PO.IM01.01 · 免疫学
NRAS突变型黑色素瘤中免疫激活的内在失败揭示了一种可靶向的检查点耐药机制
Intrinsic failure of immune activation in NRAS -mutant melanoma reveals a targetable mechanism of checkpoint resistance
作者与单位 Authors & Affiliations
摘要 Abstract
中文摘要
背景：黑色素瘤常由MAPK通路突变驱动，最突出的是BRAF（~50%）和NRAS（20-30%）。与受益于有效靶向治疗的BRAF突变型黑色素瘤不同，NRAS突变型黑色素瘤对MEK抑制应答不佳，且缺乏获批的靶向选择，导致结局较差。这一局限促进了基于免疫治疗的联合方案，然而对免疫检查点阻断（ICB）的应答仍不稳定。我们发现，NRAS突变型黑色素瘤在单独癌细胞中表现出高免疫基因活性，但在免疫刺激后可诱导性受抑，提示激活免疫程序存在内在失败，这可能限制ICB应答性。
方法：使用DESeq2和GSEA对TCGA-SKCM（肿瘤活检）和CCLE/DepMap（细胞系RNA-seq）数据集进行差异表达基因（DEG）和通路分析。通过比较细胞系内在数据集与肿瘤数据集之间的相对表达来定义"漂移基因"，选取方向性变化最大且校正p值显著（FDR<0.05，调节t检验）的基因。抗PD-1耐药细胞系通过体内序贯选择产生，包括对NRAS突变型黑色素瘤反复植入和抗PD-1治疗，直至肿瘤生长与未治疗对照相匹配。
结果：NRAS突变型黑色素瘤细胞系的RNA表达分析揭示了强烈的内在免疫基因活性；然而，这一活性在TCGA肿瘤中显著降低，提示肿瘤环境中可诱导性受抑。在T细胞炎症GEP基因（一种在对抗PD-1治疗有应答的肿瘤中高表达的既定免疫特征）中，MHC II类相关基因和CCL5降低最明显（≈1.3-1.4倍），而其余大多数保持稳定。与这些发现一致，NRAS突变型小鼠黑色素瘤细胞系表现出高基础免疫基因表达，但在干扰素gamma刺激（用于评估可诱导免疫基因应答）后诱导比野生型细胞弱近200倍。抗PD-1耐药模型反映了同样的模式，提示这种免疫无应答反映了NRAS突变型黑色素瘤的固有特征。
结论：NRAS突变型黑色素瘤的免疫治疗应答性仍不确定，凸显了界定其免疫特征的必要性。我们的发现表明，该亚型中的免疫无应答反映了一种根本的、细胞内在的局限，而非获得性结果，提示一种可靶向的机制以改善ICB结局。
查看英文原文 English abstract
Background: Melanoma is frequently driven by MAPK pathway mutations, most prominently BRAF (~50%) and NRAS (20-30%). Unlike BRAF -mutant melanoma, which benefits from effective targeted therapies, NRAS -mutant melanoma responds poorly to MEK inhibition and lacks approved targeted options, contributing to poorer outcomes. This limitation has encouraged immunotherapy-based combinations, yet responses to immune checkpoint blockade (ICB) remain variable. We found that NRAS -mutant melanoma exhibits high immune-gene activity in cancer cells alone but shows suppressed inducibility upon immune stimulation, indicating an intrinsic failure to activate immune programs that may limit ICB responsiveness.
Methods: DEG and pathway analyses were performed using DESeq2 and GSEA with TCGA-SKCM (tumor biopsy) and CCLE/DepMap (cell line RNA-seq) datasets. “Shift genes” were defined by comparing relative expression between cell line-intrinsic and tumor datasets, selecting genes with the largest directional changes and significant adjusted p-values (FDR < 0.05, moderated t-tests). Anti-PD-1-resistant cell lines were generated through serial in vivo selection involving repeated implantation and anti-PD-1 treatment of NRAS -mutant melanoma until tumor growth matched untreated controls.
Results: RNA expression analysis of NRAS -mutant melanoma cell lines revealed strong intrinsic immune-gene activity; however, this activity was markedly reduced in TCGA tumors, indicating suppressed inducibility in the tumor setting. Among the T cell-inflamed GEP genes-an established immune signature highly expressed in tumors responding to anti-PD-1 therapy-MHC class II-related genes and CCL5 showed the most pronounced reduction (≈1.3-1.4-fold), while most others remained stable. Consistent with these findings, NRAS -mutant murine melanoma cell lines exhibited high basal immune-gene expression but nearly 200-fold weaker induction following Interferon-gamma stimulation-used to evaluate inducible immune-gene responses-compared with wild-type cells. Anti-PD-1-resistant models mirrored this pattern, suggesting that such immune non-responsiveness reflects an inherent characteristic of NRAS -mutant melanoma.
Conclusion: The immunotherapy responsiveness of NRAS -mutant melanoma remains uncertain, underscoring the need to define its immune features. Our findings indicate that the immune unresponsiveness in this subtype reflects a fundamental, cell-intrinsic limitation rather than an acquired consequence, suggesting a targetable mechanism to improve ICB outcomes.
利益披露 Disclosure
I. Cho, None..
S. Kim, None..
J. Ahn, None..
S. Shin, None.