ABSTRACT
BACKGROUND: HER2 plays a critical role in tumourigenesis and is associated with poor prognosis of patients with HER2-positive breast cancers. Although anti-HER2 drugs are beneficial for treating breast cancer, de novo, or acquired resistance often develops. Epigenetic factors are increasingly targeted for therapy; however, such mechanisms that interact with HER2 signalling are poorly understood. METHODS: RNA sequencing was performed to identify PHF8 targets downstream of HER2 signalling. CHIP-qPCR were used to investigate how PHF8 regulates HER2 transcription. ELISA determined cytokine secretion. Cell-based assay revealed a feed forward loop in HER2 signalling and then evaluated in vivo. FINDINGS: We report the synergistic interplay between histone demethylase PHF8 and HER2 signalling. Specifically, PHF8 levels were elevated in HER2-positive breast cancers and upregulated by HER2. PHF8 functioned as a coactivator that regulated the expression of HER2, markers of the HER2-driven epithelial-to-mesenchymal transition and cytokines. The HER2-PHF8-IL-6 regulatory axis was active in cell lines and in newly established MMTV-Her2/MMTV-Cre/Phf8fl°x/fl°x mouse models, which revealed the oncogenic function of Phf8 in breast cancer for the first time. Further, the PHF8-IL-6 axis contributed to the resistance to trastuzumab in vitro and may play a critical role in the infiltration of T cells in HER2-driven breast cancers. INTERPRETATION: These findings provided informative mechanistic insight into the potential application of PHF8 inhibitors to overcome resistance to anti-HER2 therapies. FUNDING: This work was supported by Carver Trust Young Investigator Award (01-224 to H.H.Q); and a Breast Cancer Research Award (to H.H.Q.).
Subject(s)
Breast Neoplasms/metabolism , Breast Neoplasms/pathology , Drug Resistance, Neoplasm , Histone Demethylases/metabolism , Receptor, ErbB-2/metabolism , Signal Transduction , Transcription Factors/metabolism , Animals , Breast Neoplasms/genetics , Carcinogenesis/genetics , Carcinogenesis/pathology , Cell Line, Tumor , Drug Resistance, Neoplasm/genetics , Female , Gene Expression Regulation, Neoplastic , HEK293 Cells , Humans , Interleukin-6/metabolism , Mice, Knockout , Trans-Activators/metabolism , Up-Regulation/geneticsABSTRACT
The CD4(+) and CD8(+) T cell dichotomy is essential for effective cellular immunity. How individual T cell identity is established remains poorly understood. Here we show that the high-mobility group (HMG) transcription factors Tcf1 and Lef1 are essential for repressing CD4(+) lineage-associated genes including Cd4, Foxp3 and Rorc in CD8(+) T cells. Tcf1- and Lef1-deficient CD8(+) T cells exhibit histone hyperacetylation, which can be ascribed to intrinsic histone deacetylase (HDAC) activity in Tcf1 and Lef1. Mutation of five conserved amino acids in the Tcf1 HDAC domain diminishes HDAC activity and the ability to suppress CD4(+) lineage genes in CD8(+) T cells. These findings reveal that sequence-specific transcription factors can utilize intrinsic HDAC activity to guard cell identity by repressing lineage-inappropriate genes.
