Kokolus Kathleen M, Huck Connor J, Connors Eoghan L, Cortes-Gomez Eduardo, Wang Jianmin, Obermajer Natasa, Basse Per H, Kalinski Pawel
Immunology, Roswell Park Comprehensive Cancer Center, Buffalo, New York, USA.
Biostatistics and Bioinformatics, Roswell Park Comprehensive Cancer Center, Buffalo, New York, USA.
J Immunother Cancer. 2025 Sep 18;13(9):e012307. doi: 10.1136/jitc-2025-012307.
Programmed cell death protein-1 (PD-1)-blocking immune checkpoint inhibitors (ICIs) are effective against highly immunogenic "hot" tumors containing high numbers of cytotoxic T-lymphocytes (CTLs), but not against poorly immunogenic "cold" tumors. We previously reported that the combination of TLR3 agonist rintatolimod with interferon (IFN)-α selectively induces CTL-attracting chemokines (CXCL9, CXCL10, CCL5) in the tumor microenvironment (TME), but not healthy tissues, raising the possibility of their systemic application to promote local CTL attraction to TME.
We used mouse colorectal cancer (CRC) cells implanted in syngeneic mice to test the effects of chemokine modulatory regimen (CKM) in combination with PD-1 blockade applied at different schedules. Tumor-bearing mice were treated and monitored for survival. In addition, we evaluated the reliance of CKM+αPD-1 treatment on various immune cell subsets. Finally, we observed treatment-induced changes in immune markers within TME.
Here, we report that both local or systemic application of CKM, a combination of rintatolimod and IFN-α, but not each of them individually, induces intratumoral CTL attractants and sensitizes PD-1-resistant MC38 and CT26 tumors to PD-1 blockade. The CKM/αPD-1 combination promotes intratumoral influx of BATF3-positive cDC1s and CTLs, inhibits tumor growth and prolongs survival, inducing cures in 20-100% of animals, depending on the tumor model and stage, and the route of delivery (local or systemic). CKM/αPD-1-treated mice develop local and systemic tumor-specific CTL responses and resistance to tumor re-challenge. The effectiveness of CKM requires its application at the time of or directly before PD-1 blockade and is strongly reduced by even a 24-hour delay in αPD-1 administration. CKM-driven intratumoral CTL accumulation and antitumor effects require host's BATF3cDC1s, CD8T-lymphocytes, and CXCR3 and CCR5 (receptors for CXCL9/CXCL10 and CCL5).
The ability of systemic CKM to eliminate the PD-1-resistance of cold tumors indicates that intratumoral CTL accumulation, rather than tumor immunogenicity, is the key factor limiting the therapeutic effectiveness of ICI. These data suggest a broad therapeutic potential of TME-reprogramming strategies.
程序性细胞死亡蛋白1（PD-1）阻断免疫检查点抑制剂（ICI）对含有大量细胞毒性T淋巴细胞（CTL）的高免疫原性“热”肿瘤有效，但对低免疫原性“冷”肿瘤无效。我们之前报道过，Toll样受体3激动剂瑞替莫德与干扰素（IFN）-α联合使用可在肿瘤微环境（TME）中选择性诱导吸引CTL的趋化因子（CXCL9、CXCL10、CCL5），而在健康组织中则不会，这增加了其全身应用以促进局部CTL向TME募集的可能性。
我们使用植入同基因小鼠体内的小鼠结直肠癌（CRC）细胞，来测试趋化因子调节方案（CKM）与不同给药方案的PD-1阻断联合使用的效果。对荷瘤小鼠进行治疗并监测其生存情况。此外，我们评估了CKM + αPD-1治疗对各种免疫细胞亚群的依赖性。最后，我们观察了TME内治疗诱导的免疫标志物变化。
在此，我们报告，瑞替莫德与IFN-α联合使用的CKM，无论是局部还是全身应用，而非单独使用其中任何一种，均可诱导肿瘤内CTL吸引剂，并使对PD-1耐药的MC38和CT26肿瘤对PD-1阻断敏感。CKM/αPD-1联合治疗可促进BATF3阳性cDC1和CTL向肿瘤内浸润，抑制肿瘤生长并延长生存期，根据肿瘤模型、阶段以及给药途径（局部或全身），可使20% - 100%的动物治愈。接受CKM/αPD-1治疗的小鼠产生局部和全身肿瘤特异性CTL反应以及对肿瘤再攻击的抵抗力。CKM的有效性要求在PD-1阻断时或之前直接应用，并且αPD-1给药延迟即使24小时也会使其效果大幅降低。CKM驱动的肿瘤内CTL积累和抗肿瘤作用需要宿主的BATF3 cDC1、CD8 T淋巴细胞以及CXCR3和CCR5（CXCL9/CXCL10和CCL5的受体）。
全身应用CKM消除冷肿瘤对PD-1耐药性的能力表明，肿瘤内CTL积累而非肿瘤免疫原性是限制ICI治疗效果的关键因素。这些数据表明TME重编程策略具有广泛的治疗潜力。
