HNMT 上调通过与非小细胞肺癌中的 HER2 相互作用诱导癌症干细胞形成并赋予其抗氧化应激保护。

BACKGROUND: The treatment of non-small-cell lung cancer (NSCLC) involves platinum-based chemotherapy. It is typically accompanied by chemoresistance resulting from antioxidant properties conferred by cancer stem cells (CSCs). Human epidermal growth factor receptor 2 (HER2) enhances CSCs and antioxidant properties in cancers, including NSCLC. METHODS: Here, we elucidated the role of histamine N-methyltransferase (HNMT), a histamine metabolism enzyme significantly upregulated in NSCLC and coexpressed with HER2. HNMT expression in lung cancer tissues was determined using quantitative reverse transcription PCR (RT-qPCR). A publicly available dataset was used to determine HNMT's potential as an NSCLC target molecule. Immunohistochemistry and coimmunoprecipitation were used to determine HNMT-HER2 correlations and interactions, respectively. HNMT shRNA and overexpression plasmids were used to explore HNMT functions in vitro and in vivo. We also examined miRNAs that may target HNMT and investigated HNMT/HER2's role on NSCLC cells' antioxidant properties. Finally, how HNMT loss affects NSCLC cells' sensitivity to cisplatin was investigated. RESULTS: HNMT was significantly upregulated in human NSCLC tissues, conferred a worse prognosis, and was coexpressed with HER2. HNMT depletion and overexpression respectively decreased and increased cell proliferation, colony formation, tumorsphere formation, and CSCs marker expression. Coimmunoprecipitation analysis indicated that HNMT directly interacts with HER2. TARGETSCAN analysis revealed that HNMT is a miR-223 and miR-3065-5p target. TBHp treatment increased HER2 expression, whereas shHNMT disrupted the Nuclear factor erythroid 2-related factor 2 (Nrf2)/ hemeoxygenase-1 (HO-1)/HER2 axis and increased reactive oxygen species accumulation in NSCLC cells. Finally, shHNMT sensitized H441 cells to cisplatin treatment in vitro and in vivo. CONCLUSIONS: Therefore, HNMT upregulation in NSCLC cells may upregulate HER2 expression, increasing tumorigenicity and chemoresistance through CSCs maintenance and antioxidant properties. This newly discovered regulatory axis may aid in retarding NSCLC progression and chemoresistance.

背景：非小细胞肺癌（NSCLC）的治疗涉及铂类化疗。它通常伴随着由癌症干细胞（CSC）赋予的抗氧化特性引起的化疗耐药性。人表皮生长因子受体 2（HER2）增强了 CSC 和包括 NSCLC 在内的癌症的抗氧化特性。

方法：在这里，我们阐明了组氨酸 N-甲基转移酶（HNMT）的作用，HNMT 是一种在 NSCLC 中显著上调且与 HER2 共表达的组氨酸代谢酶。使用定量逆转录 PCR（RT-qPCR）测定肺癌组织中的 HNMT 表达。使用公开的数据集确定 HNMT 作为 NSCLC 靶分子的潜力。免疫组织化学和共免疫沉淀分别用于确定 HNMT-HER2 相关性和相互作用。使用 HNMT shRNA 和过表达质粒在体外和体内探索 HNMT 功能。我们还检查了可能靶向 HNMT 的 miRNAs，并研究了 HNMT/HER2 在 NSCLC 细胞抗氧化特性中的作用。最后，研究了 HNMT 缺失如何影响 NSCLC 细胞对顺铂的敏感性。

结果：HNMT 在人类 NSCLC 组织中显著上调，预示着更差的预后，并与 HER2 共表达。HNMT 耗竭和过表达分别降低和增加细胞增殖、集落形成、肿瘤球形成和 CSC 标志物表达。共免疫沉淀分析表明 HNMT 与 HER2 直接相互作用。TARGETSCAN 分析显示 HNMT 是 miR-223 和 miR-3065-5p 的靶标。TBHp 处理增加了 HER2 的表达，而 shHNMT 破坏了核因子红细胞 2 相关因子 2（Nrf2）/血红素加氧酶 1（HO-1）/HER2 轴并增加了 NSCLC 细胞中的活性氧积累。最后，shHNMT 在体外和体内使 H441 细胞对顺铂治疗敏感。

结论：因此，NSCLC 细胞中 HNMT 的上调可能通过 CSC 维持和抗氧化特性上调 HER2 的表达，从而增加肿瘤发生和化疗耐药性。这个新发现的调节轴可能有助于延缓 NSCLC 的进展和化疗耐药性。