Cai Weisong, Wu Sa, Lin Zehua, Ming Xiaoping, Yang Xiuping, Yang Minlan, Chen Xiong
Department of Otorhinolaryngology, Head and Neck Surgery, Zhongnan Hospital of Wuhan University, Wuhan, China.
Department of Gynaecology II, Maternal and Child Health Hospital of Hubei Province, TongjiMedical College, Huazhong University of Science and Technology, Wuhan, China.
Cancer Cell Int. 2024 Sep 8;24(1):307. doi: 10.1186/s12935-024-03494-z.
Hypoxia plays an important role in the chemotherapy resistance of nasopharyngeal carcinoma (NPC). Ferroptosis is a newly discovered form of programmed cell death and ferroptosis inducers showed promising therapeutic effects in some cancers. However, the sensibility of NPC cells to ferroptosis under the hypoxic microenvironment is still unclear, and this study was designed to clarify it.
NPC cells, treated with erastin, were placed in a normoxia or hypoxic environment (5% CO, 94% N and 1% O) at 37℃for 24 h. After exposed to hypoxia, ferroptosis-associated phenotypes were detected by CCK8, MDA, GSH, lipid ROS and Fe. The gene expression profiles of head and neck squamous cell carcinoma (HNSCC) tissues were downloaded from the TCGA database to screen construction molecule. BAP1 was screened out and its functions on erastin-induced ferroptosis in NPC cells were detected by knockdown of BAP1. Luciferase reporter assay and co-IP experiment were performed to explore the molecular mechanism. Finally, the tumour xenograft model was applied to further verify these results in vivo.
CCK8 assay showed that IC of NPC cells treated with erastin under hypoxia was significantly lower than that under normoxia. Hypoxia significantly increased the levels of lipid ROS and MDA, and decreased GSH content induced by erastin. A prognostic risk model for HNSCC with six ferroptosis-related genes was constructed and validated based on TCGA database. BAP1 was significantly up-regulated under hypoxia, and luciferase reporter assay showed that HIF-1α was an upstream transcription regulator of BAP1. Knockdown of BAP1 in NPC cells significantly increased the IC value of erastin under hypoxia and significantly ameliorated erastin-induced ferroptosis under hypoxia in aspect of lipid ROS, MDA content and GSH. Co-IP results showed that BAP1 mediated deubiquitination of H2A and decreased SLC7A11 expression. Finally, knockdown of BAP1 reduced sensitivity to erastin-induced ferroptosis in a tumour xenograft model. And the level of H2A was significantly decreased in xenograft tumors of BAP1 knockdown cells.
Hypoxia-induced BAP1 enhances erastin-induced ferroptosis in NPC by stabilizing H2A. Ferroptosis inducers targeting BAP1 may be an effective way to improve chemotherapy resistance in NPC, especially in the hypoxic microenvironment.
缺氧在鼻咽癌（NPC）的化疗耐药中起重要作用。铁死亡是一种新发现的程序性细胞死亡形式，铁死亡诱导剂在某些癌症中显示出有前景的治疗效果。然而，NPC细胞在缺氧微环境下对铁死亡的敏感性仍不清楚，本研究旨在阐明这一点。
用erastin处理的NPC细胞置于37℃的常氧或缺氧环境（5%CO₂、94%N₂和1%O₂）中24小时。暴露于缺氧环境后，通过CCK8、丙二醛（MDA）、谷胱甘肽（GSH）、脂质活性氧（ROS）和铁检测铁死亡相关表型。从TCGA数据库下载头颈部鳞状细胞癌（HNSCC）组织的基因表达谱以筛选构建分子。筛选出BAP1，并通过敲低BAP1检测其对NPC细胞中erastin诱导的铁死亡的作用。进行荧光素酶报告基因检测和免疫共沉淀（co-IP）实验以探索分子机制。最后，应用肿瘤异种移植模型在体内进一步验证这些结果。
CCK8检测显示，缺氧条件下用erastin处理的NPC细胞的半数抑制浓度（IC）显著低于常氧条件下的。缺氧显著增加脂质ROS和MDA水平，并降低erastin诱导的GSH含量。基于TCGA数据库构建并验证了一个包含六个铁死亡相关基因的HNSCC预后风险模型。缺氧条件下BAP1显著上调，荧光素酶报告基因检测表明缺氧诱导因子-1α（HIF-1α）是BAP1的上游转录调节因子。敲低NPC细胞中的BAP1显著增加缺氧条件下erastin的IC值，并在脂质ROS、MDA含量和GSH方面显著改善缺氧条件下erastin诱导的铁死亡。免疫共沉淀结果表明，BAP1介导组蛋白H2A的去泛素化并降低溶质载体家族7成员11（SLC7A11）的表达。最后，敲低BAP1降低了肿瘤异种移植模型中对erastin诱导的铁死亡的敏感性。敲低BAP1细胞的异种移植肿瘤中H2A水平显著降低。
缺氧诱导的BAP1通过稳定H2A增强erastin诱导的NPC铁死亡。靶向BAP1的铁死亡诱导剂可能是改善NPC化疗耐药的有效方法，尤其是在缺氧微环境中。
