Affiliated Cancer Hospital & Institute of Guangzhou Medical University; Guangzhou Municipal and Guangdong Provincial Key Laboratory of Protein Modification and Degradation; The State Key Laboratory of Respiratory; Guangzhou Key Laboratory of "Translational Medicine on Malignant Tumor Treatment", Hengzhigang Road 78#, Guangzhou 510095, Guangdong, China.
Guangzhou Municipal and Guangdong Provincial Key Laboratory of Protein Modification and Degradation, School of Basic Medical Sciences, Guangzhou Medical University, Guangzhou, Guangdong, China.
Theranostics. 2020 Mar 4;10(10):4290-4307. doi: 10.7150/thno.41008. eCollection 2020.
: Chemoresistance is a significant obstacle to the effective treatment of breast cancer (BC), resulting in more aggressive behavior and worse clinical outcome. The molecular mechanisms underlying breast cancer chemoresistance remain unclear. Our microarray analysis had identified the overexpression of a small molecular glycoprotein serglycin (SRGN) in multidrug-resistant BC cells. Here, we aimed to investigate the role of SRGN in chemoresistance of breast cancer and elucidate the underlying mechanisms. : SRNG overexpression was identified using microarray analysis and its clinical relevance was analyzed. To investigate the role of SRGN, we performed various and studies, as well as characterization of serum and tissue samples from BC patients. Chemosensitivity measurement, gene expression interference, immunofluorescence staining, mammosphere assay, flow cytometry analysis, luciferase reporter assay, ChIP-qPCR, coimmunoprecipitation, and immunohistochemistry were performed to explore the potential functions and mechanisms of SRGN. : We confirmed overexpression of SRGN in chemoresistant BC cells and in serum and tissue samples from BC patients with poor response to chemotherapy. SRGN specifically predicted poor prognosis in BC patients receiving chemotherapy. Mechanistically, SRGN promoted chemoresistance both and by cross-talking with the transcriptional coactivator YES-associated protein (YAP) to maintain stemness in BC cells. Ectopic YAP expression restored the effects of knockdown. Inversely, YAP knockdown rescued the effects of overexpression. The secreted SRGN triggered ITGA5/FAK/CREB signaling to enhance transcription. Reciprocally, YAP promoted transcription in a TEAD1-dependent manner to form a feed-forward circuit. Moreover, the YAP/RUNX1 complex promoted transcription to induce chemoresistance and stemness in BC cells. Importantly, the SRGN levels were positively correlated with the YAP and HDAC2 levels in chemoresistant BC tissues. YAP and HDAC2 acted downstream of SRNG and correlated with poor outcomes of BC patients receiving chemotherapy. : Our findings clarify the roles and mechanisms of SRGN in mediating chemoresistance in breast cancer and suggest its use a potential biomarker for chemotherapeutic response. We believe that novel therapeutic strategies for breast cancer can be designed by targeting the signaling mediated by the crosstalk between SRGN and YAP.
化学耐药性是乳腺癌（BC）有效治疗的重大障碍，导致更具侵袭性的行为和更差的临床结局。乳腺癌化学耐药性的分子机制尚不清楚。我们的微阵列分析已经确定了多药耐药性 BC 细胞中小分子糖蛋白神经节苷脂（SRGN）的过表达。在这里，我们旨在研究 SRGN 在乳腺癌耐药中的作用，并阐明其潜在机制。
通过微阵列分析鉴定 SRNG 的过表达，并分析其临床相关性。为了研究 SRGN 的作用，我们进行了各种体外和体内研究，以及对来自 BC 患者的血清和组织样本进行了特征描述。进行了化疗敏感性测量、基因表达干扰、免疫荧光染色、乳腺球体测定、流式细胞术分析、荧光素酶报告基因测定、ChIP-qPCR、共免疫沉淀和免疫组织化学，以探索 SRGN 的潜在功能和机制。
我们证实了化学耐药性 BC 细胞以及对化疗反应不佳的 BC 患者的血清和组织样本中 SRGN 的过表达。SRGN 特异性预测了接受化疗的 BC 患者的不良预后。在机制上，SRGN 通过与转录共激活因子 YES 相关蛋白（YAP）相互作用，在 BC 细胞中维持干性，从而促进了化疗耐药性。外源性 YAP 表达恢复了 siRNA 敲低的作用。相反，YAP 敲低挽救了过表达的效果。分泌的 SRGN 触发 ITGA5/FAK/CREB 信号以增强转录。反过来，YAP 以 TEAD1 依赖性方式促进转录，形成正反馈回路。此外，YAP/RUNX1 复合物促进转录，诱导 BC 细胞的化疗耐药性和干性。重要的是，SRGN 水平与化学耐药性 BC 组织中的 YAP 和 HDAC2 水平呈正相关。YAP 和 HDAC2 位于 SRGN 下游，与接受化疗的 BC 患者的不良预后相关。
我们的研究结果阐明了 SRGN 在介导乳腺癌化疗耐药中的作用和机制，并表明其可用作化疗反应的潜在生物标志物。我们相信，可以通过靶向 SRGN 和 YAP 之间的串扰介导的信号来设计针对乳腺癌的新型治疗策略。
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