Department of Molecular-Targeting Cancer Prevention, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kawaramachi-Hirokoji, Kamigyo-ku, Kyoto, Japan.
PLoS One. 2013;8(2):e55922. doi: 10.1371/journal.pone.0055922. Epub 2013 Feb 19.
Apo2 ligand (Apo2L)/tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a promising cancer therapeutic agent. Recombinant human Apo2L/TRAIL has been under clinical trials, whereas various kinds of malignant tumors have resistance to Apo2L/TRAIL. We and others have shown that several anticancer agents and flavonoids overcome resistance to Apo2L/TRAIL by upregulating death receptor 5 (DR5) in malignant tumor cells. However, the mechanisms by which these compounds induce DR5 expression remain unknown. Here we show that the dietary flavonoid apigenin binds and inhibits adenine nucleotide translocase-2 (ANT2), resulting in enhancement of Apo2L/TRAIL-induced apoptosis by upregulation of DR5. Apigenin and genistein, which are major flavonoids, enhanced Apo2L/TRAIL-induced apoptosis in cancer cells. Apigenin induced DR5 expression, but genistein did not. Using our method identifying the direct targets of flavonoids, we compared the binding proteins of apigenin with those of genistein. We discovered that ANT2 was a target of apigenin, but not genistein. Similarly to apigenin, knockdown of ANT2 enhanced Apo2L/TRAIL-induced apoptosis by upregulating DR5 expression at the post-transcriptional level. Moreover, silencing of ANT2 attenuated the enhancement of Apo2L/TRAIL-induced apoptosis by apigenin. These results suggest that apigenin upregulates DR5 and enhances Apo2L/TRAIL-induced apoptosis by binding and inhibiting ANT2. We propose that ANT2 inhibitors may contribute to Apo2L/TRAIL therapy.
Apo2 配体（Apo2L）/肿瘤坏死因子相关凋亡诱导配体（TRAIL）是一种很有前途的癌症治疗药物。重组人 Apo2L/TRAIL 已在临床试验中进行，而各种恶性肿瘤对 Apo2L/TRAIL 具有抗性。我们和其他人已经表明，几种抗癌药物和类黄酮通过上调恶性肿瘤细胞中的死亡受体 5（DR5）来克服对 Apo2L/TRAIL 的抗性。然而，这些化合物诱导 DR5 表达的机制尚不清楚。在这里，我们表明膳食类黄酮芹菜素与腺嘌呤核苷酸转运蛋白-2（ANT2）结合并抑制其活性，从而通过上调 DR5 增强 Apo2L/TRAIL 诱导的细胞凋亡。芹菜素和染料木黄酮，这两种主要的类黄酮，增强了癌细胞中 Apo2L/TRAIL 诱导的细胞凋亡。芹菜素诱导 DR5 表达，但染料木黄酮没有。使用我们识别类黄酮直接靶标的方法，我们比较了芹菜素和染料木黄酮的结合蛋白。我们发现 ANT2 是芹菜素的靶标，但不是染料木黄酮的靶标。与芹菜素类似，敲低 ANT2 通过在转录后水平上调 DR5 表达增强 Apo2L/TRAIL 诱导的细胞凋亡。此外，沉默 ANT2 减弱了芹菜素增强的 Apo2L/TRAIL 诱导的细胞凋亡。这些结果表明，芹菜素通过结合和抑制 ANT2 上调 DR5 并增强 Apo2L/TRAIL 诱导的细胞凋亡。我们提出，ANT2 抑制剂可能有助于 Apo2L/TRAIL 治疗。
