Wang Yafang, Yao Mingyue, Li Cheng, Yang Kexin, Qin Xiaolong, Xu Lansong, Shi Shangxuan, Yu Chengcheng, Meng Xiangjun, Xie Chengying
Shanghai Institute for Advanced Immunochemical Studies, ShanghaiTech University, 393 Middle Huaxia Road, Shanghai, 201210, People's Republic of China.
Division of Life Sciences and Medicine, The First Affiliated Hospital of USTC (Anhui Provincial Hospital), University of Science and Technology of China, Hefei, Anhui, China.
Exp Hematol Oncol. 2023 Dec 16;12(1):105. doi: 10.1186/s40164-023-00466-3.
KRAS inhibitors (KRASi) AMG510 and MRTX849 have shown promising efficacy in clinical trials and been approved for the treatment of KRAS-mutant cancers. However, the emergence of therapy-related drug resistance limits their long-term potential. This study aimed to identify the critical mediators and develop overcoming strategies.
By using RNA sequencing, RT-qPCR and immunoblotting, we identified and validated the upregulation of c-Myc activity and the amplification of the long noncoding RNA ST8SIA6-AS1 in KRASi-resistant cells. The regulatory axis ST8SIA6-AS1/Polo-like kinase 1 (PLK1)/c-Myc was investigated by bioinformatics, RNA fluorescence in situ hybridization, RNA immunoprecipitation, RNA pull-down and chromatin immunoprecipitation. Gain/loss-of-function assays, cell viability assay, xenograft models, and IHC staining were conducted to evaluate the anti-cancer effects of co-inhibition of ST8SIA6-AS1/PLK1 pathway and KRAS both in vitro and in vivo.
KRASi sustainably decreased c-Myc levels in responsive cell lines but not in cell lines with intrinsic or acquired resistance to KRASi. PLK1 activation contributed to this ERK-independent c-Myc stability, which in turn directly induced PLK1 transcription, forming a positive feedback loop and conferring resistance to KRASi. ST8SIA6-AS1 was found significantly upregulated in resistant cells and facilitated the proliferation of KRAS-mutant cancers. ST8SIA6-AS1 bound to Aurora kinase A (Aurora A)/PLK1 and promoted Aurora A-mediated PLK1 phosphorylation. Concurrent targeting of KRAS and ST8SIA6-AS1/PLK1 signaling suppressed both ERK-dependent and -independent c-Myc expression, synergistically led to cell death and tumor regression and overcame KRASi resistance.
Our study deciphers that the axis of ST8SIA6-AS1/PLK1/c-Myc confers both intrinsic and acquired resistance to KRASi and represents a promising therapeutic target for combination strategies with KRASi in the treatment of KRAS-mutant cancers.
KRAS抑制剂（KRASi）AMG510和MRTX849在临床试验中已显示出有前景的疗效，并已被批准用于治疗KRAS突变型癌症。然而，治疗相关耐药性的出现限制了它们的长期潜力。本研究旨在确定关键介质并制定克服策略。
通过RNA测序、RT-qPCR和免疫印迹，我们在KRASi耐药细胞中鉴定并验证了c-Myc活性的上调以及长链非编码RNA ST8SIA6-AS1的扩增。通过生物信息学、RNA荧光原位杂交、RNA免疫沉淀、RNA下拉和染色质免疫沉淀研究了ST8SIA6-AS1/极光激酶样激酶1（PLK1）/c-Myc调控轴。进行了功能获得/丧失实验、细胞活力实验、异种移植模型和免疫组化染色，以评估在体外和体内联合抑制ST8SIA6-AS1/PLK1途径和KRAS的抗癌效果。
KRASi可持续降低敏感细胞系中的c-Myc水平，但在对KRASi具有固有抗性或获得性抗性的细胞系中则不然。PLK1激活促成了这种不依赖于细胞外调节蛋白激酶（ERK）的c-Myc稳定性，而这反过来又直接诱导PLK1转录，形成正反馈回路并赋予对KRASi的抗性。发现ST8SIA6-AS1在耐药细胞中显著上调，并促进KRAS突变型癌症的增殖。ST8SIA6-AS1与极光激酶A（Aurora A）/PLK1结合，并促进Aurora A介导的PLK1磷酸化。同时靶向KRAS和ST8SIA6-AS1/PLK1信号传导可抑制ERK依赖性和非依赖性c-Myc表达，协同导致细胞死亡和肿瘤消退，并克服KRASi耐药性。
我们的研究表明，ST8SIA6-AS1/PLK1/c-Myc轴赋予对KRASi的固有抗性和获得性抗性，并且是在治疗KRAS突变型癌症中与KRASi联合策略的一个有前景的治疗靶点。
