Steely Andrea M, Willoughby Jamin A, Sundar Shyam N, Aivaliotis Vasiliki I, Firestone Gary L
Department of Molecular and Cell Biology, Cancer Research Laboratory, University of California at Berkeley, Berkeley, California, USA.
Anticancer Drugs. 2017 Oct;28(9):1018-1031. doi: 10.1097/CAD.0000000000000547.
Androgen receptor (AR) expression and activity is highly linked to the development and progression of prostate cancer and is a target of therapeutic strategies for this disease. We investigated whether the antimalarial drug artemisinin, which is a sesquiterpene lactone isolated from the sweet wormwood plant Artemisia annua, could alter AR expression and responsiveness in cultured human prostate cancer cell lines. Artemisinin treatment induced the 26S proteasome-mediated degradation of the receptor protein, without altering AR transcript levels, in androgen-responsive LNCaP prostate cancer cells or PC-3 prostate cancer cells expressing exogenous wild-type AR. Furthermore, artemisinin stimulated AR ubiquitination and AR receptor interactions with the E3 ubiquitin ligase MDM2 in LNCaP cells. The artemisinin-induced loss of AR protein prevented androgen-responsive cell proliferation and ablated total AR transcriptional activity. The serine/threonine protein kinase AKT-1 was shown to be highly associated with artemisinin-induced proteasome-mediated degradation of AR protein. Artemisinin treatment activated AKT-1 enzymatic activity, enhanced receptor association with AKT-1, and induced AR serine phosphorylation. Treatment of LNCaP cells with the PI3-kinase inhibitor LY294002, which inhibits the PI3-kinase-dependent activation of AKT-1, prevented the artemisinin-induced AR degradation. Furthermore, in transfected receptor-negative PC-3 cells, artemisinin failed to stimulate the degradation of an altered receptor protein (S215A/S792A) with mutations in its two consensus AKT-1 serine phosphorylation sites. Taken together, our results indicate that artemisinin induces the degradation of AR protein and disrupts androgen responsiveness of human prostate cancer cells, suggesting that this natural compound represents a new potential therapeutic molecule that selectively targets AR levels.
雄激素受体（AR）的表达和活性与前列腺癌的发生和发展密切相关，是该疾病治疗策略的靶点。我们研究了从青蒿植物黄花蒿中分离出的倍半萜内酯抗疟药物青蒿素是否能改变培养的人前列腺癌细胞系中AR的表达和反应性。在雄激素反应性LNCaP前列腺癌细胞或表达外源性野生型AR的PC-3前列腺癌细胞中，青蒿素处理诱导了26S蛋白酶体介导的受体蛋白降解，而不改变AR转录水平。此外，青蒿素刺激了LNCaP细胞中AR的泛素化以及AR受体与E3泛素连接酶MDM2的相互作用。青蒿素诱导的AR蛋白缺失阻止了雄激素反应性细胞增殖，并消除了总AR转录活性。丝氨酸/苏氨酸蛋白激酶AKT-1被证明与青蒿素诱导的蛋白酶体介导的AR蛋白降解高度相关。青蒿素处理激活了AKT-1酶活性，增强了受体与AKT-1的结合，并诱导了AR丝氨酸磷酸化。用PI3激酶抑制剂LY294002处理LNCaP细胞，该抑制剂抑制PI3激酶依赖性的AKT-1激活，阻止了青蒿素诱导的AR降解。此外，在转染的受体阴性PC-3细胞中，青蒿素未能刺激在其两个共有AKT-1丝氨酸磷酸化位点发生突变的改变受体蛋白（S215A/S792A）的降解。综上所述，我们的结果表明青蒿素诱导AR蛋白降解并破坏人前列腺癌细胞的雄激素反应性，表明这种天然化合物代表了一种选择性靶向AR水平的新的潜在治疗分子。
