The majority of hematopoietic cancers in adults are incurable and exhibit unpredictable remitting-relapsing patterns in response to various therapies. The proto-oncogene c-MYC has been associated with tumorigenesis, especially in hematological neoplasms. Therefore, targeting c-MYC is crucial to find effective, novel treatments for blood malignancies. To date, there are no clinically approved c-MYC inhibitors. In this study, we virtually screened 1578 Food and Drug Administration (FDA)-approved drugs from the ZINC15 database against c-MYC. The top 117 compounds from PyRx-based screening with the best binding affinities to c-MYC were subjected to molecular docking studies with AutoDock 4.2.6. Retinoids consist of synthetic and natural vitamin A derivatives. All-trans-retinoic acid (ATRA) were highly effective in hematological malignancies. In this study, adapalene, a third-generation retinoid usually used to treat acne vulgaris, was selected as a potent c-MYC inhibitor as it robustly bound to c-MYC with a lowest binding energy (LBE) of −7.27 kcal/mol, a predicted inhibition constant (pKi) of 4.69 µM, and a dissociation constant (Kdvalue) of 3.05 µM. Thus, we examined its impact on multiple myeloma (MM) cells in vitro and evaluated its efficiency in vivo using a xenograft tumor zebrafish model. We demonstrated that adapalene exerted substantial cytotoxicity against a panel of nine MM and two leukemic cell lines, with AMO1 cells being the most susceptible one (IC50= 1.76 ± 0.39 µM) and, hence, the focus of this work. Adapalene (0.5 × IC50, 1 × IC50, 2 × IC50) decreased c-MYC expression and transcriptional activity in AMO1 cells in a dose-dependent manner. An examination of the cell cycle revealed that adapalene halted the cells in the G2/M phase and increased the portion of cells in the sub-G0/G1phase after 48 and 72 h, indicating that cells failed to initiate mitosis, and consequently, cell death was triggered. Adapalene also increased the number of p-H3(Ser10) positive AMO1 cells, which is a further proof of its ability to prevent mitotic exit. Confocal imaging demonstrated that adapalene destroyed the tubulin network of U2OS cells stably transfected with a cDNA coding for α-tubulin-GFP, refraining the migration of malignant cells. Furthermore, adapalene induced DNA damage in AMO1 cells. It also induced apoptosis and autophagy, as demonstrated by flow cytometry and western blotting. Finally, adapalene impeded tumor growth in a xenograft tumor zebrafish model. In summary, the discovery of the vitamin A derivative adapalene as a c-MYC inhibitor reveals its potential as an avant-garde treatment for MM.
成人造血系统恶性肿瘤大多难以治愈，且对各类治疗呈现难以预测的缓解-复发模式。原癌基因c-MYC已被证实与肿瘤发生发展密切相关，尤其在血液系统肿瘤中作用显著。因此，靶向c-MYC对探索血液恶性肿瘤的新型有效治疗方案至关重要。目前尚无临床批准的c-MYC抑制剂。本研究通过虚拟筛选技术，从ZINC15数据库中的1578种美国食品药品监督管理局（FDA）批准药物中筛选靶向c-MYC的潜在化合物。基于PyRx平台筛选出与c-MYC结合亲和力最佳的117种化合物，并采用AutoDock 4.2.6进行分子对接研究。维甲酸类药物包含合成与天然维生素A衍生物，其中全反式维甲酸（ATRA）在血液恶性肿瘤治疗中疗效显著。本研究发现常用于治疗寻常痤疮的第三代维甲酸类药物阿达帕林，可作为强效c-MYC抑制剂，其与c-MYC的结合能最低（LBE=-7.27 kcal/mol），预测抑制常数（pKi）为4.69 µM，解离常数（Kd值）为3.05 µM。为此，我们在体外评估了阿达帕林对多发性骨髓瘤（MM）细胞的作用，并利用斑马鱼异种移植瘤模型进行体内药效验证。研究证实阿达帕林对9种MM细胞系及2种白血病细胞系均产生显著细胞毒性，其中AMO1细胞最为敏感（IC50=1.76±0.39 µM），故将其作为本研究重点。阿达帕林（0.5×IC50、1×IC50、2×IC50）能以剂量依赖性方式降低AMO1细胞中c-MYC表达及转录活性。细胞周期检测显示，阿达帕林处理48小时和72小时后可将细胞阻滞于G2/M期，并增加亚G0/G1期细胞比例，表明细胞有丝分裂启动受阻并最终引发细胞死亡。同时，阿达帕林能增加p-H3(Ser10)阳性AMO1细胞数量，进一步证实其可阻断有丝分裂退出进程。共聚焦成像显示，阿达帕林能破坏稳定转染α-微管蛋白-GFP编码cDNA的U2OS细胞微管网络，抑制恶性细胞迁移。此外，阿达帕林可诱导AMO1细胞DNA损伤，并通过流式细胞术与蛋白质印迹法证实其能同时诱导细胞凋亡与自噬。最终，斑马鱼异种移植瘤模型证实阿达帕林可有效抑制肿瘤生长。综上所述，维生素A衍生物阿达帕林作为c-MYC抑制剂的发现，揭示了其作为多发性骨髓瘤前沿治疗方案的潜在价值。
肿瘤(癌症)患者之家