Transcription factor AP2C (TFAP2C) is believed to be involved in breast cancer carcinogenesis. However, the molecular mechanisms of regulating its trans-activation activity are not well understood. One of the potential mechanisms is through p53-mediated regulation. Using ChIP-seq analysis to map the TFAP2C occupancy across the genome, we found that the introduction of p53 to HCT 116 p53 -/- colon cancer cell line significantly augments TFAP2C occupancy on the promoter regions of a group of genes. Of these, six genes were further investigated. First, TFAP2C binding sites were identified in the center of ChIP-seq peaks on the promoters of the six genes and these were verified by gel shift assays. One of these genes, MUC1, was then determined to be activated by TFAP2C in MCF-7 breast cancer cell line. Subsequently, MUC1 was selected as the model target gene to elucidate the mechanism for p53-mediated enhancement of TFAP2C occupancy. We hypothesized that DNA methylation of the MUC1 promoter is altered by p53, leading to the increased TFAP2C occupancy to its TFBS on MUC1 promoter. To examine this, CpG methylation assay was performed. The result showed the DNA methylation of MUC1 promoter region remains identical with or without over-expression of p53 in HCT 116 p53 -/- cell line. From these studies, I conclude that 1) introduction of p53 augments TFAP2C binding on specific gene targets; 2) MUC1 gene is activated by TFAP2C and two TFAP2C binding sites were verified; 3) promoter DNA methylation does not explain the increased occupancy of TFAP2C on MUC1 promoter.

Breast cancer is a heterogeneous disease with multiple phenotypes that specify both treatment options and prognosis. The Luminal A-type breast cancers, characterized by high levels of estrogen receptor (ER) expression and transcriptional activity, have a stable of hormone-related treatment options and a favorable prognosis. Recent efforts to identify mechanisms governing the Luminal A phenotype have identified transcription factor activator protein 2C (TFAP2C) as a critical regulator of both ER and ER-associated gene expression, making it a prime target for manipulation in breast cancer therapy. To that end, we sought to establish specific contributions of TFAP2C in both normal development and cancer progression, with the overarching hypothesis that TFAP2C is an integral transcription factor in maintaining a luminal differentiation and expression pattern in human breast cancer. To address this, we utilized several parallel approaches to identify potential TFAP2C-related contributions to carcinogenesis. In the first approach, we identified that tissue-specific abrogation of the mouse homolog TCFAP2C in mammary epithelium produced a reduction in luminal populations and a concomitant increase in basal populations, producing mild phenotypic alterations in gland structure. In the second, we stably manipulated TFAP2C expression in the established Luminal A model cell line MCF-7, establishing that TFAP2C loss promotes a loss of luminal differentiation characteristics and a gain of basal / mesenchymal traits, mirroring the results found in the mouse model. As a final approach, we examined the role of a TFAP2C target gene, manganese superoxide dismutase (MnSOD), in modulating redox biological and epigenetic parameters that may contribute to carcinogenesis. We found that loss of MnSOD in the murine liver, chosen because of its utility as a model system, promoted subtle changes in the redox buffering capacity and identified preliminary changes in the epigenome, suggesting that MnSOD modulation by TFAP2C could play a role in cancer development. Overall, these results further establish a role of TFAP2C in the genesis of Luminal A breast cancer, and serve as a foundation for more comprehensive future work evaluating specific contributions in carcinogenesis.