A TFAP2C gene signature is predictive of outcome in HER2-positive breast cancer

The AP-2γ transcription factor, encoded by the TFAP2C gene, regulates the expression of estrogen receptor-alpha (ERα) and other genes associated with hormone response in luminal breast cancer. Little is known about the role of AP-2γ in other breast cancer subtypes. A subset of HER2⁺ breast cancers with amplification of the TFAP2C gene locus becomes addicted to AP-2γ. Herein, we sought to define AP-2γ gene targets in HER2⁺ breast cancer and identify genes accounting for physiologic effects of growth and invasiveness regulated by AP-2γ. ComparingHER2⁺ cell lines that demonstrated differential response to growth and invasiveness with knockdown of TFAP2C, we identified a set of 68 differentially expressed target genes. CDH5 and CDKN1A were among the genes differentially regulated by AP-2γ and that contributed to growth and invasiveness. Pathway analysis implicated the MAPK13/p38d and retinoic acid regulatory nodes, which were confirmed to display divergent responses in different HER2⁺ cancer lines. To confirm the clinical relevance of the genes identified, the AP-2γ gene signature was found to be highly predictive of outcome in patients with HER2⁺ breast cancer. We conclude that AP-2γ regulates a set of genes in HER2⁺ breast cancer that drive cancer growth and invasiveness. The AP-2γ gene signature predicts outcome of patients with HER2⁺ breast cancer and pathway analysis predicts that subsets of patients will respond to drugs that target theMAPK or retinoic acid pathways.