——破解“不可成药”魔咒:靶向MYC的肿瘤治疗药物研发全景
癌症是全球重大公共卫生挑战,而基因表达失调是其发生发展的核心。在众多癌基因中,骨髓细胞瘤病毒癌基因同源物(MYC)堪称“癌王”,其表达异常与近70%的人类恶性肿瘤相关,是驱动肿瘤生长、代谢重编程和免疫逃逸的关键引擎。然而,MYC蛋白长期以来因其缺乏明确的药物结合口袋,被贴上了“不可成药”的标签。近日,发表于《药学进展》的一篇综述系统梳理了靶向MYC的各类策略,从直接干扰其蛋白互作到表观遗传调控,为我们全景展示了破解这一难题的最新研究图景。一、MYC:癌症的“中央指挥官”及其“不可成药”困境1.1 结构与功能:一个全能转录因子
MYC家族包括C-MYC、N-MYC和L-MYC,均属于碱性-螺旋-环-螺旋-亮氨酸拉链(b-HLH-LZ)转录因子。正常情况下,MYC需要与MYC相关因子X(MAX)形成异二聚体,才能结合DNA上的E-box序列(CANNTG),从而调控约15%的基因组转录,深刻影响细胞生长、分裂、分化、代谢和凋亡等关键生命过程。1.2 肿瘤中的MYC:从驱动者到“扩音器”
在肿瘤中,MYC的异常激活(常通过基因扩增、染色体易位等机制)使其成为恶性转化的强大驱动因素。过表达的MYC不仅增强对高亲和力启动子的结合,还会“入侵”增强子等低亲和力位点,导致全局性转录扩增,如同一个失控的“基因扩音器”,推动肿瘤发生发展。此外,MYC还参与肿瘤血管生成、促进上皮-间质转化(EMT),并关键性地塑造免疫抑制性肿瘤微环境,帮助癌细胞逃避免疫监视。二、靶向MYC的多元策略:从正面强攻到迂回包抄2.1 干扰MYC-MAX-DNA相互作用
既然MYC功能的行使依赖其与MAX的异二聚化以及与DNA的结合,那么破坏这些蛋白相互作用便成为最直接的策略。目前主要有三类路径:抑制MYC-MAX异二聚体(如小分子MYCMI-6/7、MYci361/975,以及多肽药物omomyc,后者已进入I/II期临床试验);稳定MAX-MAX同二聚体以竞争性阻断MYC-MAX形成(如KI-MS2-008);直接干扰MYC-MAX与DNA的结合(如雷公藤红素、VPC-70619、KSI-3716)。2.2 调控MYC的表达水平
如果不能直接抑制MYC蛋白,那么“釜底抽薪”降低其表达也是一种有效思路。BRD4抑制剂(如JQ1)可通过抑制转录激活来下调MYC水平。值得注意的是,BRD4与MYC的关系复杂,其自身也参与调控MYC蛋白稳定性。CDK7/9抑制剂(如THZ1、AZD4573)通过抑制转录延伸过程来减少MYC表达。在NSCLC中,THZ1还能下调PD-L1,增强免疫治疗效果。PI3K/AKT/mTOR通路抑制剂(如MK2206、Bimiralisib)则作用于MYC mRNA翻译层面。2.3 新兴力量:靶向蛋白降解与表观遗传调控
靶向蛋白降解(TPD)技术为解决“不可成药”问题带来了曙光。理论上,PROTAC和分子胶能降解任何蛋白。目前,虽无直接靶向MYC的PROTAC药物,但已有分子胶WBC100被报道可通过E3连接酶CHIP直接降解C-MYC蛋白,并在动物模型中有效抑制肿瘤生长。同时,通过降解BRD4来间接影响MYC的PROTAC药物(如MZ1、ARV-825)也显示出良好前景。此外,表观遗传调控疗法是另一个新兴方向。例如,mRNA疗法OTX-2002通过表观遗传调节在转录前下调MYC,目前正在进行针对MYC相关实体瘤的临床试验(NCT05497453)。三、核心策略与代表药物概览
下表汇总了文中提到的主要靶向MYC策略及其代表性药物或工具分子,直观展示了当前研发的格局。
作用机制/策略
代表药物/分子
研究阶段
关键特点/发现
干扰蛋白质相互作用
MYCMI-6/7, MYci975, Omomyc
临床前至Ⅱ期临床
直接阻断MYC-MAX二聚化;Omomyc具有细胞穿透能力并已进入临床。
调控MYC表达
JQ1 (BRD4i), THZ1 (CDK7i), AZD4573 (CDK9i)
临床前至Ⅱ期临床
通过抑制转录 machinery 间接下调MYC;THZ1可增强免疫治疗。
靶向蛋白降解 (TPD)
WBC100 (分子胶), ARV-825 (PROTAC)
临床前研究
WBC100可直接降解C-MYC;PROTAC类通过降解BRD4等间接起效。
表观遗传调控
OTX-2002 (mRNA疗法)
临床试验中 (NCT05497453)
在转录前水平下调MYC,针对肝细胞癌等实体瘤。四、总结与未来展望
靶向MYC的研发已从单一思路走向多策略并进。尽管挑战巨大,但进展显著:
策略多元化:从直接干扰互作、抑制表达、诱导降解到表观遗传重编程,形成了立体化的攻击网络。
技术突破:靶向蛋白降解技术,特别是分子胶(如WBC100),成功实现了对MYC蛋白的直接降解,为“不可成药”靶点提供了全新范式。
联合潜力:部分策略(如CDK7i THZ1)在下调MYC的同时能重塑免疫微环境,提示与免疫检查点抑制剂联合治疗的巨大潜力。
待解难题:多数药物仍处于临床前或早期临床阶段。脱靶效应、生物利用度、全身毒性以及如何克服MYC家族成员的功能冗余,仍是临床转化必须跨越的障碍。
笔者认为,未来的研究将更侧重于精准递送、优化药物设计以提高选择性,并探索基于生物标志物(如MYC扩增状态、特定下游通路激活)的个性化用药方案。同时,不同靶向策略之间的合理序贯或联合应用,有望成为攻克MYC驱动型肿瘤的关键。随着对MYC生物学网络理解的加深和药物研发技术的迭代,我们有理由期待,破解MYC“不可成药”魔咒的那一天正渐行渐近。
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