Fibroblast activation protein in osteosarcoma cells promotes angiogenesis via AKT and ERK signaling pathways

The Role and Application of Fibroblast Activating Protein

Fibroblast activation protein-α (FAP), a type-II transmembrane serine protease, is rarely expressed in normal tissues but highly abundant in pathological diseases, including fibrosis, arthritis, and cancer. Ever since its discovery, we have deciphered its structure and biological properties and continue to investigate its roles in various diseases while attempting to utilize it for targeted therapy. To date, no significant breakthroughs have been made in terms of efficacy. However, in recent years, several practical applications in the realm of imaging diagnosis have been discovered. Given its unique expression in a diverse array of pathological tissues, the fundamental biological characteristics of FAP render it a crucial target for disease diagnosis and immunotherapy. To obtain a more comprehensive understanding of the research progress of FAP, its biological characteristics, involvement in diseases, and recent targeted application research have been reviewed. Moreover, we explored its development trend in the direction of clinical diagnoses and treatment.

Targeting fibroblast activation protein (FAP): advances in CAR-T cell, antibody, and vaccine in cancer immunotherapy

Fibroblast activation protein (FAP) is a serine protease with dual enzymatic activities overexpressed in cancer-associated fibroblasts (CAFs) in several tumor types, while its expression in healthy adult tissues is scarce. FAP overexpression on CAFs is associated with poor prognosis and plays an important role in tumor development, progression, and invasion. Therefore, FAP is considered a robust therapeutic target for cancer therapy. Here, we try to review and highlight the recent advances in immunotherapies for FAP targeting including the anti-FAP antibodies and immunoconjugates, FAP chimeric antigen receptor (CAR)-T cell, and various FAP vaccines in a preclinical and clinical setting. Subsequently, a discussion on the challenges and prospects associated with the development and translation of effective and safe therapies for targeting and depletion of FAP is provided. We proposed that new CAR-T cell engineering strategies and nanotechnology-based systems as well as advanced functional biomaterials can be used to improve the efficiency and safety of CAR-T cells and vaccines against FAP for more personalized immunotherapy. This review emphasizes the immune targeting of FAP as an emerging stromal candidate and one of the crucial elements in immunotherapy and shows the potential for improvement of current cancer therapy. A summary of different immunotherapy approaches to target fibroblast activation protein (FAP) for cancer therapy.

The Prognostic and therapeutic value and clinical implications of fibroblast activation protein-α as a novel biomarker in colorectal cancer

The identification of contributing factors leading to the development of Colorectal Cancer (CRC), as the third fatal malignancy, is crucial. Today, the tumor microenvironment has been shown to play a key role in CRC progression. Fibroblast-Activation Protein-α (FAP) is a type II transmembrane cell surface proteinase expressed on the surface of cancer-associated fibroblasts in tumor stroma. As an enzyme, FAP has di- and endoprolylpeptidase, endoprotease, and gelatinase/collagenase activities in the Tumor Microenvironment (TME). According to recent reports, FAP overexpression in CRC contributes to adverse clinical outcomes such as increased lymph node metastasis, tumor recurrence, and angiogenesis, as well as decreased overall survival. In this review, studies about the expression level of FAP and its associations with CRC patients' prognosis are reviewed. High expression levels of FAP and its association with clinicopathological factors have made as a potential target. In many studies, FAP has been evaluated as a therapeutic target and diagnostic factor into which the current review tries to provide a comprehensive insight. Video Abstract.

Role and mechanism of fibroblast-activated protein-α expression on the surface of fibroblast-like synoviocytes in rheumatoid arthritis

Fibroblast-activated protein-α (FAP) is a type II integrated serine protease expressed by activated fibroblasts during fibrosis or inflammation. Fibroblast-like synoviocytes (FLSs) in rheumatoid arthritis (RA) synovial sites abundantly and stably overexpress FAP and play important roles in regulating the cellular immune, inflammatory, invasion, migration, proliferation, and angiogenesis responses in the synovial region. Overexpression of FAP is regulated by the initial inflammatory microenvironment of the disease and epigenetic signaling, which promotes RA development by regulating FLSs or affecting the signaling cross-linking FLSs with other cells at the local synovium and inflammatory stimulation. At present, several treatment options targeting FAP are in the process of development. This review discusses the basic features of FAP expressed on the surface of FLSs and its role in RA pathophysiology and advances in targeted therapies.

CT radiomics signature: a potential biomarker for fibroblast activation protein expression in patients with pancreatic ductal adenocarcinoma

PURPOSE

To develop and validate a radiomics model to predict fibroblast activation protein (FAP) expression in patients with pancreatic ductal adenocarcinoma (PDAC).

METHODS

This retrospective study included consecutive 152 patients with PDAC who underwent MDCT scan and surgical resection from January 2017 to December 2017 (training set) and from January 2018 to April 2018 (validation set). In the training set, 1409 portal radiomic features were extracted from each patient's preoperative imaging. Optimal features were selected using the least absolute shrinkage and selection operator (LASSO) logistic regression algorithm, whereupon the extreme gradient boosting (XGBoost) was developed using the radiomics features. The performance of the XGBoost classifier performance was assessed by its calibration, discrimination, and clinical usefulness.

RESULTS

The patients were divided into FAP-low (n = 91; 59.87%) and FAP-high (n = 61; 40.13%) groups according to the optimal FAP cutoff (45.71%). Patients in the FAP-low group showed longer survival. The XGBoost classifier comprised 13 selected radiomics features and showed good discrimination in the training set [area under the curve (AUC), 0.97] and the validation set (AUC, 0.75). It also performed well in the calibration test and decision-curve analysis, demonstrating its potential clinical value.

CONCLUSIONS

The XGBoost classifier based on CT radiomics in the portal venous phase can non-invasively predict FAP expression and may help to improve clinical decision-making in patients with PDAC.

Research Progress on Dipeptidyl Peptidase Family: Structure, Function and Xenobiotic Metabolism

Prolyl-specific peptidases or proteases, including Dipeptidyl Peptidase 2, 4, 6, 8, 9, 10, Fibroblast Activation Protein, prolyl endopeptidase and prolyl carboxypeptidase, belong to the dipeptidyl peptidase family. In human physiology and anatomy, they have homology amino acid sequences, similarities in structure, but play distinct functions and roles. Some of them also play important roles in the metabolism of drugs containing endogenous peptides, xenobiotics containing peptides, and exogenous peptides. The major functions of these peptidases in both the metabolism of human health and bioactive peptides are of significant importance in the development of effective inhibitors to control the metabolism of endogenous bioactive peptides. The structural characteristics, distribution of tissue, endogenous substrates, and biological functions were summarized in this review. Furthermore, the xenobiotics metabolism of the dipeptidyl peptidase family is illustrated. All the evidence and information summarized in this review would be very useful for researchers to extend the understanding of the proteins of these families and offer advice and assistance in physiology and pathology studies.

The prognostic significance of fibroblast activation protein-α in human lung adenocarcinoma

Background

Fibroblast activation protein (FAP) is a type II cell surface-bound integral serine protease, which is an important biomarker of cancer-associated fibroblasts. FAP-α performs several biological activities, including remolding extracellular matrix and acting as an immunosuppressor in the tumor microenvironment. However, the proliferation role of FAP-α in human lung adenocarcinoma has not been fully elucidated.

Methods

The expression of FAP-α in 94-paired human lung adenocarcinoma tissues was identified by immunohistochemistry test. The effect of FAP on cell proliferation was examined by CCK-8 assay. RNA-sequencing and bioinformatics analysis were utilized to investigate the underlying mechanism. Western blot analysis, quantitative polymerase chain reaction (qPCR), and nude mice experiments, were also conducted for further validation.

Results

The proliferation rates of human fibroblast strains FAP-HFF and FAP-BJ, and human lung adenocarcinoma cell line FAP-SPC-A-1 were higher than those of controls. The nude mice experiment also showed that FAP could promote the proliferation of SPC-A-1 cell line in vivo. qPCR and Western blot analysis indicated that CCNB1 was upregulated by the overexpression of FAP in the lung adenocarcinoma cell line. The expression of FAP-α was higher in both the cytoplasm and stroma of lung adenocarcinoma than in adjacent normal tissues. Survival analysis indicated that patients with higher expression of FAP-α in tumor stroma had a poor prognosis (P=0.019). The Cancer Genome Atlas Program (TCGA) data also showed that the expression of FAP within tumor tissues was higher (in both cytoplasm and stroma) compared with that in normal tissues (P<0.05).

Conclusions

Our study indicates that FAP-α could facilitate the proliferation of lung adenocarcinoma cells and can be a prognostic marker in human lung adenocarcinoma.

The role of fibroblast activation protein in progression and development of osteosarcoma cells

To investigate the expression levels of fibroblast activation protein (FAP) in human osteosarcoma tissues and its possible correlations with clinical pathological characteristics of patients with osteosarcoma, and to explore the potential effects of FAP on progression and development of osteosarcoma. Immunohistochemistry (IHC) assay was initially performed to detect the expression levels of FAP in 66 tumor tissues and adjacent non-tumor tissues. Patients were sequentially divided into two groups based on different expression levels of FAP. The correlations between the expression levels of FAP and the clinical pathological characteristics were investigated, and the role of FAP in proliferation, migration, and invasion of osteosarcoma cells was assessed via colony formation, MTT, wound healing, and transwell assays, respectively. The possible effects of FAP on tumor growth and metastasis were evaluated in vivo. We further attempted to reveal the underlying mechanism of FAP involved in tumor growth through bioinformatics and IHC assays. High expression levels of FAP were noted in human osteosarcoma tissues. It also was unveiled that FAP was significantly associated with the tumor size (P = 0.005*) and clinical stage (P = 0.017*). Our data further confirmed that knockdown of FAP remarkably blocked proliferation, migration, and invasion of osteosarcoma cells in vitro, and suppressed tumor growth and metastasis in mice via AKT signaling pathway. The possible role of FAP in progression and development of osteosarcoma could be figured out. Our data may be helpful to develop a novel therapeutic target for the treatment of osteosarcoma.

Understanding and Modeling Metastasis Biology to Improve Therapeutic Strategies for Combating Osteosarcoma Progression

Osteosarcoma is a malignant primary tumor of bone, arising from transformed progenitor cells with osteoblastic differentiation and osteoid production. While categorized as a rare tumor, most patients diagnosed with osteosarcoma are adolescents in their second decade of life and underscores the potential for life changing consequences in this vulnerable population. In the setting of localized disease, conventional treatment for osteosarcoma affords a cure rate approaching 70%; however, survival for patients suffering from metastatic disease remain disappointing with only 20% of individuals being alive past 5 years post-diagnosis. In patients with incurable disease, pulmonary metastases remain the leading cause for osteosarcoma-associated mortality; yet identifying new strategies for combating metastatic progression remains at a scientific and clinical impasse, with no significant advancements for the past four decades. While there is resonating clinical urgency for newer and more effective treatment options for managing osteosarcoma metastases, the discovery of druggable targets and development of innovative therapies for inhibiting metastatic progression will require a deeper and more detailed understanding of osteosarcoma metastasis biology. Toward the goal of illuminating the processes involved in cancer metastasis, a convergent science approach inclusive of diverse disciplines spanning the biology and physical science domains can offer novel and synergistic perspectives, inventive, and sophisticated model systems, and disruptive experimental approaches that can accelerate the discovery and characterization of key processes operative during metastatic progression. Through the lens of trans-disciplinary research, the field of comparative oncology is uniquely positioned to advance new discoveries in metastasis biology toward impactful clinical translation through the inclusion of pet dogs diagnosed with metastatic osteosarcoma. Given the spontaneous course of osteosarcoma development in the context of real-time tumor microenvironmental cues and immune mechanisms, pet dogs are distinctively valuable in translational modeling given their faithful recapitulation of metastatic disease progression as occurs in humans. Pet dogs can be leveraged for the exploration of novel therapies that exploit tumor cell vulnerabilities, perturb local microenvironmental cues, and amplify immunologic recognition. In this capacity, pet dogs can serve as valuable corroborative models for realizing the science and best clinical practices necessary for understanding and combating osteosarcoma metastases.

Rab23 contributes to the progression of colorectal cancer via protein kinase B and extracellular signal-regulated kinase signaling pathways

The role of Ras-related protein Rab23 in tumors has attracted increasing attention in recent years; however, whether it can function as an oncogenic protein remains under debate, and its role in colorectal cancer (CRC) is currently unknown. In the present study, high expression of Rab23 in CRC tissues was confirmed using immunohistochemistry, and high expression of Rab23 in CRC cells (SW1116 and HT29) was confirmed using reverse transcription-polymerase chain reaction and western blot analysis. A positive association of Rab23 with tumor size and advanced clinical stage was confirmed by χ² analysis. In addition, the positive association of Rab23 with poor disease-free survival was confirmed by survival analysis. Cell experiments further demonstrated that overexpression of Rab23 increased the expression of the proliferation marker Ki-67 and the proliferative ability in SW1116 and HT29 cells. Molecular mechanism research revealed that the extracellular signal-regulated kinase (ERK) and protein kinase B (AKT) signaling pathways contributed to the high expression of Ki-67 and increased the proliferative ability induced by Rab23 in CRC cells. In conclusion, the study confirmed the high expression of Rab23 in CRC, and its positive association with CRC progression and poor prognosis. Furthermore, the data demonstrated that Rab23 increased the proliferation of CRC cells via the ERK and AKT signaling pathways. These results suggest that Rab23 may be used as a protein for diagnosis and prognosis prediction in patients with CRC, and is proposed to be a novel therapeutic target for improving the patient outcome.