Abstract
Previously, we showed wild-type (WT) and mutant (mut) p53 differentially regulate reactive oxygen species (ROS) generation by NADPH oxidase-4 (NOX4): p53-WT suppresses TGFβ-induced NOX4, ROS and cell migration, whereas tumor-associated mut-p53 proteins enhance NOX4 expression and cell migration. Here, we extended our findings on the effects of p53 on NOX4 in several tumors and examined the basis of NOX4 transcriptional regulation by p53 and SMAD3. Statistical analysis of expression data from primary tumors available from The Cancer Genome Atlas (TCGA) detected correlations between mut-p53 and increased NOX4 expression. Furthermore, by altering p53 levels in cell culture models we showed several common tumor-associated mutant forms support TGFβ/SMAD3-dependent NOX4 expression. Deletion analysis revealed two critical SMAD3 binding elements (SBE) required for mut-p53-dependent NOX4 induction, whereas p53-WT caused dose-dependent suppression of NOX4 transcription. ChIP analysis revealed SMAD3 and p53-WT or mut-p53 associate with SBEs and p53 response elements in a TGFβ-dependent manner. Interestingly, the repressive effects of p53-WT on NOX4 were relieved by mutation of its transactivation domain or histone deacetylase (HDAC) inhibitor treatment. Overexpression of p300, a transcriptional co-regulator and histone acetyltransferase (HAT), enhanced p53-mediated NOX4 induction, whereas HAT-inactive p300 reduced NOX4 expression. Mut-p53 augmented TGFβ-stimulated histone acetylation within the NOX4 promoter. Finally, wound assays demonstrated NOX4 and p300 promote TGFβ/mut-p53-mediated cell migration. Our studies provide new insight into TGFβ/SMAD3 and mut-p53-mediated NOX4 induction involving epigenetic control of NOX4 in tumor cell migration, suggesting NOX4 is a potential therapeutic target to combat tumor progression and metastasis.
Highlights
The tumor suppressor gene TP53 is the most commonly mutated gene in human cancers
We found that p53-WT suppresses Transforming growth factor-β (TGFβ)-induced NADPH oxidase-4 (NOX4), reactive oxygen species (ROS) production, and cell migration, whereas tumor-associated mut-p53 proteins (R175H and R280K) enhance NOX4 expression and cell migration by a TGFβ/SMAD3-dependent mechanism
Tumor samples with mut-p53-Y220C correlated with reduced NOX4 expression indicating that not all DNA binding domain p53 mutants result in higher NOX4 expression
Summary
The tumor suppressor gene TP53 is the most commonly mutated gene in human cancers. 50% of all human cancers produce an inactive mutated tumor suppressor protein [1]. Tumor-associated p53 mutants have been shown to support an increase in cell proliferation, invasion, migration, angiogenesis, resistance to chemotherapeutic drugs, and tumor development in animal models [3,4,5,6,7]. Several reports have demonstrated that expression of GOF p53 mutants in p53-null cell models results in up-regulation of genes associated with cell survival, proliferation, and migration, whereas genes involved in cell cycle arrest and apoptosis are downregulated [8, 9]. The molecular mechanisms www.impactjournals.com/oncotarget underlying gene expression changes that support the GOF phenotypes are still unclear
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