Department of Pathology, College of Medicine, Hanyang University, Seoul, Republic of Korea; Research Institute of Pharmaceutical Sciences, College of Pharmacy, Seoul National University, Seoul, Republic of Korea; Institute for Bioengineering and Biopharmaceutical Research (IBBR), Hanyang University, Seoul, Republic of Korea.
J Natl Cancer Inst. 2018 Apr 1;110(4). doi: 10.1093/jnci/djx207.
Despite the benefit of endocrine therapy, acquired resistance during or after treatment still remains a major challenge in estrogen receptor (ER)-positive breast cancer. We investigated the potential role of histone demethylase retinoblastoma-binding protein 2 (RBP2) in endocrine therapy resistance of breast cancer.
Survival of breast cancer patients according to RBP2 expression was analyzed in three different breast cancer cohorts including METABRIC (n = 1980) and KM plotter (n = 1764). RBP2-mediated tamoxifen resistance was confirmed by invitro sulforhodamine B (SRB) colorimetric, colony-forming assays, and invivo xenograft models (n = 8 per group). RNA-seq analysis and receptor tyrosine kinase assay were performed to identify the tamoxifen resistance mechanism by RBP2. All statistical tests were two-sided.
RBP2 was associated with poor prognosis to tamoxifen therapy in ER-positive breast cancer (P = .04 in HYU cohort, P = .02 in KM plotter, P = .007 in METABRIC, log-rank test). Furthermore, RBP2 expression was elevated in patients with tamoxifen-resistant breast cancer (P = .04, chi-square test). Knockdown of RBP2 conferred tamoxifen sensitivity, whereas overexpression of RBP2 induced tamoxifen resistance invitro and invivo (MCF7 xenograft: tamoxifen-treated control, mean [SD] tumor volume = 70.8 [27.9] mm3, vs tamoxifen-treated RBP2, mean [SD] tumor volume = 387.9 [85.1] mm3, P < .001). Mechanistically, RBP2 cooperated with ER co-activators and corepressors and regulated several tamoxifen resistance-associated genes, including NRIP1, CCND1, and IGFBP4 and IGFBP5. Furthermore, epigenetic silencing of IGFBP4/5 by RBP2-ER-NRIP1-HDAC1 complex led to insulin-like growth factor-1 receptor (IGF1R) activation. RBP2 also increased IGF1R-ErbB crosstalk and subsequent PI3K-AKT activation via demethylase activity-independent ErbB protein stabilization. Combinational treatment with tamoxifen and PI3K inhibitor could overcome RBP2-mediated tamoxifen resistance (RBP2-overexpressing cells: % cell viability [SD], tamoxifen = 89.0 [3.8]%, vs tamoxifen with BKM120 = 41.3 [5.6]%, P < .001).
RBP2 activates ER-IGF1R-ErbB signaling cascade in multiple ways to induce tamoxifen resistance, suggesting that RBP2 is a potential therapeutic target for ER-driven cancer.
尽管内分泌治疗有获益，但在治疗期间或之后获得的耐药仍然是雌激素受体（ER）阳性乳腺癌的主要挑战。我们研究了组蛋白去甲基酶视黄醇结合蛋白 2（RBP2）在乳腺癌内分泌治疗耐药中的潜在作用。
在包括 METABRIC（n=1980）和 KM plotter（n=1764）在内的三个不同的乳腺癌队列中，根据 RBP2 表达分析乳腺癌患者的生存情况。通过体外磺酰罗丹明 B（SRB）比色、集落形成测定和体内异种移植模型（每组 n=8）证实了 RBP2 介导的他莫昔芬耐药。进行 RNA-seq 分析和受体酪氨酸激酶测定，以确定 RBP2 介导的他莫昔芬耐药机制。所有统计检验均为双侧检验。
在 ER 阳性乳腺癌中，RBP2 与他莫昔芬治疗的不良预后相关（HYU 队列中 P=0.04，KM plotter 中 P=0.02，METABRIC 中 P=0.007，对数秩检验）。此外，在他莫昔芬耐药性乳腺癌患者中 RBP2 的表达水平升高（P=0.04，卡方检验）。RBP2 的敲低赋予了他莫昔芬敏感性，而 RBP2 的过表达在体外和体内诱导了他莫昔芬耐药（MCF7 异种移植：他莫昔芬治疗对照组，平均[标准差]肿瘤体积=70.8[27.9]mm3，vs 他莫昔芬治疗 RBP2，平均[标准差]肿瘤体积=387.9[85.1]mm3，P<.001）。在机制上，RBP2 与 ER 共激活子和共抑制子合作，并调节了几种他莫昔芬耐药相关基因，包括 NRIP1、CCND1 和 IGFBP4 和 IGFBP5。此外，RBP2-ER-NRIP1-HDAC1 复合物通过对 IGFBP4/5 的表观遗传沉默导致胰岛素样生长因子-1 受体（IGF1R）激活。RBP2 还通过去甲基酶活性非依赖性 ErbB 蛋白稳定增加 IGF1R-ErbB 串扰和随后的 PI3K-AKT 激活。联合使用他莫昔芬和 PI3K 抑制剂可以克服 RBP2 介导的他莫昔芬耐药（RBP2 过表达细胞：%细胞活力[标准差]，他莫昔芬=89.0[3.8]%，vs 他莫昔芬+BKM120=41.3[5.6]%，P<.001）。
RBP2 通过多种方式激活 ER-IGF1R-ErbB 信号级联，诱导他莫昔芬耐药，表明 RBP2 是一种潜在的 ER 驱动型癌症治疗靶点。
