Chung Yu-Han, Qian Qiu, Huang Hsin-Ying, Chiu Wen-Tai, Yang Chung-Shi, Tzeng Shun-Fen
Department of Life Sciences, College of Bioscience and Biotechnology, National Cheng Kung University, Tainan, Taiwan.
Institute of Biomedical Engineering and Nanomedicine, National Health Research Institutes, Miaoli, Taiwan.
Front Cell Neurosci. 2021 Oct 20;15:713336. doi: 10.3389/fncel.2021.713336. eCollection 2021.
Glioma, the most common subtype of primary brain tumor, is an aggressive and highly invasive neurologically tumor among human cancers. Interleukin-33 (IL-33) is considered as a dual functional cytokine, an alarmin upon tissue damage and a nuclear chromatin-associated protein. Despite that, IL-33 is known to foster the formation of the inflammatory tumor microenvironment and facilitate glioma progression, evidence showing nuclear IL-33 function is still poor. In this study using lentivirus-mediated IL-33 gene knockdown (IL33KD) and IL-33 overexpression (IL33oe) in rat C6 glioma cells and human glioma cell lines (U251MG and U87MG), we found that IL33oe-glioma cells had resistance to the insults of the alkylating agent, temozolomide (TMZ), possibly because of the increased expression of DNA repair genes (i.e., BRCA1, BRCA2, Rad51, FANCB, and FANCD) in IL33oe-glioma cells. Alternatively, examination of glioma nuclear shape from transmission electron microscopy (TEM) imaging analysis and immunofluorescence for histone protein H2A staining showed that IL33KD attenuated the abnormal cancerous nuclear characteristic, such as indentation, long clefts, and multiple nucleoids. Yet, IL33oe promoted the changes in glioma nuclear shapes, such as the formation of multiple lobes. We further found that histone proteins, H2A and H3, were reduced in IL33KD glioma cells. The non-histone DNA-binding nucleoproteins, the high mobility group A1 (HMGA1) and HMGA2, were also downregulated by IL33KD. In contrast, IL33oe increased H2A and H3 proteins and HMGA1 and HMGA2 in glioma cells. Altogether, the upregulation of nuclear IL-33 expression was along with an increase in the expression of DNA repair genes, contributing to the desensitization of glioma cells to DNA damaging agents. Moreover, nuclear IL-33 proteins in cooperation with chromatin-associated proteins regulate glioma nuclear structure, which might be crucial for glioma progression and malignancy.
胶质瘤是原发性脑肿瘤最常见的亚型，是人类癌症中一种侵袭性很强且具有高度侵袭性的神经肿瘤。白细胞介素-33（IL-33）被认为是一种双功能细胞因子，是组织损伤时的警报素和一种与核染色质相关的蛋白质。尽管如此，已知IL-33会促进炎性肿瘤微环境的形成并促进胶质瘤进展，但显示核IL-33功能的证据仍然不足。在本研究中，我们在大鼠C6胶质瘤细胞以及人胶质瘤细胞系（U251MG和U87MG）中使用慢病毒介导的IL-33基因敲低（IL33KD）和IL-33过表达（IL33oe），发现IL33oe胶质瘤细胞对烷化剂替莫唑胺（TMZ）的损伤具有抗性，这可能是因为IL33oe胶质瘤细胞中DNA修复基因（即BRCA1、BRCA2、Rad51、FANCB和FANCD）的表达增加。另外，通过透射电子显微镜（TEM）成像分析和组蛋白H2A染色的免疫荧光检查胶质瘤核形态，结果显示IL33KD减弱了异常的癌核特征，如凹陷、长裂缝和多个核仁。然而，IL33oe促进了胶质瘤核形态的改变，如多个叶的形成。我们进一步发现，IL33KD胶质瘤细胞中的组蛋白H2A和H3减少。非组蛋白DNA结合核蛋白高迁移率族蛋白A1（HMGA1）和HMGA2也被IL33KD下调。相反，IL33oe增加了胶质瘤细胞中的H2A和H3蛋白以及HMGA1和HMGA2。总之，核IL-33表达的上调与DNA修复基因表达的增加同时出现，这导致胶质瘤细胞对DNA损伤剂产生脱敏作用。此外，核IL-33蛋白与染色质相关蛋白协同调节胶质瘤核结构，这可能对胶质瘤的进展和恶性程度至关重要。
