UCIBIO/REQUIMTE, Laboratório de Microbiologia, Departamento de Ciências Biológicas, Faculdade de Farmácia, Universidade do Porto, Porto, Portugal.
Laboratory of Pharmacology and Experimental Therapeutics, Institute for Biomedical Imaging and Life Sciences (IBILI), Faculty of Medicine, & CNC.IBILI Research Consortium, University of Coimbra, Coimbra, Portugal.
Cell Death Dis. 2018 Jan 18;9(2):23. doi: 10.1038/s41419-017-0154-9.
Protein kinase C (PKC) isozymes play major roles in human diseases, including cancer. Yet, the poor understanding of isozymes-specific functions and the limited availability of selective pharmacological modulators of PKC isozymes have limited the clinical translation of PKC-targeting agents. Here, we report the first small-molecule PKCδ-selective activator, the 7α-acetoxy-6β-benzoyloxy-12-O-benzoylroyleanone (Roy-Bz), which binds to the PKCδ-C1-domain. Roy-Bz potently inhibited the proliferation of colon cancer cells by inducing a PKCδ-dependent mitochondrial apoptotic pathway involving caspase-3 activation. In HCT116 colon cancer cells, Roy-Bz specifically triggered the translocation of PKCδ but not other phorbol ester responsive PKCs. Roy-Bz caused a marked inhibition in migration of HCT116 cells in a PKCδ-dependent manner. Additionally, the impairment of colonosphere growth and formation, associated with depletion of stemness markers, indicate that Roy-Bz also targets drug-resistant cancer stem cells, preventing tumor dissemination and recurrence. Notably, in xenograft mouse models, Roy-Bz showed a PKCδ-dependent antitumor effect, through anti-proliferative, pro-apoptotic, and anti-angiogenic activities. Besides, Roy-Bz was non-genotoxic, and in vivo it had no apparent toxic side effects. Collectively, our findings reveal a novel promising anticancer drug candidate. Most importantly, Roy-Bz opens the way to a new era on PKC biology and pharmacology, contributing to the potential redefinition of the structural requirements of isozyme-selective agents, and to the re-establishment of PKC isozymes as feasible therapeutic targets in human diseases.
蛋白激酶 C（PKC）同工酶在人类疾病中发挥着重要作用，包括癌症。然而，同工酶特异性功能的理解不足以及 PKC 同工酶选择性药理调节剂的有限可用性限制了 PKC 靶向药物的临床转化。在这里，我们报告了第一个小分子 PKCδ 选择性激活剂，7α-乙酰氧基-6β-苯甲酰氧基-12-O-苯甲酰基罗内酯（Roy-Bz），它与 PKCδ-C1 结构域结合。Roy-Bz 通过诱导涉及 caspase-3 激活的 PKCδ 依赖性线粒体凋亡途径，强烈抑制结肠癌细胞的增殖。在 HCT116 结肠癌细胞中，Roy-Bz 特异性触发 PKCδ 的易位，但不触发其他佛波酯反应性 PKCs 的易位。Roy-Bz 以 PKCδ 依赖性方式导致 HCT116 细胞迁移明显抑制。此外，与干细胞标志物耗竭相关的结肠球体生长和形成的损伤表明，Roy-Bz 还靶向耐药性癌症干细胞，防止肿瘤扩散和复发。值得注意的是，在异种移植小鼠模型中，Roy-Bz 通过抗增殖、促凋亡和抗血管生成作用表现出 PKCδ 依赖性的抗肿瘤作用。此外，Roy-Bz 无遗传毒性，体内无明显毒性副作用。总的来说，我们的研究结果揭示了一种有前途的新型抗癌药物候选物。最重要的是，Roy-Bz 为 PKC 生物学和药理学开辟了一个新的时代，有助于对同工酶选择性药物的结构要求进行新的定义，并重新确立 PKC 同工酶作为人类疾病可行的治疗靶点。
