Fibroblast Activation Protein (FAP)-Targeted CAR-T Cells: Launching an Attack on Tumor Stroma.
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ABSTRACT:
SUBMITTER: Bughda R
PROVIDER: S-EPMC8354246 | biostudies-literature | 2021
REPOSITORIES: biostudies-literature
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Fibroblast Activation Protein (FAP)-Targeted CAR-T Cells: Launching an Attack on Tumor Stroma.
Bughda Reyisa R Dimou Paraskevi P D'Souza Reena R RR Klampatsa Astero A
ImmunoTargets and therapy 20210805
Fibroblast activation protein (FAP) is a membrane protease that is highly expressed by cancer-associated fibroblasts (CAFs). FAP can modulate the tumor microenvironment (TME) by remodeling the extracellular matrix (ECM), and its overexpression on CAFs is associated with poor prognosis in various cancers. The TME is in part accountable for the limited efficacy of chimeric antigen receptor (CAR)-T cell therapy in treatment of solid tumors. Targeting FAP with CAR-T cells is one of the strategies be ...[more]
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Project description:Purpose: Fibroblast activation protein (FAP) is overexpressed in cancer-associated fibroblasts and is an interesting target for cancer immune therapy, with prior studies indicating a potential to affect the tumor stroma. Our aim was to extend this earlier work through the development of a novel FAP immunogen with improved capacity to break tolerance for use in combination with tumor antigen vaccines.Experimental Design: We used a synthetic consensus (SynCon) sequence approach to provide MHC class II help to support breaking of tolerance. We evaluated immune responses and antitumor activity of this novel FAP vaccine in preclinical studies, and correlated these findings to patient data.Results: This SynCon FAP DNA vaccine was capable of breaking tolerance and inducing both CD8+ and CD4+ immune responses. In genetically diverse, outbred mice, the SynCon FAP DNA vaccine was superior at breaking tolerance compared with a native mouse FAP immunogen. In several tumor models, the SynCon FAP DNA vaccine synergized with other tumor antigen-specific DNA vaccines to enhance antitumor immunity. Evaluation of the tumor microenvironment showed increased CD8+ T-cell infiltration and a decreased macrophage infiltration driven by FAP immunization. We extended this to patient data from The Cancer Genome Atlas, where we find high FAP expression correlates with high macrophage and low CD8+ T-cell infiltration.Conclusions: These results suggest that immune therapy targeting tumor antigens in combination with a microconsensus FAP vaccine provides two-fisted punch-inducing responses that target both the tumor microenvironment and tumor cells directly. Clin Cancer Res; 24(5); 1190-201. ©2018 AACR.
| S-EPMC5844837 | biostudies-literature
Project description:PurposeFibroblast activation protein (FAP) is a membrane-bound protease that has limited expression in normal adult tissues but is highly expressed in the tumor microenvironment of many solid cancers. FAP-2286 is a FAP-binding peptide coupled to a radionuclide chelator that is currently being investigated in patients as an imaging and therapeutic agent. The potency, selectivity, and efficacy of FAP-2286 were evaluated in preclinical studies.MethodsFAP expression analysis was performed by immunohistochemistry and autoradiography on primary human cancer specimens. FAP-2286 was assessed in biochemical and cellular assays and in in vivo imaging and efficacy studies, and was further evaluated against FAPI-46, a small molecule-based FAP-targeting agent.ResultsImmunohistochemistry confirmed elevated levels of FAP expression in multiple tumor types including pancreatic, breast, and sarcoma, which correlated with FAP binding by FAP-2286 autoradiography. FAP-2286 and its metal complexes demonstrated high affinity to FAP recombinant protein and cell surface FAP expressed on fibroblasts. Biodistribution studies in mice showed rapid and persistent uptake of 68Ga-FAP-2286, 111In-FAP-2286, and 177Lu-FAP-2286 in FAP-positive tumors, with renal clearance and minimal uptake in normal tissues. 177Lu-FAP-2286 exhibited antitumor activity in FAP-expressing HEK293 tumors and sarcoma patient-derived xenografts, with no significant weight loss. In addition, FAP-2286 maintained longer tumor retention and suppression in comparison to FAPI-46.ConclusionIn preclinical models, radiolabeled FAP-2286 demonstrated high tumor uptake and retention, as well as potent efficacy in FAP-positive tumors. These results support clinical development of 68Ga-FAP-2286 for imaging and 177Lu-FAP-2286 for therapeutic use in a broad spectrum of FAP-positive tumors.
| S-EPMC9399058 | biostudies-literature
Project description:BackgroundCancer-associated fibroblasts (CAFs) can strongly modulate the response to therapy of malignant tumor cells, facilitating their continuous proliferation and invading behaviors. In this context, several efforts were made in identifying the fibroblast activation protein (FAP) as a CAF recognizer and in designing FAP-specific PET radiotracers (as 68Ga-FAPI) along with FAP-specific therapeutic radioligands. Herein, we review different clinical studies using the various FAP-specific radioligands as novel theranostic agents in a wide range of oncologic and nononcologic indications.MethodsA comprehensive systematic search was conducted on the PubMed and Scopus databases to find relevant published articles concerning the FAP-specific PET imaging as well as the FAP-specific radionuclide therapy in patients with oncologic and nononcologic indications. The enrolled studies were dichotomized into oncologic and nononcologic categories, and the required data were extracted by precisely reviewing the whole text of each eligible study. A meta-analysis was also performed comparing the detection rates of 68Ga-FAPI vs. 18F-FDG PET/CT using odds ratio (OR) and risk difference as outcome measures.ResultsOf the initial 364 relevant papers, 49 eligible articles (1479 patients) and 55 case reports were enrolled in our systematic review. These studies observed high radiolabeled FAPI avidity as early as 10 minutes after administration in primary sites of various malignant tumors. Based on the meta-analysis which was done on the reported detection rates of the 68Ga-FAPI and 18F-FDG PET/CT scans, the highest OR belonged to the primary lesion detection rate of gastrointestinal tumors (OR = 32.079, 95% CI: 4.001-257.212; p = 0.001) with low heterogeneity (I2 = 0%). The corresponding value of the nodal metastases belonged to hepatobiliary tumors (OR = 11.609, 95% CI: 1.888-71.365; p = 0.008) with low heterogeneity (I2 = 0%). For distant metastases, the highest estimated OR belonged to nasopharyngeal carcinomas (OR = 77.451, 95% CI: 7.323-819.201; p < 0.001) with low heterogeneity (I2 = 0%).ConclusionsThe outperformance of 68Ga-FAPI PET/CT over 18F-FDG PET/CT in identifying certain primary tumors as well as in detecting their metastatic lesions may open indications for evaluation of cases with inconclusive 18F-FDG PET/CT findings. What needs to be emphasized is that the false-positive results might be problematic and must be taken into account in 68Ga-FAPI PET/CT interpretation. More clarification on the role of FAPI radioligands in oncologic imaging, radionuclide therapy, and radiotherapy treatment planning is therefore required.
| S-EPMC8888077 | biostudies-literature
Project description:Several radiopharmaceuticals targeting fibroblast activation protein (FAP) based on the highly potent FAP inhibitor UAMC1110 are currently under investigation. Pre-clinical as well as clinical research exhibited the potential of these imaging agents. However, the monomeric small molecules seemed to have a short retention time in the tumor in combination with fast renal clearance. Therefore, our strategy was to develop homodimeric systems having two FAP inhibitors to improve residence time and tumor accumulation. The homodimers with two squaramide coupled FAP inhibitor conjugates DOTA.(SA.FAPi)2 and DOTAGA.(SA.FAPi)2 were synthesized and radiochemically evaluated with gallium-68. [68Ga]Ga-DOTAGA.(SA.FAPi)2 was tested for its in vitro stability, lipophilicity and affinity properties. In addition, human PET/CT scans were performed for [68Ga]Ga-DOTAGA.(SA.FAPi)2 with a head-to-head comparison with [68Ga]Ga-DOTA.SA.FAPi and [18F]FDG. Labeling with gallium-68 demonstrated high radiochemical yields. Inhibition measurements revealed excellent affinity and selectivity with low nanomolar IC50 values for FAP. In PET/CT human studies, significantly higher tumor uptake as well as longer tumor retention could be observed for [68Ga]Ga-DOTAGA.(SA.FAPi)2 compared to [68Ga]Ga-DOTA.SA.FAPi. Therefore, the introduction of the dimer led to an advance in human PET imaging indicated by increased tumor accumulation and prolonged retention times in vivo and thus, the use of dimeric structures could be the next step towards prolonged uptake of FAP inhibitors resulting in radiotherapeutic analogs of FAP inhibitors.
| S-EPMC8727881 | biostudies-literature
Project description:BackgroundOncolytic virus (OV)-based therapies have an emerging role in the treatment of solid tumors, involving both direct cell lysis and immunogenic cell death. Nonetheless, tumor-associated stroma limits the efficacy of oncolytic viruses by forming a barrier that blocks efficient viral penetration and spread. The stroma also plays a critical role in progression, immunosuppression and invasiveness of cancer. Fibroblast activation protein-α (FAP) is highly overexpressed in cancer-associated fibroblasts (CAFs), the main cellular component of tumor stroma, and in this study we assessed whether arming oncolytic adenovirus (OAd) with a FAP-targeting Bispecific T-cell Engager (FBiTE) could retarget infiltrated lymphocytes towards CAFs, enhancing viral spread and T cell-mediated cytotoxicity against the tumor stroma to improve therapeutic activity.MethodsThe bispecific T-cell Engager against FAP was constructed using an anti-human CD3 single-chain variable fragment (scFv) linked to an anti-murine and human FAP scFv. This FBiTE was inserted in the oncolytic adenovirus ICOVIR15K under the control of the major late promoter, generating the ICO15K-FBiTE. ICO15K-FBiTE replication and potency were assessed in HT1080 and A549 tumor cell lines. The expression of the FBiTE and the activation and proliferation of T cells that induced along with the T cell-mediated cytotoxicity of CAFs were evaluated by flow cytometry in vitro. In vivo, T-cell biodistribution and antitumor efficacy studies were conducted in NOD/scid/IL2rg-/- (NSG) mice.ResultsFBiTE expression did not decrease the infectivity and replication potency of the armed virus. FBiTE-mediated binding of CD3+ effector T cells and FAP+ target cells led to T-cell activation, proliferation, and cytotoxicity of FAP-positive cells in vitro. In vivo, FBiTE expression increased intratumoral accumulation of T cells and decreased the level of FAP, a marker of CAFs, in tumors. The antitumor activity of the FBiTE-armed adenovirus was superior to the parental virus.ConclusionsCombination of viral oncolysis of cancer cells and FBiTE-mediated cytotoxicity of FAP-expressing CAFs might be an effective strategy to overcome a key limitation of oncolytic virotherapy, encouraging its further clinical development.
| S-EPMC6347837 | biostudies-literature
Project description:ObjectiveFibroblast activation protein (FAP) is a serine protease belonging to a S9B prolyl oligopeptidase subfamily. This enzyme has been implicated in cancer development and recently reported to regulate degradation of FGF21, a potent metabolic hormone. Using a known FAP inhibitor, talabostat (TB), we explored the impact of FAP inhibition on metabolic regulation in mice.MethodsTo address this question we evaluated the pharmacology of TB in various mouse models including those deficient in FGF21, GLP1 and GIP signaling. We also studied the ability of FAP to process FGF21 in vitro and TB to block FAP enzymatic activity.ResultsTB administration to diet-induced obese (DIO) animals led to profound decreases in body weight, reduced food consumption and adiposity, increased energy expenditure, improved glucose tolerance and insulin sensitivity, and lowered cholesterol levels. Total and intact plasma FGF21 were observed to be elevated in TB-treated DIO mice but not lean animals where the metabolic impact of TB was significantly attenuated. Furthermore, and in stark contrast to naïve DIO mice, the administration of TB to obese FGF21 knockout animals demonstrated no appreciable effect on body weight or any other measures of metabolism. In support of these results we observed no enzymatic degradation of human FGF21 at either end of the protein when FAP was inhibited in vitro by TB.ConclusionsWe conclude that pharmacological inhibition of FAP enhances levels of FGF21 in obese mice to provide robust metabolic benefits not observed in lean animals, thus validating this enzyme as a novel drug target for the treatment of obesity and diabetes.
| S-EPMC5034526 | biostudies-literature
Project description:Fibroblast Activation Protein (FAP) is a membrane-bound serine protease whose expression is often elevated in activated fibroblasts associated with tissue remodeling in various common diseases such as cancer, arthritis and fibrosis. Like the closely related dipeptidyl peptidase DPPIV, the extracellular domain of FAP can be released into circulation as a functional enzyme, and limited studies suggest that the circulating level of FAP correlates with the degree of tissue fibrosis. Here we describe a novel homogeneous fluorescence intensity assay for circulating FAP activity based on a recently identified natural substrate, FGF21. This assay is unique in that it can effectively distinguish endopeptidase activity of FAP from that of other related enzymes such as prolyl endopeptidase (PREP) and was validated using Fap-deficient mice. Structural modeling was used to elucidate the mechanistic basis for the observed specificity in substrate recognition by FAP, but not by DPPIV or PREP. Finally, the assay was used to detect elevated FAP activity in human patients diagnosed with liver cirrhosis and to determine the effectiveness of a chemical inhibitor for FAP in mice. We propose that the assay presented here could thus be utilized for diagnosis of FAP-related pathologies and for the therapeutic development of FAP inhibitors.
| S-EPMC5624913 | biostudies-literature
Project description:Cancer-associated fibroblasts constitute a vital subpopulation of the tumor stroma and are present in more than 90% of epithelial carcinomas. The overexpression of the serine protease fibroblast activation protein (FAP) allows a selective targeting of a variety of tumors by inhibitor-based radiopharmaceuticals (FAPIs). Of these compounds, FAPI-04 has been recently introduced as a theranostic radiotracer and demonstrated high uptake into different FAP-positive tumors in cancer patients. To enable the delivery of higher doses, thereby improving the outcome of a therapeutic application, several FAPI variants were designed to further increase tumor uptake and retention of these tracers. Methods: Novel quinoline-based radiotracers were synthesized by organic chemistry and evaluated in radioligand binding assays using FAP-expressing HT-1080 cells. Depending on their in vitro performance, small-animal PET imaging and biodistribution studies were performed on HT-1080-FAP tumor-bearing mice. The most promising compounds were used for clinical PET imaging in 8 cancer patients. Results: Compared with FAPI-04, 11 of 15 FAPI derivatives showed improved FAP binding in vitro. Of these, 7 compounds demonstrated increased tumor uptake in tumor-bearing mice. Moreover, tumor-to-normal-organ ratios were improved for most of the compounds, resulting in images with higher contrast. Notably two of the radiotracers, FAPI-21 and -46, displayed substantially improved ratios of tumor to blood, liver, muscle, and intestinal uptake. A first diagnostic application in cancer patients revealed high intratumoral uptake of both radiotracers already 10 min after administration but a higher uptake in oral mucosa, salivary glands, and thyroid for FAPI-21. Conclusion: Chemical modification of the FAPI framework enabled enhanced FAP binding and improved pharmacokinetics in most of the derivatives, resulting in high-contrast images. Moreover, higher doses of radioactivity can be delivered while minimizing damage to healthy tissue, which may improve therapeutic outcome.
| S-EPMC6785792 | biostudies-literature
Project description:Fibroblast activation protein (FAP) is a proline-selective serine protease. It is hardly expressed in healthy adult tissue but upregulated in tissue remodeling sites associated with several diseases including epithelial cancer types, atherosclerosis, arthritis and fibrosis. Ongoing research aims at clinical implementation of FAP as a biomarker for these diseases. Several immunochemical methods that quantify FAP expression have been reported. An alternative/complementary approach focuses on quantification of FAP's enzymatic activity. Developing an activity-based assay for FAP has nonetheless proven challenging because of selectivity issues with respect to prolyl oligopeptidase (PREP). Here, we present substrate-type FAP probes that are structurally derived from a FAP-inhibitor (UAMC1110) that we published earlier. Both cleavage efficiency and FAP-selectivity of the best compounds in the series equal or surpass the most advanced peptide-based FAP substrates reported to date. Finally, proof-of-concept is provided that 4-aminonaphthol containing probes can spatially localize FAP activity in biological samples.
| S-EPMC6691567 | biostudies-literature
Project description:ObjectivesTargeted immunotherapies such as chimeric antigen receptor (CAR)-T cells are emerging as attractive treatment options for glioblastoma, but rely on identification of a suitable tumor antigen. We validated a new target antigen for glioblastoma, fibroblast activation protein (FAP), by undertaking a detailed expression study of human samples.MethodsGlioblastoma and normal tissues were assessed using immunostaining, supported by analyses of published transcriptomic datasets. Short-term cultures of glioma neural stem (GNS) cells were compared to cultures of healthy astrocytes and neurons using flow cytometry. Glioblastoma tissues were dissociated and analysed by high-parameter flow cytometry and single-cell transcriptomics (scRNAseq).ResultsCompared to normal brain, FAP was overexpressed at the gene and protein level in a large percentage of glioblastoma tissues, with highest levels of expression associated with poorer prognosis. FAP was also overexpressed in several paediatric brain cancers. FAP was commonly expressed by cultured GNS cells but absent from normal neurons and astrocytes. Within glioblastoma tissues, the strongest expression of FAP was around blood vessels. In fact, almost every tumor vessel was highlighted by FAP expression, whereas normal tissue vessels and cultured endothelial cells (ECs) lacked expression. Single-cell analyses of dissociated tumors facilitated a detailed characterisation of the main cellular components of the glioblastoma microenvironment and revealed that vessel-localised FAP is because of expression on both ECs and pericytes.ConclusionFibroblast activation protein is expressed by multiple cell types within glioblastoma, highlighting it as an ideal immunotherapy antigen to target destruction of both tumor cells and their supporting vascular network.
| S-EPMC7557106 | biostudies-literature