER2. The present studies demonstrate that silencing MUC1 C-terminal subunit (MUC1-C) in HER2-overexpressing SKBR3 and BT474 breast cancer cells results in the downregulation of constitutive HER2 activation. Moreover, treatment with the MUC1-C inhibitor, GO-203, was associated with disruption of MUC1-C/HER2 complexes and decreases in tyrosine-phosphorylated HER2 (p-HER2) levels. In studies of trastuzumab-resistant SKBR3R and BT474R cells, we found that the association between MUC1-C and HER2 is markedly increased (â¼20-fold) as compared with that in sensitive cells. In addition, silencing MUC1-C in the trastuzumab-resistant cells or treatment with GO-203 decreased p-HER2 and AKT activation. Moreover, targeting MUC1-C was associated with the downregulation of phospho-p27 and cyclin E, which confer trastuzumab resistance. Consistent with these results, targeting MUC1-C inhibited the growth and clonogenic survival of both trastuzumab-resistant cells. Our results further demonstrate that silencing MUC1-C reverses resistance to trastuzumab and that the combination of GO-203 and trastuzumab is highly synergistic. These findings indicate that MUC1-C contributes to constitutive activation of the HER2 pathway and that targeting MUC1-C represents a potential approach to abrogate trastuzumab resistance.
Subject(s)
Antibodies, Monoclonal, Humanized/pharmacology , Breast Neoplasms/genetics , Drug Resistance, Neoplasm/genetics , Mucin-1/genetics , Receptor, ErbB-2/metabolism , Animals , Antineoplastic Agents/pharmacology , Breast Neoplasms/drug therapy , Cell Line, Tumor , Cell Proliferation/drug effects , Cyclin E/biosynthesis , Cyclin-Dependent Kinase Inhibitor p27/biosynthesis , Down-Regulation , Female , Gene Expression Regulation, Neoplastic , Humans , Lapatinib , Mice , Mice, Inbred BALB C , Mice, Nude , Mucin-1/biosynthesis , Mucin-1/metabolism , Peptides/pharmacology , Phosphorylation , Proto-Oncogene Proteins c-akt/biosynthesis , Quinazolines/pharmacology , RNA Interference , RNA, Small Interfering , Receptor, ErbB-2/biosynthesis , Trastuzumab , Xenograft Model Antitumor AssaysABSTRACT
Education in fabricating single-tooth fixed prostheses and multi-teeth fixed prostheses is an important component of the dental curriculum. To explore the opinion of dental students on this component of the curriculum, a web-based survey was carried out among the students of the 3 dental schools in the Netherlands. The 389 completed questionnaires revealed that the education in fabricating single-tooth fixed prostheses and multi-teeth fixed prostheses started in different years of study at the 3 dental schools. Another striking difference is that the methods of preparation and the choice of materials for single-tooth fixed prostheses and multi-teeth fixed prostheses in the pre-clinical practicum in the programmes was not the same. The students of the 3 dental schools seemed to have a reasonably positive opinion of their preclinical training preparation for treating patients. The opinions of the Nijmegen Dental School students were significantly more positive than the opinions of the students at the 2 other dental schools.
