Department of Pharmaceutical Sciences, Daniel K. Inouye College of Pharmacy, University of Hawaii at Hilo, 200 W. Kawili St., Hilo, HI 96720, United States.
Department of Pharmaceutical Sciences, Daniel K. Inouye College of Pharmacy, University of Hawaii at Hilo, 200 W. Kawili St., Hilo, HI 96720, United States; University of Hawaii Cancer Center, 701 Ilalo Street, Honolulu, HI 96813, United States.
Biochem Pharmacol. 2014 Feb 1;87(3):445-55. doi: 10.1016/j.bcp.2013.11.014. Epub 2013 Nov 28.
Heat shock protein 90 (Hsp90) has an important role in many cancers. Biochemical inhibitors of Hsp90 are in advanced clinical development for the treatment of solid and hematological malignancies. At the cellular level, their efficacy is diminished by the fact that Hsp90 inhibition causes activation of heat shock factor 1 (HSF1). We report a mechanism by which HSF1 activation diminishes the effect of Hsp90 inhibitors geldanamycin and 17-allylaminogeldanamycin (17-AAG, tanespimycin). Silencing HSF1 with siRNA or inhibiting HSF1 activity with KRIBB11 lowers the threshold for apoptosis in geldanamycin and 17-AAG-treated cancer cells. Autophagy also mitigates the actions of Hsp90 inhibitors. Blocking autophagy with 3-methyladenine (3-MA), bafilomycin A1, or beclin 1 siRNA also lower the threshold for apoptosis. Exploring a potential relationship between HSF1 and autophagy, we monitored autophagosome formation and autophagic flux in control and HSF1-silenced cells. Results show HSF1 is required for autophagy in Hsp90 inhibitor-treated cells. The reduced autophagy observed in HSF1-silenced cells correlates with enhanced cell death. To investigate how HSF1 promotes autophagy, we monitored the expression of genes involved in the autophagic cascade. These data show that sequestosome 1 (p62/SQSTM1), a protein involved in the delivery of autophagic substrates and nucleation of autophagosomes, is an HSF1-regulated gene. Gene silencing was used to evaluate the significance of p62/SQSTM1 in Hsp90 inhibitor resistance. Cells where p62/SQSTM1 was silenced showed a dramatic increase in sensitivity to Hsp90 inhibitors. Results highlight the importance of HSF1 and HSF1-dependent p62/SQSTM1 expression in resistance Hsp90 inhibitors, underscoring the potential of targeting HSF1 to improve the efficacy of Hsp90 inhibitors in cancer.
热休克蛋白 90(Hsp90)在许多癌症中具有重要作用。Hsp90 的生化抑制剂正在进行高级临床开发,用于治疗实体瘤和血液恶性肿瘤。在细胞水平上,由于 Hsp90 抑制会导致热休克因子 1(HSF1)的激活,因此它们的功效降低。我们报告了一种机制,通过该机制,HSF1 的激活会降低 Hsp90 抑制剂格尔德霉素和 17-烯丙基氨基格尔德霉素(17-AAG,坦西普霉素)的作用。用 siRNA 沉默 HSF1 或用 KRIBB11 抑制 HSF1 活性可降低格尔德霉素和 17-AAG 处理的癌细胞中细胞凋亡的阈值。自噬也减轻了 Hsp90 抑制剂的作用。用 3-甲基腺嘌呤(3-MA)、巴弗洛霉素 A1 或 beclin 1 siRNA 阻断自噬也会降低细胞凋亡的阈值。为了探索 HSF1 和自噬之间的潜在关系,我们在对照和 HSF1 沉默的细胞中监测自噬体的形成和自噬流。结果表明,在 Hsp90 抑制剂处理的细胞中,HSF1 是自噬所必需的。在 HSF1 沉默的细胞中观察到的自噬减少与细胞死亡增强相关。为了研究 HSF1 如何促进自噬,我们监测了参与自噬级联反应的基因的表达。这些数据表明,自噬体形成过程中的底物输送和自噬体成核涉及的蛋白 sequestosome 1(p62/SQSTM1)是一种 HSF1 调节基因。使用基因沉默来评估 p62/SQSTM1 在 Hsp90 抑制剂抗性中的重要性。沉默 p62/SQSTM1 的细胞对 Hsp90 抑制剂的敏感性显著增加。结果强调了 HSF1 和 HSF1 依赖性 p62/SQSTM1 表达在 Hsp90 抑制剂抗性中的重要性,突显了靶向 HSF1 以提高 Hsp90 抑制剂在癌症中的疗效的潜力。