Establishment of FAP-overexpressing Cells for FAP-targeted Theranostics

Objective Fibroblast activation protein(FAP)has been widely studied and exploited for its clinical applications.One of the difficulties in interpreting reports of FAP-targeted theranostics is due to the lack of accurate controls,making the results less specific and less confirmative.This study aimed to establish a pair of cell lines,in which one highly expresses FAP(HT1080-hFAP)and the other has no detectable FAP(HT1080-vec)as control,to accurately evaluate the specificity of the FAP-targeted theranostics in vitro and in vivo.Methods The cell lines of the experimental group(HT1080-hFAP)and no-load group(HT1080-vec)were obtained by molecular construction of the recombinant plasmid pIRES-hFAP.The expression of hFAP in HT1080 cells was detected by PCR,Western blotting and flow cytometry.CCK-8,Matrigel transwell invasion assay,scratch test,flow cytometry and immunofluorescence were used to verify the physiological function of FAP.The activities of human dipeptidyl peptidase(DPP)and human endopeptidase(EP)were detected by ELISA in HT1080-hFAP cells.PET imaging was performed in bilateral tumor-bearing nude mice models to evaluate the specificity of FAP.Results RT-PCR and Western blotting demonstrated the mRNA and protein expression of hFAP in HT1080-hFAP cells but not in HT1080-vec cells.Flow cytometry confirmed that nearly 95%of the HT1080-hFAP cells were FAP positive.The engineered hFAP on HT1080 cells had its ability to retain enzymatic activities and a variety of biological functions,including internalization,proliferation-,migration-,and invasion-promoting activities.The HT1080-hFAP xenografted tumors in nude mice bound and took up^(68)GA-FAPI-04 with superior selectivity.High image contrast and tumor-organ ratio were obtained by PET imaging.The HT1080-hFAP tumor retained the radiotracer for at least 60 min.Conclusion This pair of HT1080 cell lines was successfully established,making it feasible for accurate evaluation and visualization of therapeutic and diagnostic agents targeting the hFAP.

Preclinical evaluation and pilot clinical study of [^(18)F]AlF-labeled FAPI-tracer for PET imaging of cancer associated fibroblasts

In recent years,fibroblast activation protein(FAP)has emerged as an attractive target for the diagnosis and radiotherapy of cancers using FAP-specific radioligands.Herein,we aimed to design a novel^(18)Flabeled FAP tracer([^(18)F]Al F-P-FAPI)for FAP imaging and evaluated its potential for clinical application.The[^(18)F]Al F-P-FAPI novel tracer was prepared in an automated manner within 42 min with a non-decay corrected radiochemical yield of 32±6%(n=8).Among A549-FAP cells,[^(18)F]Al F-P-FAPI demonstrated specific uptake,rapid internalization,and low cellular efflux.Compared to the patent tracer[^(18)F]FAPI-42,[^(18)F]Al F-P-FAPI exhibited lower levels of cellular efflux in the A549-FAP cells and higher stability in vivo.Micro-PET imaging in the A549-FAP tumor model indicated higher specific tumor uptake of[^(18)F]Al F-P-FAPI(7.0±1.0%ID/g)compared to patent tracers[^(18)F]FAPI-42(3.2±0.6%ID/g)and[68 Ga]Ga-FAPI-04(2.7±0.5%ID/g).Furthermore,in an initial diagnostic application in a patient with nasopharyngeal cancer,[^(18)F]Al F-P-FAPI and[^(18)F]FDG PET/CT showed comparable results for both primary tumors and lymph node metastases.These results suggest that[^(18)F]Al F-P-FAPI can be conveniently prepared,with promising characteristics in the preclinical evaluation.The feasibility of FAP imaging was demonstrated using PET studies.

The FAPα-activated prodrug Z-GP-DAVLBH inhibits the growth and pulmonary metastasis of osteosarcoma cells by suppressing the AXL pathway

Osteosarcoma is a kind of bone tumor with highly proliferative and invasive properties,a high incidence of pulmonary metastasis and a poor prognosis.Chemotherapy is the mainstay of treatment for osteosarcoma.Currently,there are no molecular targeted drugs approved for osteosarcoma treatment,particularly effective drugs for osteosarcoma with pulmonary metastases.It has been reported that fibroblast activation protein alpha(FAPa)is upregulated in osteosarcoma and critically associated with osteosarcoma progression and metastasis,demonstrating that FAPa-targeted agents might be a promising therapeutic strategy for osteosarcoma.In the present study,we reported that the FAPa-activated vinblastine prodrug Z-GP-DAVLBH exhibited potent antitumor activities against FAPa-positive osteosarcoma cells in vitro and in vivo.Z-GP-DAVLBH inhibited the growth and induced the apoptosis of osteosarcoma cells.Importantly,it also decreased the migration and invasion capacities and reversed epithelial-mesenchymal transition(EMT)of osteosarcoma cells in vitro and suppressed pulmonary metastasis of osteosarcoma xenografts in vivo.Mechanistically,Z-GP-DAVLBH suppressed the AXL/AKT/GSK-3β/β-catenin pathway,leading to inhibition of the growth and metastatic spread of osteosarcoma cells.These findings demonstrate that Z-GP-DAVLBH is a promising agent for the treatment of FAPa-positive osteosarcoma,particularly osteosarcoma with pulmonary metastases.

The application of FAPI-targeted theranostics in pancreatic cancer:a narrative review

Pancreatic cancer is one of the most lethal malignancies in the world.Cancer-associated fibroblasts are one of the main components of tumor microenvironment in pancreatic cancer and play an essential role in tumor progression.Fibroblast activation protein that is expressed in specific subtypes of cancer-associated fibroblasts promotes tumor growth and is related to poor survival.Recent researches have preliminarily demonstrated a promising potential of radiopharmaceuticals targeting fibroblast activation protein in diagnosis and therapy of pancreatic cancer.This article comprehensively reviews the current development and clinical translation of fibroblast activation protein inhibitor-targeting radiopharmaceuticals in pancreatic cancer and provides significant perspectives for future investigations.