Department of Otorhinolaryngology-Head and Neck Surgery, the First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, 710061, Shaanxi Province, China.
School of Future Technology, National Local Joint Engineering Research Center for Precision Surgery & Regenerative Medicine, Xi'an Jiaotong University, Xi'an City, 710061, Shaanxi Province, China.
Mol Cancer. 2023 Jul 1;22(1):103. doi: 10.1186/s12943-023-01811-0.
BACKGROUND: Tyrosine kinase inhibitors (TKIs) that specifically target mutational points in the EGFR gene have significantly reduced suffering and provided greater relief to patients with lung adenocarcinoma (LUAD). The third-generation EGFR-TKI, Osimertinib, has been successfully employed in clinical treatments to overcome resistance to both original and acquired T790M and L858R mutational points. Nevertheless, the issue of treatment failure response has emerged as an insurmountable problem. METHODS: By employing a combination of multiple and integrated approaches, we successfully identified a distinct population within the tumor group that plays a significant role in carcinogenesis, resistance, and recurrence. Our research suggests that addressing TKI resistance may involve targeting the renewal and repopulation of stem-like cells. To investigate the underlying mechanisms, we conducted RNA Microarray and m6A Epi-Transcriptomic Microarray analyses, followed by assessment of transcription factors. Additionally, we specifically designed a tag to detect the polypeptide circRNA-AA, and its expression was confirmed through m6A regulations. RESULTS: We initially identified unique molecular signatures present in cancer stem cells that contributed to poor therapeutic responses. Activation of the alternative Wnt pathway was found to sustain the renewal and resistant status of these cells. Through bioinformatics analysis and array studies, we observed a significant decrease in the expression of circFBXW7 in Osimertinib-resistant cell lines. Notably, the abnormal expression pattern of circFBXW7 determined the cellular response to Osimertinib. Functional investigations revealed that circFBXW7 inhibits the renewal of cancer stem cells and resensitizes both resistant LUAD cells and stem cells to Osimertinib. In terms of the underlying mechanism, we discovered that circFBXW7 can be translated into short polypeptides known as circFBXW7-185AA. These polypeptides interact with β-catenin in an m6A-dependent manner. This interaction leads to reduced stability of β-catenin by inducing subsequent ubiquitination, thereby suppressing the activation of canonical Wnt signaling. Additionally, we predicted that the m6A reader, YTHDF3, shares common binding sites with hsa-Let-7d-5p. Enforced expression of Let-7d post-transcriptionally decreases the levels of YTHDF3. The repression of Let-7d by Wnt signaling releases the stimulation of m6A modification by YTHDF3, promoting the translation of circFBXW7-185AA. This creates a positive feedback loop contributing to the cascade of cancer initiation and promotion. CONCLUSIONS: Our bench study, in vivo experiments, and clinical validation have unequivocally shown that circFBXW7 effectively inhibits the abilities of LUAD stem cells and reverses resistance to TKIs by modulating Wnt pathway functions through the action of circFBXW7-185AA on β-catenin ubiquitination and inhibition. The regulatory role of circRNA in Osimertinib treatment has been rarely reported, and our findings reveal that this process operates under the influence of m6A modification. These results highlight the tremendous potential of this approach in enhancing therapeutic strategies and overcoming resistance to multiple TKI treatments.
背景:针对 EGFR 基因突变的酪氨酸激酶抑制剂(TKIs)显著减轻了肺腺癌(LUAD)患者的痛苦,并提供了更大的缓解。第三代 EGFR-TKI 奥希替尼已成功应用于临床治疗,克服了对原始和获得性 T790M 和 L858R 突变点的耐药性。然而,治疗失败反应的问题已经成为一个不可逾越的问题。
方法:通过采用多种综合方法,我们成功地在肿瘤组中确定了一个在致癌、耐药和复发中起重要作用的独特群体。我们的研究表明,解决 TKI 耐药性可能涉及靶向干细胞样细胞的更新和再群体化。为了研究潜在机制,我们进行了 RNA 微阵列和 m6A 表观转录组微阵列分析,随后评估了转录因子。此外,我们专门设计了一个标记来检测多肽 circRNA-AA,并且通过 m6A 调节来确认其表达。
结果:我们最初在癌症干细胞中发现了导致治疗反应不良的独特分子特征。发现替代 Wnt 途径的激活维持了这些细胞的更新和耐药状态。通过生物信息学分析和阵列研究,我们观察到奥希替尼耐药细胞系中 circFBXW7 的表达显著降低。值得注意的是,circFBXW7 的异常表达模式决定了细胞对奥希替尼的反应。功能研究表明,circFBXW7 抑制了癌症干细胞的更新,并使耐药 LUAD 细胞和干细胞对奥希替尼重新敏感。在潜在机制方面,我们发现 circFBXW7 可以被翻译成称为 circFBXW7-185AA 的短多肽。这些多肽以 m6A 依赖的方式与β-catenin 相互作用。这种相互作用通过诱导随后的泛素化来降低β-catenin 的稳定性,从而抑制经典 Wnt 信号的激活。此外,我们预测 m6A 阅读器 YTHDF3 与 hsa-Let-7d-5p 共享共同的结合位点。Let-7d 的过表达在转录后降低了 YTHDF3 的水平。Wnt 信号对 Let-7d 的抑制释放了 YTHDF3 对 m6A 修饰的刺激,促进了 circFBXW7-185AA 的翻译。这形成了一个正反馈回路,有助于癌症起始和促进的级联反应。
结论:我们的基础研究、体内实验和临床验证都明确表明,circFBXW7 通过 circFBXW7-185AA 对β-catenin 泛素化和抑制作用调节 Wnt 途径功能,有效抑制 LUAD 干细胞的能力,并逆转对 TKIs 的耐药性。circRNA 在奥希替尼治疗中的调节作用很少有报道,我们的研究结果表明,这一过程在 m6A 修饰的影响下进行。这些结果突出了该方法在增强治疗策略和克服多种 TKI 治疗耐药性方面的巨大潜力。
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