Sensitization effect and mechanism of FAP-targeted radioligand therapy combined with immune checkpoint inhibitors on microsatellite stable colorectal cancer
10.3760/cma.j.cn321828-20251013-00359
- VernacularTitle:FAP放射性配体治疗协同免疫检查点抑制剂对微卫星稳定型结直肠癌的增敏效应与机制探索
- Author:
Jianhao CHEN
1
;
Yangfan ZHOU
;
Yizhen PANG
;
Shan YU
;
Hua WU
;
Guoqiang SU
;
Liang ZHAO
;
Haojun CHEN
Author Information
1. 厦门大学附属第一医院核医学科及闽南PET中心，厦门 361003
- Publication Type:Journal Article
- Keywords:
Colorectal neoplasms;
Membrane proteins;
Gallium radioisotopes;
Lutetium;
Programmed cell death 1 receptor;
Mice;
Positron-emission tomography;
FAP
- From:
Chinese Journal of Nuclear Medicine and Molecular Imaging
2025;45(12):714-719
- CountryChina
- Language:Chinese
-
Abstract:
Objective:To explore the potential of the novel fibroblast activation protein (FAP)-targeted theranostic agent 68Ga/ 177Lu-1, 4, 7, 10-tetraazacyclododecane-1, 4, 7, 10-tetraacetic acid (DOTA)-2P (FAP inhibitor (FAPI)) 2 in microsatellite stable (MSS) colorectal cancer, and to evaluate the efficacy and underlying mechanism of 177Lu-DOTA-2P(FAPI) 2 in combination with immune checkpoint inhibitors (ICIs). Methods:This study was a randomized, parallel-group design. DOTA-2P(FAPI) 2 was labeled with 68Ga or 177Lu respectively. The binding performance of DOTA-2P(FAPI) 2 to FAP was validated through in vitro cell experiments. FAP-positive CT26-FAP tumor-bearing mouse model was constructed, and microPET imaging and biodistribution were performed. The in vivo antitumor efficacy was assessed for the 177Lu-DOTA-2P(FAPI) 2 monotherapy, α programmed death-ligand 1 (PD-L1) monotherapy, and the combination of 177Lu-DOTA-2P(FAPI) 2 with αPD-L1 therapy groups. Changes in the tumor microenvironment were analyzed using single-cell RNA sequencing to elucidate the mechanism of the combined treatment. Independent-sample t test was used to analyze data. Survival analysis was performed using the log-rank test. Results:The labeling yields of 68Ga/ 177Lu-DOTA-2P(FAPI) 2 were both >90%, with the radiochemical purities both >95%. In vitro cellular uptake and blocking assays showed that FAPI-46 significantly inhibited the binding of 68Ga-DOTA-2P(FAPI) 2 to FAP in CT26-FAP cells, with the cellular uptake values at 60min of (51.5±0.8)% and (1.0±0.3)%, respectively ( t=102.40, P<0.001). MicroPET imaging showed that the tumor uptake of 68Ga-DOTA-2P(FAPI) 2 remained stable even at 4 h post-injection, with a significantly higher uptake value compared to 68Ga-FAPI-46 ((7.3±1.6) vs (3.7±0.2) percentage activity of injection dose per gram of tissue (%ID/g); t=3.87, P=0.018). The biodistribution results indicated significant tumor uptake of 177Lu-DOTA-2P(FAPI) 2 even at 24 h post-injection ((4.30±0.52)%ID/g). The combination of 177Lu-DOTA-2P(FAPI) 2 and αPD-L1 achieved the 30-day survival rate of 100%, which was significantly superior to that of the control group (saline injection; χ2=9.53, P=0.002). Further mechanistic studies revealed that the combination therapy reprogramed the tumor microenvironment, enhanced anti-tumor intercellular communication, and activated signaling pathways such as Fas-FasL between T cells/natural killer (NK) cells and tumor cells, thereby synergistically inhibiting tumor progression. Conclusions:68Ga/ 177Lu-DOTA-2P(FAPI) 2 exhibits theranostic potential for MSS colorectal cancer. The combination of 177Lu-DOTA-2P(FAPI) 2 with ICIs may significantly prolong survival, demonstrating significant potential for clinical translation.
