Furfaro A L, Piras S, Domenicotti C, Fenoglio D, De Luigi A, Salmona M, Moretta L, Marinari U M, Pronzato M A, Traverso N, Nitti M
Giannina Gaslini Institute, Via Gerolamo Gaslini 5, 16147, Genova, Italy.
Department of Experimental Medicine, University of Genoa, Via L.B. Alberti 2, 16132, Genova, Italy.
PLoS One. 2016 Mar 29;11(3):e0152465. doi: 10.1371/journal.pone.0152465. eCollection 2016.
The activation of Nrf2 has been demonstrated to play a crucial role in cancer cell resistance to different anticancer therapies. The inhibition of proteasome activity has been proposed as a chemosensitizing therapy but the activation of Nrf2 could reduce its efficacy. Using the highly chemoresistant neuroblastoma cells HTLA-230, here we show that the strong reduction in proteasome activity, obtained by using low concentration of bortezomib (BTZ, 2.5 nM), fails in reducing cell viability. BTZ treatment favours the binding of Nrf2 to the ARE sequences in the promoter regions of target genes such as heme oxygenase 1 (HO-1), the modulatory subunit of γ-glutamylcysteine ligase (GCLM) and the transporter for cysteine (x-CT), enabling their transcription. GSH level is also increased after BTZ treatment. The up-regulation of Nrf2 target genes is responsible for cell resistance since HO-1 silencing and GSH depletion synergistically decrease BTZ-treated cell viability. Moreover, cell exposure to all-trans-Retinoic acid (ATRA, 3 μM) reduces the binding of Nrf2 to the ARE sequences, decreases HO-1 induction and lowers GSH level increasing the efficacy of bortezomib. These data suggest the role of Nrf2, HO-1 and GSH as molecular targets to improve the efficacy of low doses of bortezomib in the treatment of malignant neuroblastoma.
Nrf2的激活已被证明在癌细胞对不同抗癌疗法的抗性中起关键作用。蛋白酶体活性的抑制已被提议作为一种化学增敏疗法，但Nrf2的激活可能会降低其疗效。利用高度化学抗性的神经母细胞瘤细胞HTLA-230，我们在此表明，使用低浓度硼替佐米（BTZ，2.5 nM）导致蛋白酶体活性大幅降低，但未能降低细胞活力。BTZ处理有利于Nrf2与靶基因（如血红素加氧酶1（HO-1）、γ-谷氨酰半胱氨酸连接酶调节亚基（GCLM）和半胱氨酸转运体（x-CT））启动子区域的ARE序列结合，从而使其转录。BTZ处理后谷胱甘肽（GSH）水平也会升高。Nrf2靶基因的上调导致细胞抗性，因为HO-1沉默和GSH耗竭协同降低BTZ处理后的细胞活力。此外，细胞暴露于全反式维甲酸（ATRA，3 μM）可减少Nrf2与ARE序列的结合，降低HO-1的诱导并降低GSH水平，从而提高硼替佐米的疗效。这些数据表明Nrf2、HO-1和GSH作为分子靶点在提高低剂量硼替佐米治疗恶性神经母细胞瘤疗效方面的作用。
