Anti-cancer effect of targeting fibroblast activation protein alpha in glioblastoma through remodeling macrophage phenotype and suppressing tumor progression

Based on small molecules: development and application of fibroblast activation protein inhibitors radiopharmaceutical in tumor precision therapy

The discovery of biomarkers for malignant tumors is driving the development of new radiopharmaceuticals in nuclear medicine. The development and optimization of novel radiopharmaceuticals to occupy an increasingly important role in tumor diagnosis and treatment. In recent years, fibroblast activation protein (FAP) has gained attention as a promising tumor target due to its widespread expression across various tumors. FAP inhibitor (FAPI) radiopharmaceuticals are considered to be the most promising to be developed for targeting FAP due to their rapid and specific tumor targeting. This review briefly outlines the developmental history of FAP-targeted small-molecule enzyme activity inhibitors, highlighting the effective role of targeting molecules, linkers, and certain functional groups in the delivery of radioisotopes to cancerous tissues. These development strategies will serve as a reference for the further development and application of relevant radiopharmaceuticals. This review also delineates the progress on clinical FAPI as a radioisotope delivery vehicle for the targeted radioligand therapy of tumors and introduces the latest combination therapy involving FAPI radiopharmaceutical for tumor treatment. The findings provide novel therapeutic insights into the targeted radioligand therapy of tumors.

68Ga-FAPI-46 PET/CT in the evaluation of gliomas: comparison with 18F-FDG PET/CT and contrast-enhanced MRI

Rationale: This study compared 68Ga-FAPI-46 PET/CT, 18F-fluorodeoxyglucose (FDG) PET/CT, and contrast-enhanced MRI (CE-MRI) for glioma imaging, classification, and recurrence detection and explored PET parameters and molecular pathological profiles. Methods: Between June 2020 and June 2024, we prospectively enrolled patients with space-occupying lesions in the brain or previously treated gliomas. All patients underwent sequential CE-MRI, 68Ga-FAPI-46, and 18F-FDG PET/CT. Diagnostic accuracy was assessed based on a reference standard, and PET parameters were analysed for correlations with WHO grading and molecular characteristics. Results: Forty-eight patients (median age, 51 years; 32 men) with 40 confirmed gliomas were enrolled. For primary tumour diagnosis, the sensitivity of 68Ga-FAPI-46 PET/CT was equivalent to CE-MRI (95% vs. 100%, P = 0.99) and 18F-FDG PET/CT (95% vs. 77%, P = 0.13). 68Ga-FAPI-46 uptake was higher in grade IV than in grade I-II gliomas (5.03 vs. 1.14, P = 0.02). 68Ga-FAPI-46 PET/CT showed significantly higher maximum standardized uptake value and tumour-to-background ratio (TBR) in recurrent tumours than in treatment-related changes and demonstrated favourable sensitivity and specificity for detecting recurrent gliomas, though not significantly superior to 18F-FDG PET/CT (sensitivity: 100% vs. 85%, P = 0.48; specificity: 100% vs. 80%, P = 0.99) and CE-MRI (sensitivity: 100% vs. 100%, P = NA; specificity: 100% vs. 40%, P = 0.25). Glial fibrillary acidic protein-mutant gliomas exhibited higher 68Ga-FAPI-46 uptake than wild-type gliomas. Conclusion: 68Ga-FAPI-46 PET/CT outperformed 18F-FDG and CE-MRI in diagnosing glioma recurrence, although the results were not statistically significant. For primary glioma diagnosis, 68Ga-FAPI-46 PET/CT, despite having a better TBR, did not surpass 18F-FDG PET/CT and CE-MRI in terms of sensitivity and specificity. However, 68Ga-FAPI-46 PET/CT is superior to 18F-FDG for visualizing and classifying gliomas.

STAT3 phosphorylation inhibitor Bt354 exhibits anti-neoplastic activity in glioblastoma multiforme cells

The high mortality rate of glioblastoma multiforme (GBM), a lethal primary brain tumor, is attributable to postsurgical recurrence. STAT3, an oncogenic protein, is a signal transducer and transcription activator encourages cancer cell migration and proliferation, which results in resistance to therapy. STAT3 inhibition reduces cancer metastasis and improves patient prognosis. Bt354, a small molecule STAT inhibitor, exhibits significant cytotoxic and anti-proliferative activities against certain cancer types. Here, we demonstrated that exposure of GBM cells (U87 MG) to Bt354 had a significant, concentration-dependent growth suppression. Bt354 also induced apoptosis and downregulated the expression of the epithelial-mesenchymal transition genes. Therefore, this study suggests the potential of Bt354 for treating GBM owing to its ability to induce cytotoxicity.

Mechanical stiffness promotes skin fibrosis through FAPα-AKT signaling pathway

BACKGROUND

Myofibroblasts contribute to the excessive production, remodeling and cross-linking of the extracellular matrix that characterizes the progression of skin fibrosis. An important insight into the pathogenesis of tissue fibrosis has been the discovery that increased matrix stiffness during fibrosis progression is involved in myofibroblast activation. However, mechanistic basis for this phenomenon remains elusive.

OBJECTIVE

To explore the role of fibroblast activation protein-α (FAPα) in mechanical stiffness-induced skin fibrosis progression.

METHODS

RNA-seq was performed to compare differential genes of mouse dermal fibroblasts (MDFs) grown on low or high stiffness plates. This process identified FAPα, which is a membrane protein usually overexpressed in activated fibroblasts, as a suitable candidate. In vitro assay, we investigate the role of FAPα in mechanical stiffness-induced MDFs activation and downstream pathway. By establishing mouse skin fibrosis model and intradermally administrating FAPα adeno-associated virus (AAV) or a selective Fap inhibitor FAPi, we explore the role of FAPα in skin fibrosis in vivo.

RESULTS

We show that FAPα, a membrane protein highly expressed in myofibroblasts of skin fibrotic tissues, is regulated by increased matrix stiffness. Genetic deletion or pharmacological inhibition of FAPα significantly inhibits mechanical stiffness-induced activation of myofibroblasts in vitro. Mechanistically, FAPα promotes myofibroblast activation by stimulating the PI3K-Akt pathway. Furthermore, we showed that administration of the inhibitor FAPi or FAPα targeted knockdown ameliorated the progression of skin fibrosis.

CONCLUSION

Taken together, we identify FAPα as an important driver of mechanical stiffness-induced skin fibrosis and a potential therapeutic target for the treatment of skin fibrosis.

Tracking tumor alteration in glioma through serum fibroblast activation protein combined with image

PURPOSE

Detecting tumor progression of glioma continues to pose a formidable challenge. The role of fibroblast activation protein (FAP) in gliomas has been demonstrated to facilitate tumor progression. Glioma-circulating biomarkers have not yet been used in clinical practice. This study seeks to evaluate the feasibility of glioma detection through the utilization of a serum FAP marker.

METHODS

We adopted enzyme-linked immunosorbent assay (ELISA) technique to quantify the relative FAP level of serum autoantibodies in a cohort of 87 gliomas. The correlation between preoperative serum autoantibody relative FAP levels and postoperative pathology, including molecular pathology was investigated. A series of FAP tests were conducted on 33 cases of malignant gliomas in order to ascertain their efficacy in monitoring the progression of the disease in relation to imaging observations. To validate the presence of FAP expression in tumors, immunohistochemistry was conducted on four gliomas employing a FAP-specific antibody. Additionally, the investigation encompassed the correlation between postoperative tumor burden, as assessed through volumetric analysis, and the relative FAP level of serum autoantibodies.

RESULTS

A considerable proportion of gliomas exhibited a significantly increased level of serum autoantibody relative FAP level. This elevation was closely associated with both histopathology and molecular pathology, and demonstrated longitudinal fluctuations and variations corresponding to the progression of the disease The correlation between the rise in serum autoantibody relative FAP level and tumor progression and/or exacerbation of symptoms was observed.

CONCLUSIONS

The measurement of serum autoantibody relative FAP level can be used to detect the disease as a valuable biomarker. The combined utilization of its detection alongside MR imaging has the potential to facilitate a more accurate and prompt diagnosis.