Inhibition of AKT promotes FOXO3a-dependent apoptosis in prostate cancer.
Inhibition of AKT promotes FOXO3a-dependent apoptosis in prostate cancer.
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DOI：
10.1038/cddis.2015.403
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发表时间：
2016-02-25
影响因子：
9
通讯作者：
Damodaran C
中科院分区：
文献类型：
--
作者：
Das TP;Suman S;Alatassi H;Ankem MK;Damodaran C
生长因子诱导的蛋白激酶B(PKB)，也称为AKT，在体外转化的前列腺细胞中诱导促生存信号和抑制促凋亡信号分子的激活，包括Forkhead box O-3a(FOXO3a)转录因子和caspase。早些时候，我们报道了一种草药小分子Withaferin-A(Wa)诱导促凋亡反应-4(PAR-4)介导的去势抵抗前列腺癌(CRPC)细胞的凋亡。在本研究中，我们证明了AKT的抑制促进了FOXO3a的核穿梭，在那里它调节CRPC细胞中PAR-4的转录。FOXO3a位于PAR-4信号的上游，PAR-4信号是诱导CRPC细胞凋亡所必需的。启动子敲打研究和CH-IP分析证实了FOXO3a和PAR-4的直接相互作用；顺序删除PAR-4启动子中的FOXO3a结合位点未能诱导PAR-4激活。为了证实这些观察结果，我们在CRPC细胞中过表达AKT或沉默FOXO3a激活。这两种方法都抑制了PAR-4的功能，并显著抑制了细胞凋亡。在AKT过表达的CRPC细胞来源的异种移植瘤中，FOXO3a和PAR-4的表达下调，导致肿瘤的侵袭性生长。口服Wa可恢复FOXO3a介导的PAR-4功能，抑制肿瘤生长。最后，AKT表达的核定位与人前列腺组织阵列中的PAR-4胞浆定位呈负相关。我们的研究表明，PAR-4是FOXO3a的关键转录靶点之一，而PAR-4的激活是诱导CRPC细胞凋亡所必需的。FOXO3a的激活似乎是治疗CRPC的一个有吸引力的靶点，Wa等分子可以进一步探索用于治疗CRPC的分子。
Growth factor-induced activation of protein kinase-B (PKB), also known as AKT, induces pro-survival signaling and inhibits activation of pro-apoptotic signaling molecules including the Forkhead box O-3a (FOXO3a) transcription factor and caspase in transformed prostate cells in vitro. Earlier we reported that Withaferin-A (WA), a small herbal molecule, induces pro-apoptotic response-4 (Par-4) mediated apoptosis in castration-resistant prostate cancer (CRPC) cells. In the present study, we demonstrate that inhibition of AKT facilitates nuclear shuttling of FOXO3a where it regulates Par-4 transcription in CRPC cells. FOXO3a is upstream of Par-4 signaling, which is required for induction of apoptosis in CRPC cells. Promoter bashing studies and Ch-IP analysis confirm a direct interaction of FOXO3a and Par-4; a sequential deletion of FOXO3a-binding sites in the Par-4 promoter fails to induce Par-4 activation. To confirm these observations, we either overexpressed AKT or silenced FOXO3a activation in CRPC cells. Both methods inhibit Par-4 function and apoptosis is significantly compromised. In xenograft tumors derived from AKT-overexpressed CRPC cells, FOXO3a and Par-4 expression is downregulated, leading to aggressive tumor growth. Oral administration of WA to mice with xenograft tumors restores FOXO3a-mediated Par-4 functions and results in inhibited tumor growth. Finally, an inverse correlation of nuclear localization of AKT expression corresponds to cytoplasmic Par-4 localization in human prostate tissue array. Our studies suggest that Par-4 is one of the key transcriptional targets of FOXO3a, and Par-4 activation is required for induction of apoptosis in CRPC cells. Activation of FOXO3a appears to be an attractive target for the treatment of CRPC and molecules such as WA can be explored further for the treatment of CRPC.