Department of Breast, Women's Hospital of Nanjing Medical University, Nanjing Maternity and Child Health Care Hospital, Nanjing, 210004, China.
State Key Laboratory of Genetic Engineering, MOE Engineering Research Center of Gene Technology, Key Laboratory of Reproduction Regulation of NPFPC and Collaborative Innovation Center for Genetics and Development, Fudan University, Shanghai, 200438, China.
J Transl Med. 2023 Mar 26;21(1):220. doi: 10.1186/s12967-023-04031-8.
Aberrant epigenetic remodeling events contribute to progression and metastasis of breast cancer (Bca). The specific mechanims that epigenetic factors rely on to mediate tumor aggressiveness remain unclear. We aimed to elucidate the roles of epigenetic protein PHF6 in breast tumorigenesis.
Published datasets and tissue samples with PHF6 staining were used to investigate the clinical relevance of PHF6 in Bca. CCK-8, clony formation assays were used to assess cell growth capacity. Cell migration and invasion abilities were measured by Transwell assay. The gene mRNA and protein levels were measured by quantitative real-time PCR and western blot. Chromatin immunoprecipitation (ChIP)-qPCR assays were used to investigate transcriptional relationships among genes. The Co-immunoprecipitation (Co-IP) assay was used to validate interactions between proteins. The CRISPR/Cas9 editing technology was used to construct double HIF knockout (HIF-DKO) cells. The subcutaneous xenograft model and orthotopic implantation tumor model were used to asess in vivo tumor growth.
In this study, we utilized MTT assay to screen that PHF6 is required for Bca growth. PHF6 promotes Bca proliferation and migration. By analyzing The Cancer Genome Atlas breast cancer (TCGA-Bca) cohort, we found that PHF6 was significantly higher in tumor versus normal tissues. Mechanistically, PHF6 physically interacts with HIF-1α and HIF-2α to potentiate HIF-driven transcriptional events to initiate breast tumorigenesis. HIF-DKO abolished PHF6-mediated breast tumor growth, and PHF6 deficiency in turn impaired HIF transcriptional effects. Besides, hypoxia could also rely on YAP activation, but not HIF, to sustain PHF6 expressions in Bca cells. In addition, PHF6 recuits BPTF to mediate epigenetic remodeling to augment HIF transcriptional activity. Targeting PHF6 or BPTF inhibitor (AU1) is effective in mice models. Lastly, PHF6 correlated with HIF target gene expression in human breast tumors, which is an independent prognostic regulator.
Collectively, this study identified PHF6 as a prognostic epigenetic regulator for Bca, functioning as a HIF coactivator. The fundamental mechanisms underlying YAP/PHF6/HIF axis in breast tumors endowed novel epigenegtic targets for Bca treatment.
异常的表观遗传重塑事件导致乳腺癌（Bca）的进展和转移。表观遗传因子依赖于介导肿瘤侵袭性的具体机制仍不清楚。我们旨在阐明表观遗传蛋白 PHF6 在乳腺癌发生中的作用。
使用发表的数据集和 PHF6 染色的组织样本，研究 PHF6 在 Bca 中的临床相关性。CCK-8、克隆形成实验用于评估细胞生长能力。通过 Transwell 测定法测量细胞迁移和侵袭能力。通过定量实时 PCR 和 Western blot 测量基因 mRNA 和蛋白水平。染色质免疫沉淀（ChIP）-qPCR 测定用于研究基因之间的转录关系。共免疫沉淀（Co-IP）测定用于验证蛋白质之间的相互作用。使用 CRISPR/Cas9 编辑技术构建双 HIF 敲除（HIF-DKO）细胞。皮下异种移植模型和原位植入肿瘤模型用于评估体内肿瘤生长。
在这项研究中，我们利用 MTT 测定筛选出 PHF6 是 Bca 生长所必需的。PHF6 促进 Bca 的增殖和迁移。通过分析癌症基因组图谱乳腺癌（TCGA-Bca）队列，我们发现 PHF6 在肿瘤与正常组织中的表达显著升高。在机制上，PHF6 与 HIF-1α 和 HIF-2α 物理相互作用，增强 HIF 驱动的转录事件，引发乳腺癌发生。HIF-DKO 消除了 PHF6 介导的乳腺癌生长，而 PHF6 缺陷反过来又损害了 HIF 转录效应。此外，缺氧还可以依赖 YAP 激活，而不是 HIF，来维持 Bca 细胞中 PHF6 的表达。此外，PHF6 招募 BPTF 介导表观遗传重塑，增强 HIF 转录活性。针对 PHF6 或 BPTF 抑制剂（AU1）在小鼠模型中有效。最后，PHF6 与人类乳腺癌肿瘤中的 HIF 靶基因表达相关，是独立的预后调节剂。
总之，这项研究确定 PHF6 是 Bca 的一种预后表观遗传调节剂，作为 HIF 共激活剂。在乳腺癌中，YAP/PHF6/HIF 轴的基本机制为 Bca 治疗提供了新的表观遗传靶点。
