ABSTRACT
Aberrant Wnt/ß-catenin signaling is implicated in tumorigenesis and the progression of human colorectal cancers, and mutations in the components of the Wnt/ß-catenin signaling pathway are observed in the majority of patients. Therefore, extensive studies on the Wnt signaling pathway and its target genes are crucial to understand the molecular events of tumorigenesis and develop an efficacious therapy. In this study, we showed that the stress response gene ATF3 is transcriptionally activated by the binding of ß-catenin and TCF4 to the redundant TCF4 site at the proximal promoter region of the ATF3 gene, indicating that ATF3 is a direct target of the Wnt/ß-catenin pathway. The loss of function or overexpression studies showed that ATF3 inhibited the migration or invasion of HCT116 cells. The expression of some MMP and TIMP genes and the ratio of MMP2/9 to TIMP3/4 mRNAs was differentially regulated by ATF3. Therefore, though ATF3 is activated downstream of the Wnt/ß-catenin pathway, it acts as a negative regulator of the migration and invasion of HCT116 human colon cancer cells exhibiting aberrant Wnt/ß-catenin activity. ATF3 is a candidate biomarker and target for human colorectal cancer treatment and prevention.
Subject(s)
Activating Transcription Factor 3/genetics , Biomarkers, Tumor/genetics , Carcinogenesis/genetics , Colorectal Neoplasms/genetics , Neoplasm Invasiveness/genetics , Cell Movement/genetics , Cell Proliferation/genetics , Colorectal Neoplasms/pathology , Gene Expression Regulation, Neoplastic , HCT116 Cells , Humans , Matrix Metalloproteinase 2/genetics , Matrix Metalloproteinase 9/genetics , Neoplasm Invasiveness/pathology , Protein Binding , Tissue Inhibitor of Metalloproteinase-3/genetics , Transcription Factor 4/genetics , Wnt Signaling Pathway/genetics , beta Catenin/geneticsABSTRACT
Autophagy is a highly conserved pathway for the degradation and recycling of long-lived proteins and cytoplasmic organelles. Similar to apoptosis, autophagy is a critical regulatory mechanism for determining cellular fate and various pathophysiological conditions in metazoans. So far, the systematic analysis of the expression patterns and transcriptional regulation of autophagy-related (ATG) genes has remained incompletely defined. In this study, we used RT-PCR to analyze the expression patterns of 26 human ATG genes simultaneously using cDNA derived from different adult and fetal tissues. As a result, we observed a characteristic ubiquitous expression pattern for all the genes except for ATG2A, ATG9B, and WIPI2. In particular, ATG2A was the only upregulated gene in the etoposide-induced apoptosis of HeLa cells. ATG2A mRNA was also upregulated by doxorubicin. Furthermore, we demonstrated that 13 out of 23 human ATG gene promoters were regulated by the transcription factor E2F1 in HeLa cells, indicating that these constructs could be useful for examining how the autophagy pathway is involved in other cellular phenomena, such as apoptosis evoked by various stimuli. Taken together, these results suggest that autophagy might be regulated at both the transcriptional level and the post-translational level.
