Data_Sheet_1_Carnosol, a Natural Polyphenol, Inhibits Migration, Metastasis, and Tumor Growth of Breast Cancer via a ROS-Dependent Proteasome Degradation of STAT3.PDF

We have previously demonstrated that carnosol, a naturally occurring diterpene, inhibited in vitro cell viability and colony growth, as well as induced cell cycle arrest, autophagy and apoptosis in human triple negative breast cancer (TNBC) cells. In the present study, we evaluated the ability of carnosol to inhibit tumor growth and metastasis in vivo. We found that non-cytotoxic concentrations of carnosol inhibited the migration and invasion of MDA-MB-231 cells in wound healing and matrigel invasion assays. Furthermore, gelatin zymography, ELISA, and RT-PCR assays revealed that carnosol inhibited the activity and downregulation the expression of MMP-9. Mechanistically, we demonstrated that carnosol suppressed the activation of STAT3 signaling pathway through a ROS-dependent targeting of STAT3 to proteasome-degradation in breast cancer cells (MDA-MB-231, Hs578T, MCF-7, and T47D). We show that blockade of proteasome activity, by MG-132 and bortezomib, or ROS accumulation, by N-acetylcysteine (NAC), restored the level of STAT3 protein. In addition, using chick embryo tumor growth assay, we showed that carnosol significantly and markedly suppressed tumor growth and metastasis of breast cancer xenografts. To the best of our knowledge, this is the first report which shows that carnosol specifically targets signal transducer and activator of transcription 3 (STAT3) for proteasome degradation in breast cancer. Our study further provide evidence that carnosol may represent a promising therapeutic candidate that canmodulate breast cancer growth and metastasis.

先前研究表明，天然存在的二萜类化合物卡诺索尔，可在体外抑制细胞活力和集落生长，并诱导人三阴性乳腺癌（TNBC）细胞周期阻滞、自噬和凋亡。在本研究中，我们评估了卡诺索尔在体内抑制肿瘤生长和转移的能力。我们发现，非细胞毒性浓度的卡诺索尔在伤口愈合和Matrigel侵袭实验中抑制了MDA-MB-231细胞的迁移和侵袭。此外，凝胶酶谱、ELISA和RT-PCR实验显示，卡诺索尔抑制了MMP-9的活性和下调其表达。机制研究表明，卡诺索尔通过依赖活性氧（ROS）将STAT3靶向至蛋白酶体降解，从而抑制了STAT3信号通路的激活。在乳腺癌细胞（MDA-MB-231、Hs578T、MCF-7和T47D）中，我们展示了蛋白酶体活性阻断剂MG-132和硼替佐米，或ROS积累抑制剂N-乙酰半胱氨酸（NAC）均能恢复STAT3蛋白水平。此外，通过鸡胚肿瘤生长实验，我们证明了卡诺索尔显著抑制了乳腺癌异种移植肿瘤的生长和转移。据我们所知，这是首次报道卡诺索尔在乳腺癌中特异性靶向信号转导和转录激活因子3（STAT3）进行蛋白酶体降解的研究。我们的研究进一步提供了证据，表明卡诺索尔可能成为一种具有潜力的治疗候选药物，能够调节乳腺癌的生长和转移。