A <i>TFAP2C</i> Gene Signature Is Predictive of Outcome in HER2-Positive Breast Cancer

Abstract

The AP-2γ transcription factor, encoded by the <i>TFAP2C</i> 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 <i>TFAP2C</i> 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. Comparing HER2⁺ cell lines that demonstrated differential response to growth and invasiveness with knockdown of <i>TFAP2C</i>, we identified a set of 68 differentially expressed target genes. <i>CDH5</i> and <i>CDKN1A</i> were among the genes differentially regulated by AP-2γ and that contributed to growth and invasiveness. Pathway analysis implicated the <i>MAPK13</i>/p38δ 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 the MAPK or retinoic acid pathways. IMPLICATIONS: A set of genes regulated by AP-2γ in HER2⁺ breast cancer that drive proliferation and invasion were identified and provided a gene signature that is predictive of outcome in HER2⁺ breast cancer.