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Objective:To develop a tetramer probe targeting fibroblast activation protein (FAP), named 1, 4, 7, 10-tetraazacyclododecane-1, 4, 7, 10-tetraacetic acid (DOTA)-4P(FAP inhibitor (FAPI)) 4, evaluate its biodistribution and PET image in FAP-positive-tumor bearing nude mice, and explore its feasibility as a novel radio-regent for treatment of FAP-positive tumor. Methods:FAP tetramer probe was constructed on the FAPI-46 motif with four mini-polyethylene glycol (PEG)(PEG 3) spacers between the four FAPI motifs, denoted as 4P(FAPI) 4. DOTA was used as the chelator for radiolabeling with 68Ga and 177Lu. The FAP binding characteristics were test by in vitro cell competitive binding experiment. Small-animal PET, in vivo biodistribution, and radionuclide targeting therapy were performed in HT-1080-FAP tumor bearing nude mice ( n=39). Independent-sample t test was performed to analyze tumor uptake data, and two-factor repeated measures analysis of variance was utilized to compare tumor volume data in radioactive isotope therapy. Results:Cell experiment showed that FAPI-tetramer and FAPI-monomer had similar half maximal inhibitory concentration values (3.29 and 2.15 nmol/L). 68Ga/ 177Lu radiolabeled FAPI-tetramer had better tumor uptake and retention than FAPI-monomer in small-animal PET and in vivo biodistribution experiment, with the tumor uptake for 177Lu-DOTA-4P(FAPI) 4 and 177Lu-FAPI-46 at 48 h of (18.72±1.32) vs (2.72±1.20) percentage activity of injection dose per gram of tissue (%ID/g) ( t=15.55, P<0.001). 177Lu-DOTA-4P(FAPI) 4 group showed best anti-tumor efficacy compared with 177Lu-FAPI-46 and control group in radionuclide targeting therapy. On the 2nd day after the start of treatment, the tumor volume in the tetramer treatment group was significantly smaller than that in the control group (mean difference 67.19 mm 3, P=0.049); on the 14th day after the start of treatment, the tumor volume in the tetramer treatment group was significantly smaller than that in the monomer treatment group (mean difference 414.33 mm 3, P=0.005). Conclusion:FAPI-tetramer can improve tumor uptake and retention ability compared with FAPI-46, and 177Lu-DOTA-4P(FAPI) 4 can be a promising radio-agent for FAP-positive tumor therapy.
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Objective:To investigate the clinical utility of 68Ga-labeled fibroblast activation protein inhibitor (FAPI) PET/CT in the detection of primary and metastatic gastric signet-ring cell carcinoma (GSRCC) and compared the results with those of 18F-FDG PET/CT. Methods:A total of 21 patients (10 males, 11 females, average age 52 years) with primary and metastatic GSRCC who underwent 68Ga-FAPI and 18F-FDG PET/CT at the First Affiliated Hospital of Xiamen University from June 2020 to May 2022 were retrospectively analyzed. Pathological results of surgery and (or) biopsy were used as the " gold standard" for final diagnosis. In cases whose surgery or tissue biopsies were not available, clinical and radiographic follow-up results were used as the reference standards. Wilcoxon signed-rank test was used to compare the SUV max of 18F-FDG and 68Ga-FAPI. McNemar χ2 test was used to compare the detection rate between 18F-FDG and 68Ga-FAPI PET/CT. Results:68Ga-FAPI PET/CT showed higher SUV max than 18F-FDG in primary tumors (5.3(2.4, 15.7) vs 2.4(1.8, 2.5); z=2.31, P=0.021), local recurrences (7.8(6.0, 8.9) vs 2.4(1.9, 3.4); z=2.20, P=0.028), lymph nodes metastases (7.7(4.5, 12.2) vs 2.4(1.9, 3.6); z=6.01, P<0.001) and bone/visceral metastases (6.7(5.3, 11.1) vs 2.4(2.0, 3.4); z=11.36, P<0.001). Regarding diagnostic accuracy, 68Ga-FAPI PET/CT showed higher sensitivities than 18F-FDG for primary tumors (7/9 vs 2/9; χ2=3.20, P=0.063) and local recurrences (7/7 vs 2/7; χ2=3.20, P=0.063). It also demonstrated higher lesion detection rates than 18F-FDG for suspicious lymph node metastases (86%(65/76) vs 32%(24/76); χ2=31.37, P<0.001) and bone/visceral metastases (99%(184/185) vs 39%(73/185); χ2=107.08, P<0.001). Conclusions:68Ga-FAPI PET/CT showed higher tumor uptake and lesion detection rate than 18F-FDG in the primary and metastatic GSRCC. 68Ga-FAPI PET/CT demonstrates good diagnostic performance for tumor detection, staging, and restaging of GSRCC, which is helpful to further guide clinical treatment strategy.
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Objective:To investigate the therapeutic efficacy and potential mechanisms of integrin α vβ 3-targeted radionuclide therapy (TRT) in combination with anti-programmed cell death protein ligand 1 (PD-L1) immunotherapy. Methods:Integrin α vβ 3-targeted molecule Arg-Gly-Asp (RGD) was conjugated with Evans blue (EB) and then labeled with 177Lu to obtain 177Lu-EB-RGD. The radioactivity and radiochemical purity were determined. MicroSPECT imaging, biodistribution, and in vivo therapeutic efficacy were subsequently performed in MC38 murine colon cancer models. Volume of tumor and body mass of mice were observed to assess the therapeutic efficacy and safety ( n=9 in each group). Flow cytometry was used to evaluate therapy response of saline-treated (control, group A), 18.5 MBq 177Lu-EB-RGD-treated (group B), 10 mg/kg PD-L1 antibody-treated (group C), TRT combined with immunotherapy-treated (group D, 18.5 MBq 177Lu-EB-RGD and 10 mg/kg PD-L1 antibody) mice and alterations in tumor microenvironment (PD-L1 + immune cells, CD8 + T cells and regulatory T cells). Independent-sample t test and repeated measures analysis of variance were used for data analysis. Results:The radioactivity of 177Lu-EB-RGD was (55.85±14.00) GBq/μmol. SPECT imaging clearly visualized the MC38 tumors in mice models with high uptake and long retention time, the tumor/muscle ratio reached 14.87±0.88 at 24 h postinjection, while less uptake and retention in normal tissues. Tumor uptake of 177Lu-EB-RGD was significantly higher than that of 177Lu-RGD 4 h post-injection ((12.00±1.60) vs (3.69±0.37) %ID/g; t=8.63, P<0.01). The efficacy results between each treatment group was significantly different ( F=7.32, P=0.03) at day 6 post-treatment. The combination therapy showed the most outstanding anti-tumor efficacy with 7/9 mice showed complete response. Flow cytometry results showed that TRT up-regulated the PD-L1 expression significantly, namely, PD-L1 + immune cells in group B and group A were significantly different (CD45 + /PD-L1: 2.34% vs 0.95%, CD11b + /PD-L1: 2.41% vs 0.66%; t values: 11.17 and 8.70, both P<0.01); immunotherapy and combination therapy dramatically stimulated the infiltration of CD8 + T cells (2.07% vs 0.26%, 2.71% vs 0.26%; t values: 4.10 and 6.03, both P<0.05). Conclusion:TRT in combination with immunotherapy synergistically enhance anti-tumor efficacy, which is expected to play a role in the treatment of patients with advanced tumor where TRT can be applied.
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Objective:To develop a novel α vβ 3-targeted theranostic agent 177Lu-Evans blue (EB)-Arg-Gly-Asp (RGD) and evaluate its value for SPECT imaging and targeted radionuclide therapy in the non-small cell lung cancer (NSCLC)-patient-derived xenografts (PDX). Methods:The α vβ 3-targeted molecule RGD was conjugated with the albumin binding moiety EB to obtain EB-RGD, and EB-RGD was further conjugated with the chelator 1, 4, 7, 10-tetraazacyclododecane-1, 4, 7, 10-tetraacetic acid (DOTA) for 177Lu radiolabeling. NSCLC-PDX mice models ( n=68) were established. 177Lu-EB-RGD SPECT imaging, biodistribution study were performed in 28 PDX mice models after being injected with 177Lu-EB-RGD or 177Lu-RGD. Targeted radionuclide therapy were subsequently performed in NSCLC-PDX mice models, saline group (group A), 18.5 MBq 177Lu-RGD group (group B), 18.5 MBq 177Lu-EB-RGD group (group C), 29.6 MBq 177Lu-EB-RGD group (group D), n=10 in each group; tumor volumes of PDX mice models in each group were observed within 50 d. Differences between 2 groups were compared using independent-sample t test. Results:177Lu-EB-RGD was radiolabeled at a specific activity of (55±14) GBq/μmol, with a radiochemical yield of more than 95% and a radiochemical purity of more than 95%. Regarding the SPECT imaging, tumors in NSCLC-PDX mice were clearly observed from 4 to 96 h post-injection and the tumor to muscle ratio (T/M) reached 7.34±0.67, 14.63±3.82, 15.69±3.58 and 15.99±5.42 at 4, 24, 72, 96 h post-injection, respectively. Biodistribution study further confirmed the findings from SPECT imaging, and the tumor uptake of 177Lu-EB-RGD were markedly increased compared to 177Lu-RGD 4 h post-injection ((10.15±1.17) vs (3.30±1.47) percent injection dose per gram (%ID/g); t=18.60, P<0.05). Regarding targeted radiotherapy, the tumor volumes were quickly increased within 50 d after treatment in group A and B, while the tumor volumes were decreased in group C and D, until the tumors in group C and D disappeared at the 28th day after initial treatment with no sign of recurrence during the observation period. Conclusions:177Lu-EB-RGD can target α vβ 3-positive NSCLC-PDX with intense tumor to background ratio and strong tumor inhibition efficacy. The preclinical data suggests that 177Lu-EB-RGD may be an effective new treatment option for advanced NSCLC patients with resistance or ineffective results for targeted therapy.
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Objective To investigate the value of 18F-FDG PET/CT in the phasing and grading of renal cell carcinoma (RCC) complicated with vena cava tumor thrombus (VCTT).Methods From December 2011 to September 2015,a total of 72 patients (52 males,20 females,age:36-74 years) were enrolled in this retrospectively study.All patients underwent 18F-FDG PET/CT and contrast-enhanced CT studies,and were diagnosed as RCC.The RCC patients combined with VCTT were classified by Mayo-level.Wilcoxon rank sum test was used to compare the grading of VCTT by PET/CT and contrast-enhanced CT.NM staging on abdominal area level was performed and the results were compared with x2 test.Results VCTT was identified in 18 RCC patients and the grading results by PET/CT were as follows:9 cases in Level 0,4 cases in Level Ⅰ,2 cases in Level Ⅱ,1 case in Level Ⅲ,and 2 cases in Level Ⅳ.When evaluated by PET/CT,20 cases were in N0M0,21 were in N1M0,9 were in N0M1,and 22 were in N1M1.NM staging results by contrast-enhanced CT were as follows:50 cases in N0M0,10 in N1M0,10 in N0M1,and 2 in N1M1.In addition,2 N1 and 2 M1 were found by the whole body PET/CT.The classification results of VCTT and staging of abdominal level by PET/CT were significantly better than those by contrast-enhanced CT (z=-2.462,P＜0.05;x2=32.806,P＜0.01).Conclusion 18F-FDG PET/CT is not only valuable for detecting primary RCC and local metastasis,but also useful for finding where the VCTT extends,which is conducive to therapeutic planning and further clinical treatment.