PO.ET03.01 · 实验与分子治疗
GSDMB在HER2扩增型结直肠癌中驱动cGAS-STING介导的免疫逃逸
GSDMB drives cGAS-STING-mediated immune evasion in HER2-amplified colorectal cancer
作者与单位 Authors & Affiliations
摘要 Abstract
中文摘要
背景：HER2扩增型转移性结直肠癌（CRC）是一种侵袭性疾病亚型，预后差且对标准治疗响应有限。其恶性行为和免疫逃逸的分子机制，尤其是参与肿瘤进展和免疫调节的特定基因及信号通路的作用，仍未得到充分阐明。本研究探讨了驱动HER2扩增型CRC肿瘤进展和免疫逃逸的生物学机制。
方法：我们在癌症基因组图谱（TCGA）队列中分析了GSDMB和HER2的表达、拷贝数变异（CNV）及患者生存，并比较了不同临床分期、BRAF突变状态和微卫星状态下的表达情况。开展了机制研究，包括RT-qPCR、蛋白质印迹、流式细胞术和免疫荧光，以评估GSDMB过表达对线粒体完整性、cGAS-STING通路激活及免疫相关分子表达的影响。进行了转录组分析以识别在GSDMB高表达肿瘤中富集的通路。
结果：GSDMB是HER2高表达CRC中最显著共富集的基因（FDR<0.001）。虽然GSDMB总体表达与生存无关（p=0.55），但高表达预示IV期患者生存较差（p=0.005）。GSDMB和HER2在染色体上相邻，HER2扩增始终伴随GSDMB共扩增；所有出现GSDMB CNV增益（6.4%）或缺失（0.3%）的患者均表现出相应的HER2 CNV变化。GSDMB表达在BRAF突变型（p<0.001）和MSI-H（p<0.001）肿瘤中显著升高。转录组分析显示GSDMB过表达与HER2信号通路和IFNalpha响应通路的富集相关（FDR<0.001）。实验验证表明，GSDMB过表达诱导线粒体膜孔形成，导致线粒体双链DNA持续、低水平地渗漏至细胞质，从而激活cGAS-STING通路并诱导慢性I型干扰素响应。这进而上调免疫检查点分子，削弱抗原呈递，并促进T细胞耗竭/耐受。
结论：GSDMB是HER2扩增型CRC中反复共扩增的基因，通过线粒体功能障碍和慢性cGAS-STING/I型干扰素信号重塑肿瘤免疫微环境，驱动免疫逃逸。尽管GSDMB单独在所有分期中不具有显著预后意义，但其升高的表达预示晚期转移性疾病的不良结局。这些发现凸显了GSDMB及其下游免疫通路作为HER2扩增型CRC中有前景的治疗靶点和预后生物标志物的价值。
查看英文原文 English abstract
Background: HER2-amplified metastatic colorectal cancer (CRC) represents an aggressive disease subtype with poor prognosis and limited response to standard therapies. The molecular mechanisms underlying its malignant behavior and immune evasion, particularly the contribution of specific genes and signaling pathways involved in tumor progression and immune regulation, remain insufficiently defined. This study investigated the biological mechanisms driving tumor progression and immune escape in HER2-amplified CRC.
Methods: We analyzed GSDMB and HER2 expression, copy number variations (CNVs), and patient survival in The Cancer Genome Atlas (TCGA) cohort, and compared expression across clinical stages, BRAF mutation status, and microsatellite status. Mechanistic studies, including RT-qPCR, western blotting, flow cytometry, and immunofluorescence, were conducted to evaluate the effects of GSDMB overexpression on mitochondrial integrity, activation of the cGAS-STING pathway, and immune-related molecule expression. Transcriptome analyses were conducted to identify pathways enriched in GSDMB-high tumors.
Results: GSDMB was the most significantly co-enriched gene in HER2-high CRC (FDR<0.001). Although overall GSDMB expression was not associated with survival ( p =0.55), high expression predicted poorer survival in stage IV patients ( p =0.005). GSDMB and HER2 are adjacent on the chromosome, and HER2 amplification was consistently accompanied by GSDMB co-amplification; all patients with GSDMB CNV gains (6.4%) or losses (0.3%) showed corresponding HER2 CNV changes. GSDMB expression was significantly elevated in BRAF-mutant ( p <0.001) and MSI-H ( p <0.001) tumors. Transcriptomic analyses revealed that GSDMB overexpression was associated with enrichment of HER2 signaling and IFNalpha Response pathways (FDR<0.001). Experimental validation demonstrated that GSDMB overexpression induced mitochondrial membrane pores, resulting in chronic, low-level leakage of mitochondrial double-stranded DNA into the cytoplasm, which activated the cGAS-STING pathway and induced chronic type I interferon responses. This, in turn, upregulated immune checkpoint molecules, impaired antigen presentation, and promoted T cell exhaustion/tolerance.
Conclusion: GSDMB is a recurrently co-amplified gene in HER2-amplified CRC and remodels the tumor immune microenvironment via mitochondrial dysfunction and chronic cGAS-STING/type I interferon signaling, driving immune evasion. Although GSDMB alone is not prognostically significant across all stages, it elevated expression predicts poor outcomes in advanced metastatic disease. These findings highlight GSDMB and its downstream immune pathways as promising therapeutic targets and prognostic biomarkers in HER2-amplified CRC.
利益披露 Disclosure
J. Weng, None.