Breast Tumor Center, Guangdong Provincial Key Laboratory of Malignant Tumor Epigenetics and Gene Regulation, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, 107 Yanjiang West Road, Guangzhou, 510120, P.R. China.
Department of Breast Surgery, the Second Affiliated Hospital, Guangzhou Medical University, Guangzhou, 510260, P.R. China.
Mol Cancer. 2022 Jan 3;21(1):8. doi: 10.1186/s12943-021-01476-7.
Approximate 25% HER2-positive (HER2) breast cancer (BC) patients treated with trastuzumab recurred rapidly. However, the mechanisms underlying trastuzumab resistance remained largely unclear.
Trastuzumab-resistant associated circRNAs were identified by circRNAs high-throughput screen and qRT-PCR in HER2 breast cancer tissues with different trastuzumab response. The biological roles of trastuzumab-resistant associated circRNAs were detected by cell vitality assay, colony formation assay, Edu assay, patient-derived xenograft (PDX) models and orthotopic animal models. For mechanisms research, the co-immunoprecipitation, Western blot, immunofluorescence, and pull down assays confirmed the relevant mechanisms of circRNA and binding proteins.
We identified a circRNA circCDYL2, which was overexpressed in trastuzumab-resistant patients, which conferred trastuzumab resistance in breast cancer cells in vitro and in vivo. Mechanically, circCDYL2 stabilized GRB7 by preventing its ubiquitination degradation and enhanced its interaction with FAK, which thus sustained the activities of downstream AKT and ERK1/2. Trastuzumab-resistance of HER2 BC cells with high circCDYL2 could be reversed by FAK or GRB7 inhibitor. Clinically, HER2 BC patients with high levels of circCDYL2 developed rapid recurrence and had shorter disease-free survival (DFS) and overall survival (OS) following anti-HER2 therapy compared to those with low circCDYL2.
circCDYL2-GRB7-FAK complex plays a critical role in maintaining HER2 signaling, which contributes to trastuzumab resistance and circCDYL2 is a potential biomarker for trastuzumab-resistance in HER2 BC patients.
大约 25%的曲妥珠单抗治疗的人表皮生长因子受体 2 阳性（HER2）乳腺癌（BC）患者会迅速复发。然而，曲妥珠单抗耐药的机制在很大程度上仍不清楚。
通过对不同曲妥珠单抗反应的 HER2 乳腺癌组织进行 circRNAs 高通量筛选和 qRT-PCR，鉴定出与曲妥珠单抗耐药相关的 circRNAs。通过细胞活力测定、集落形成测定、Edu 测定、患者来源的异种移植（PDX）模型和原位动物模型检测与曲妥珠单抗耐药相关的 circRNAs 的生物学作用。为了研究机制，通过共免疫沉淀、Western blot、免疫荧光和下拉测定证实了 circRNA 和结合蛋白的相关机制。
我们鉴定出一种在曲妥珠单抗耐药患者中高表达的 circRNA circCDYL2，它在体外和体内赋予乳腺癌细胞曲妥珠单抗耐药性。机制上，circCDYL2 通过阻止其泛素化降解稳定了 GRB7，并增强了其与 FAK 的相互作用，从而维持了下游 AKT 和 ERK1/2 的活性。用 FAK 或 GRB7 抑制剂可以逆转 HER2 阳性 BC 细胞中高 circCDYL2 水平的曲妥珠单抗耐药性。临床上，与低水平 circCDYL2 的患者相比，高水平 circCDYL2 的 HER2 BC 患者在接受抗 HER2 治疗后疾病无进展生存期（DFS）和总生存期（OS）迅速复发，且较短。
circCDYL2-GRB7-FAK 复合物在维持 HER2 信号中起着关键作用，导致曲妥珠单抗耐药，circCDYL2 是 HER2 BC 患者曲妥珠单抗耐药的潜在生物标志物。
