STAT3/miR-221-3p/Fascin-1调控三阴性乳腺癌EGFR TKI耐药的作用机制

Although epidermal growth factor receptor 1 (EGFR) is overexpressed in triple-negative breast cancer (TNBC), the clinical efficacy of gefitinib and other EGFR tyrosine kinase inhibitors (TKIs) used in the treatment of TNBC is weak and mechanism of that is unknown. We found that cytoskeletal molecule Fascin-1 (FSCN1) was associated with gefitinib resistance in TNBC. FSCN1 inhibition can rescue cell drug-resistant. Also, inhibition of STAT3 activity reversed drug resistance, and subsequently decreased expression of FSCN1, and increased expression of miR-221-3p, which may target FSCN1. Therefore, we hypothesize that STAT3 may regulate EGFR TKI sensitivity mediated by the level of miR-221-3p-FSCN1 in TNBC cells. STAT3 inhibitor combined with TKI is expected to be a new method in the treatment of TNBC. We explore the molecular mechanism of EGFR TKI resistance in TNBC cells and to the effect of TKI combined with FSCN1 or STAT3 multi-target intervention on TNBC. Such work might be enlightening to improve clinical EGFR TKI therapy in patients with TNBC, seek new alternative or combination targeted therapeutic molecules, and provide new ideas and theoretical basis.

尽管表皮生长因子受体1（EGFR）在三阴性乳腺癌（TNBC）中高表达，但吉非替尼等EGFR酪氨酸激酶抑制剂（TKI）治疗TNBC的临床疗效一般，其机制不详。我们发现细胞骨架分子Fascin-1（FSCN1）与TNBC的吉非替尼耐药相关，抑制FSCN1后耐药细胞恢复敏感性；抑制STAT3活性亦可逆转耐药，下调FSCN1表达，而可能靶向抑制FSCN1的miR-221-3p却表达上调。因此，我们推测STAT3可能通过调控miR-221-3p-FSCN1表达来调节TNBC细胞对EGFR TKI敏感性。STAT3抑制剂联合TKI有望成为治疗TNBC的新方法。本项目拟解析TNBC细胞EGFR TKI耐药的分子机制，并探讨TKI联合FSCN1或STAT3多靶点干预对TNBC的疗效，为解决TNBC患者EGFR TKI治疗有效率低下难题，寻求新的替代性或联合性靶向治疗分子提供新的思路和理论基础。

尽管表皮生长因子受体1（EGFR）在三阴性乳腺癌（TNBC）中高表达，但吉非替尼等EGFR酪氨酸激酶抑制剂（TKI）治疗TNBC的临床疗效一般，其机制不详。本项目拟证实Fascin-1（FSCN1）在TNBC细胞对EGFR TKI原发耐药中的作用，并进一步阐明FSCN1的表达调控机制，揭示信号转导及转录激活因子3（STAT3）-miR-221-3p-FSCN1轴在调控TNBC细胞对EGFR TKI敏感性中的作用，同时明确EGFR TKI联合FSCN1或STAT3多靶点干预对TNBC的潜在治疗效果。结果显示TNBC细胞MDA-MB-231和MDA-MB-468对Gefitinib均原发耐药，且TNBC细胞和组织中EGFR蛋白表达均显著高于non-TNBC。Gefitinib作用MDA-MB-231和MDA-MB-468细胞后，ERK1/2磷酸化程度下降，FSCN1表达上调。抑制FSCN1表达可显著提高MDA-MB-231和MDA-MB-468细胞对Gefitinib的敏感性。Gefitinib作用MDA-MB-231和MDA-MB-468细胞后miR-221-3p表达下调。过表达外源性miR-221-3p可显著提高MDA-MB-231和MDA-MB-468细胞对Gefitinib的敏感性，并下调FSCN1表达；而敲减miR-221-3p引起FSCN1表达升高；荧光素酶报告实验证实FSCN1为miR-221-3p的靶基因。Gefitinib作用MDA-MB-231细胞后STAT3磷酸化程度上升。应用Stattic抑制STAT3活性可显著增强Gefitinib对MDA-MB-231细胞生长、迁移及侵袭能力的抑制，同时上调miR-221-3p表达并下调FSCN1表达。乳腺癌组织中STAT3和FSCN1表达呈显著正相关，它们同时高表达的患者预后明显更差。本项目首次发现FSCN1表达升高与TNBC对EGFR TKI原发耐药相关，并进一步发现STAT3可能通过miR-221-3p来调控FSCN1表达，从而影响TNBC细胞对EGFR TKI的敏感性。本项目基本阐明了FSCN1在TNBC对EGFR TKI耐药中的作用及相关调控机制。研究结果提示EGFR TKI联合FSCN1或STAT3多靶点作用对TNBC具有显著的抑制作用，从而为今后多靶点联合治疗TNBC提供了新的理论基础。