Baseline tumor features and peripheral blood immune dynamics that underlie efficacy in MSS metastatic colorectal cancer treated with regorafenib, ipilimumab, and nivolumab

Microsatellite-stable metastatic colorectal cancer (MSS mCRC) remains resistant to conventional immunotherapies, yet in a phase I trial the combination of regorafenib, ipilimumab, and nivolumab (RIN) demonstrated a 27.6% overall response rate and a median overall survival of 20 months, particularly benefiting patients without liver metastases. Correlative studies of tumor biopsies from eight patients and peripheral blood samples from 29 patients revealed that good responders had a more immunogenic tumor microenvironment (TME) at baseline, with enhanced cellular proliferation, active DNA repair pathways, and elevated STING pathway expression, along with a Th1-skewed cytokine profile in peripheral blood. Poor responders exhibited dysregulated inflammation, vascular remodeling, and T cells showing pathogen-response gene signatures indicative of chronic inflammation; in those with liver metastases, T cells showed immune senescence and metabolic hyperactivation. After RIN therapy, good responders displayed increased TME immune cell infiltration, upregulation of immune-related genes, marked expansion of previously low-frequency TCR clones in CD8 T cells, heightened naive T cell proliferation, and activation of immune and metabolic pathways. Poor responders initially showed transient increases in bulk CD8 T cells, NK cells, Th1 cytokine production, and reduced exhaustion markers but did not sustain meaningful TCR repertoire expansion. These findings underscore the potential of RIN to reshape the immunological landscape of MSS mCRC by modulating both TME and systemic immunity, highlighting the importance of predictive biomarkers to guide personalized therapeutic strategies, particularly for overcoming resistance in liver metastases. Overall design: RNA-seq profiling was performed on snap-frozen tumor biopsies collected at baseline and after 1 cycle of RIN treatment (4 weeks).

微卫星稳定型转移性结直肠癌（Microsatellite-stable metastatic colorectal cancer, MSS mCRC）对常规免疫治疗仍存在固有耐药性，但一项I期临床试验结果显示，瑞戈非尼（regorafenib）、伊匹木单抗（ipilimumab）与纳武利尤单抗（nivolumab）联合方案（简称RIN方案）的总缓解率达27.6%，中位总生存期为20个月，该方案尤其使无肝转移患者获益显著。
对8例患者的肿瘤活检组织与29例患者的外周血样本开展关联分析后发现，治疗应答良好的患者在基线阶段即拥有更具免疫原性的肿瘤微环境（tumor microenvironment, TME），具体表现为细胞增殖活性增强、DNA修复通路活化、STING通路（STING pathway）表达上调，且外周血呈现Th1偏向的细胞因子谱。
而治疗应答不佳的患者则存在炎症失调、血管重塑现象，其T细胞带有提示慢性炎症的病原体应答基因特征；伴肝转移的患者体内T细胞还表现出免疫衰老及代谢过度激活的表型。
经RIN方案治疗后，应答良好的患者可观察到以下改变：肿瘤微环境内免疫细胞浸润增加、免疫相关基因表达上调，CD8阳性T细胞中原本低频率的TCR克隆（TCR clones）显著扩增，初始T细胞增殖能力增强，免疫与代谢通路得以活化。
应答不佳的患者初期会出现总CD8 T细胞、NK细胞（natural killer cells, NK）数量及Th1细胞因子产生的短暂升高，耗竭标记物水平降低，但未能维持有效的T细胞受体库扩增。
上述研究结果凸显了RIN方案通过调控肿瘤微环境与系统免疫，重塑MSS mCRC免疫景观的潜在价值，同时强调了预测性生物标志物在指导个性化治疗策略——尤其是克服肝转移患者耐药性——中的重要意义。
整体实验设计：对基线及1周期RIN方案治疗（4周）后采集的速冻肿瘤活检组织进行RNA测序（RNA-seq）分析。