Objective: Breast cancer stem cells (BCSC) have been suggested to have clinical implications for cancer therapeutics because of their proposed role in chemo-resistance. The aim of this study was to investigate effects of BCSC on endocrine therapy response by regulating PI3K/Akt/mTOR signaling pathway. Methods: We evaluated the susceptibility of BCSC to NVP-BKM120 (BKM120), a new generation of PI3K-specific inhibitor, when used individually or in combination with letrozole in vivo. For this, a stem-like cell population (SC) was enriched from breast cancer cell line MCF-7 after mammosphere cultures. We have constructed high aromatase expression BCSC (BCSC-CYP19) and non-stem cells (MCF-7-CYP19) subcloning. We demonstrate BKM120 inhibits growth, generation of drug-resistant derivatives and SC formation in BCSC-CYP19 and MCF-7-CYP19. Result: BKM120 could inhibit BCSC-CYP19 growth by dose-dependence, reduce migration and colony formation of BCSC-CYP19, and also significantly reduced expression of PI3K, Akt1 and S6. Combined BKM120 and letrozolecaninhibit BCSC-CYP19 growth and proliferation, make BCSC-CYP19 stayed in G0-G1 phase increasing significantly to induce early apoptosis, and down-regulate expression of PI3K, Akt1 and S6. Conclusion: PI3K/Akt/mTOR pathway effects on letrozole resistance by regulating BCBSs characteristics. Combination of PI3K inhibitor BKM120 and letrozole could reduce letrozole resistance.
目的： 通过调节PI3K/Akt/mTOR信号通路中PI3K对乳腺癌干细胞（BCSC）的作用对内分泌治疗敏感性的影响。 方法： 采用无血清培养液悬浮培养球囊细胞的方法富集乳腺癌细胞系MCF-7中的BCSC，使用流式仪分选出ESA(+)CD44(+)CD24(-/low)亚群，并对其进行克隆培养。构建高表达芳香化酶的BCSC（BCSC-CYP19）和非干细胞（MCF-7-CYP19）亚克隆。通过MTT检测、划痕实验、流式细胞术、软琼脂克隆实验评价BCSC干性特征，利用Western印迹检测PI3K/mTOR通路中Akt1、PI3K、S6的蛋白表达水平，从而比较单用PI3K靶向抑制剂NVP-BKM120（BKM120）或联合来曲唑对BCSC-CYP19和MCF-7-CYP19的作用影响。 结果： BKM120通过剂量依赖性抑制BCSC-CYP19的生长，减少BCSC-CYP19的移动和集落形成，并显著降低PI3K、Akt1和S6的表达。BKM120联合来曲唑可抑制BCSC-CYP19的生长和增殖，使BCSC-CYP19在G0~G1期显著增加，诱导早期凋亡，下调PI3K、Akt1和S6的表达。 结论： PI3K/Akt/mTOR信号通路通过调节BCSC特性以影响来曲唑的耐药。PI3K抑制剂BKM120和来曲唑联合应用可抑制来曲唑耐药。.
Keywords: Breast neoplasms; Letrozole; NVP-BKM120; PI3K/Akt/mTOR; Stem cells.