Fibroblast activation protein regulates tumor-associated fibroblasts and epithelial ovarian cancer cells

Nanofabrications of Erythrocyte Membrane-Coated Telmisartan Delivery System Effective for Radiosensitivity of Tumor Cells in Mice Model

Background

Radiation stimulates the secretion of tumor stroma and induces resistance, recurrence, and metastasis of stromal-vascular tumors during radiotherapy. The proliferation and activation of tumor-associated fibroblasts (TAFs) are important reasons for the production of tumor stroma. Telmisartan (Tel) can inhibit the proliferation and activation of TAFs (resting TAFs), which may promote radiosensitization. However, Tel has a poor water solubility.

Methods

In this study, self-assembled telmisartan nanoparticles (Tel NPs) were prepared by aqueous solvent diffusion method to solve the insoluble problem of Tel and achieve high drug loading of Tel. Then, erythrocyte membrane (ECM) obtained by hypotonic lysis was coated on the surface of Tel NPs (ECM/Tel) for the achievement of in vivo long circulation and tumor targeting. Immunofluorescence staining, western blot and other biological techniques were used to investigate the effect of ECM/Tel on TAFs activation inhibition (resting effect) and mechanisms involved. The multicellular spheroids (MCSs) model and mouse breast cancer cells (4T1) were constructed to investigate the effect of ECM/Tel on reducing stroma secretion, alleviating hypoxia, and the corresponding promoting radiosensitization effect in vitro. A mouse orthotopic 4T1 breast cancer model was constructed to investigate the radiosensitizing effect of ECM/Tel on inhibiting breast cancer growth and lung metastasis of breast cancer.

Results

ECM/Tel showed good physiological stability and tumor-targeting ability. ECM/Tel could rest TAFs and reduce stroma secretion, alleviate hypoxia, and enhance penetration in tumor microenvironment. In addition, ECM/Tel arrested the cell cycle of 4T1 cells to the radiosensitive G2/M phase. In mouse orthotopic 4T1 breast cancer model, ECM/Tel played a superior role in radiosensitization and significantly inhibited lung metastasis of breast cancer.

Conclusion

ECM/Tel showed synergistical radiosensitization effect on both the tumor microenvironment and tumor cells, which is a promising radiosensitizer in the radiotherapy of stroma-vascular tumors.

Fibroblast activation protein: Pivoting cancer/chemotherapeutic insight towards heart failure

An important mechanism for cancer progression is degradation of the extracellular matrix (ECM) which is accompanied by the emergence and proliferation of an activated fibroblast, termed the cancer associated fibroblast (CAF). More specifically, an enzyme pathway identified to be amplified with local cancer progression and proliferation of the CAF, is fibroblast activation protein (FAP). The development and progression of heart failure (HF) irrespective of the etiology is associated with left ventricular (LV) remodeling and changes in ECM structure and function. As with cancer, HF progression is associated with a change in LV myocardial fibroblast growth and function, and expresses a protein signature not dissimilar to the CAF. The overall goal of this review is to put forward the postulate that scientific discoveries regarding FAP in cancer as well as the development of specific chemotherapeutics could be pivoted to target the emergence of FAP in the activated fibroblast subtype and thus hold translationally relevant diagnostic and therapeutic targets in HF.

Targeting the immune microenvironment for ovarian cancer therapy

Ovarian cancer (OC) is an aggressive malignancy characterized by a complex immunosuppressive tumor microenvironment (TME). Immune checkpoint inhibitors have emerged as a breakthrough in cancer therapy by reactivating the antitumor immune response suppressed by tumor cells. However, in the case of OC, these inhibitors have failed to demonstrate significant improvements in patient outcomes, and existing biomarkers have not yet identified promising subgroups. Consequently, there remains a pressing need to understand the interplay between OC tumor cells and their surrounding microenvironment to develop effective immunotherapeutic approaches. This review aims to provide an overview of the OC TME and explore its potential as a therapeutic strategy. Tumor-infiltrating lymphocytes (TILs) are major actors in OC TME. Evidence has been accumulating regarding the spontaneous TILS response against OC antigens. Activated T-helpers secrete a wide range of inflammatory cytokines with a supportive action on cytotoxic T-cells. Simultaneously, mature B-cells are recruited and play a significant antitumor role through opsonization of target antigens and T-cell recruitment. Macrophages also form an important subset of innate immunity (M1-macrophages) while participating in the immune-stimulation context. Finally, OC has shown to engage a significant natural-killer-cells immune response, exerting direct cytotoxicity without prior sensitization. Despite this initial cytotoxicity, OC cells develop various strategies to induce an immune-tolerant state. To this end, multiple immunosuppressive molecules are secreted to impair cytotoxic cells, recruit regulatory cells, alter antigen presentation, and effectively evade immune response. Consequently, OC TME is predominantly infiltrated by immunosuppressive cells such as FOXP3+ regulatory T-cells, M2-polarized macrophages and myeloid-derived suppressor cells. Despite this strong immunosuppressive state, PD-1/PD-L1 inhibitors have failed to improve outcomes. Beyond PD-1/PD-L1, OC expresses multiple other immune checkpoints that contribute to immune evasion, and each representing potential immune targets. Novel immunotherapies are attempting to overcome the immunosuppressive state and induce specific immune responses using antibodies adoptive cell therapy or vaccines. Overall, the OC TME presents both opportunities and obstacles. Immunotherapeutic approaches continue to show promise, and next-generation inhibitors offer exciting opportunities. However, tailoring therapies to individual immune characteristics will be critical for the success of these treatments.

Remodeling tumor immunosuppression with molecularly imprinted nanoparticles to enhance immunogenic cell death for cancer immunotherapy

Insufficient tumor accumulation and distribution of immunogenic cell death (ICD) inducer as well as low antitumor immunity severely restrict the therapeutic efficacy of tumor immunotherapy. Tumor associated fibroblasts (TAFs) are important in tumor extracellular matrix (ECM) remodeling and immune evasion. Reprogramming tumor immunosuppressive microenvironment via TAFs regulation might present a promising way for enhanced ICD effect and complete tumor elimination. In this study, TAFs derived tryptase imprinted nanoparticles (DMSN@MIPs) are developed to modulate TAFs and improve tumor immunotherapy effect of doxorubicin liposomes (DOX/LIP). Tryptase (TPS), secreted by mast cells, are found to support tumor growth via transcriptionally activating TAFs to an activated state with increased expression of fibroblast activation marker α-smooth muscle actin (α-SMA). DMSN@MIPs canbe used as artificial antibodies, which effectively neutralize TPS, reduce TAFs activation, promote intra-tumor penetration of DOX/LIP and enhance ICD effect induced by DOX/LIP. In addition, the combined administration system remodels immunosuppressive microenvironment, which not only significantly up-regulates immune cells (DC cells, CD8+T cells, NK cells), but also significantly down-regulates immunosuppressive cells (Treg cells, MDSCs cells). Our results support the DMSN@MIPs canbe a promising approach to improve ICD efficacy in cancer immunotherapy.

Current Status of Fibroblast Activation Protein Imaging in Gynecologic Malignancy and Breast Cancer

68Ga-FAPI-PET/computed tomography (CT) is a novel PET/CT radiotracer particularly developed for oncologic imaging. Gynecologic malignancies comprise a broad spectrum of entities and, along with breast cancer, constitute cancers occurring exclusively or primarily, respectively, in women. Thus, a tracer designed not only for one but multiple malignancies has theoretic attractions. Even in comparison with 18F-FDG, the current standard oncologic tracer of nuclear medicine, 68Ga-FAPI, has demonstrated advantages in several tumors. As breast cancer, ovarian cancer, and cervical cancer are among the most common tumor types in women and are often accompanied by high morbidity as well as mortality rates, a reliable staging tool is paramount for optimal therapeutic management.

FAPI PET/CT Imaging-An Updated Review

Despite revolutionizing the field of oncological imaging, Positron Emission Tomography (PET) with [¹⁸F]Fluorodeoxyglucose (FDG) as its workhorse is limited by a lack of specificity and low sensitivity in certain tumor subtypes. Fibroblast activation protein (FAP), a type II transmembrane glycoprotein, is expressed by cancer-associated fibroblasts (CAFs) that form a major component of the tumor stroma. FAP holds the promise to be a pan-cancer target, owing to its selective over-expression in a vast majority of neoplasms, particularly epithelial cancers. Several radiolabeled FAP inhibitors (FAPI) have been developed for molecular imaging and potential theranostic applications. Preliminary data on FAPI PET/CT remains encouraging, with extensive multi-disciplinary clinical research currently underway. This review summarizes the existing literature on FAPI PET/CT imaging with an emphasis on diagnostic applications, comparison with FDG, pitfalls, and future directions.

FAP is critical for ovarian cancer cell survival by sustaining NF-κB activation through recruitment of PRKDC in lipid rafts

Fibroblast activation protein (FAP) is tumor-specific and plays an important role in tumorigenecity. However, agents against its enzymatic activity or extracellular presence were unsuccessful in the clinic for undefined reasons. Here we show that FAP expression is higher in advanced ovarian cancer and is only detected in invasive ovarian cancer cells. Silencing FAP induces apoptosis and FAP's enzymatic activity is dispensable for cell survival. To elucidate the cause of apoptosis, we find that NF-κB activity is diminished when FAP is depleted and BIRC5 (survivin) acts downstream of FAP-NF-κB axis to promote cell survival. To uncover the link between FAP and NF-κB activation, we reveal that PRKDC (DNA-PK, DNA-dependent protein kinase) forms complex with FAP and is required for NF-κB activation and cell survival. Remarkably, FAP-PRKDC interaction occurs only in lipid rafts, and depleting FAP prevents lipid raft localization of PRKDC. Given the known ability of PRKDC to direct NF-κB activation, these results suggest that FAP recruits PRKDC in lipid rafts for NF-κB activation. FAP's non-enzymatic role and functioning from lipid rafts for cell survival also offer an explanation on the failure of past FAP-targeted therapies. Finally, we demonstrate that EpCAM aptamer-delivered FAP siRNA impeded intraperitoneal xenograft development of ovary tumors.

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.

Comparison of 68 Ga-FAPI-04 and fluorine-18-fluorodeoxyglucose PET/computed tomography in the detection of ovarian malignancies

BACKGROUND

Currently, fluorine-18-fluorodeoxyglucose ( 18 F-FDG) is the most frequently used diagnostical radiotracer for PET/computed tomography (PET/CT) in ovarian malignancies. However, 18 F-FDG has some limitations. The fibroblast activation protein inhibitor (FAPI) previously demonstrated highly promising results in studies on various tumor entities and 68 Ga-labeled FAPI presents a promising alternative to 18 F-FDG. This study aimed to compare the performance of 68 Ga-FAPI and 18 F-FDG PET/CT for imaging of ovarian malignancies.

METHODS

A total of 27 patients were included in this retrospective study conducted at the Affiliated Hospital of Southwest Medical University between June 2020 and February 2022. The 18 F-FDG and 68 Ga-FAPI uptakes of tumors, lymph nodes, and distant metastases were quantified using the maximum standardized uptake values, and the tumor-to-background ratios were also evaluated and calculated by using the Wilcoxon signed-rank test.

RESULTS

Twenty-one patients with suspected ( n  = 11) and previously treated ovarian malignancies ( n  = 10) were in statistical analysis finally. For detecting tumors, 68 Ga-FAPI PET/CT was more sensitive than 18 F-FDG PET/CT [14 of 14 (100%) vs. 11 of 14 (78%)], lymph node metastases [75 of 75 (100%) vs. 60 of 75 (80%)] and superior to 18 F-FDG PET/CT in terms of the peritoneal and pleural metastases [9 of 9 (100%) vs. 5 of 9 (56%)]. For four of the newly diagnosed patients ( n  = 11), 68 Ga-FAPI PET/CT upstaged the clinical stage compared to 18 F-FDG PET/CT.

CONCLUSION

68 Ga-FAPI PET/CT has superior potential in the detection of ovarian cancers, especially in peritoneal carcinomatosis. 68 Ga-FAPI PET/CT may be a promising supplement for staging and follow-up of ovarian malignancies.

The Superiority of Fibroblast Activation Protein Inhibitor (FAPI) PET/CT Versus FDG PET/CT in the Diagnosis of Various Malignancies

Cancer represents a major cause of death worldwide and is characterized by the uncontrolled proliferation of abnormal cells that escape immune regulation. It is now understood that cancer-associated fibroblasts (CAFs), which express specific fibroblast activation protein (FAP), are critical participants in tumor development and metastasis. Researchers have developed various FAP-targeted probes for imaging of different tumors from antibodies to boronic acid-based inhibitor molecules and determined that quinoline-based FAP inhibitors (FAPIs) are the most appropriate candidate as the radiopharmaceutical for FAPI PET/CT imaging. When applied clinically, FAPI PET/CT yielded satisfactory results. Over the past few years, the utility and effectiveness of tumor detection and staging of FAPI PET/CT have been compared with FDG PET/CT in various aspects, including standardized uptake values (SUVs), rate of absorbance and clearance. This review summarizes the development and clinical application of FAPI PET/CT, emphasizing the diagnosis and management of various tumor types and the future prospects of FAPI imaging.

Functional roles of FAP-α in metabolism, migration and invasion of human cancer cells

Fibroblast activation protein-α (FAP-α) is a transmembrane serine protease that is attracting significant interest as it is expressed by a subgroup of cancer-associated fibroblasts that play a role in immune suppression and cancer metastasis. FAP-α is also expressed by some cancer cells, such as melanoma, colorectal and breast cancer cells. Triple negative breast cancer (TNBC) is an aggressive cancer that urgently requires identification of novel targets for therapy. To expand our understanding of the functional roles of FAP-α in TNBC we engineered a human TNBC cell line, MDA-MB-231, to stably overexpress FAP-α and characterized changes in metabolism by ¹H magnetic resonance spectroscopy, cell proliferation, migration characterized by wound healing, and invasion. FAP-α overexpression resulted in significant alterations in myoinositol, choline metabolites, creatine, and taurine, as well as a significant increase of migration and invasion, although proliferation remained unaltered. The increase of migration and invasion are consistent with the known activities of FAP-α as an exopeptidase and endopeptidase/gelatinase/collagenase in tissue remodeling and repair, and in cell migration. We additionally determined the effects of FAP-α overexpression on the human fibrosarcoma HT1080 cell line that showed increased migration, accompanied by limited changes in metabolism that identified the dependency of the metabolic changes on cell type. These metabolic data identify a previously unknown role of FAP-α in modifying cancer cell metabolism in the TNBC cell line studied here that may provide new insights into its functional roles in cancer progression.

Advancement and Future Perspective of FAPI PET/CT In Gynecological Malignancies

Fibroblast activation protein (FAP) is ubiquitously present in healthy tissue, and additionally upregulated by cancer associated fibroblasts (CAFs) leading to high levels of FAP. Thus, neoplastic tissue, which is containing CAFs, characterized by a high presence of FAP. Moreover, in more than 90% of all epithelial tumors this phenomenon seems to occur, including many gynecological tumors, providing the foundation for a successful application of FAP-ligands. However, FAP upregulation, can also be initiated by benign conditions such as inflammation, hormonal-influence, and wound healing. Gynecological cancers seem to represent a field of interest for the utilization of FAPI-PET/CT to potentially improve staging, restaging and therapeutic management. First highly promising investigations demand further research in order to validate these preliminary findings.

The Role of Cancer-Associated Fibroblasts in Ovarian Cancer

Simple Summary

Ovarian cancer is a lethal gynecologic tumor and is generally resistant to conventional treatments. Stable cancer-associated fibroblasts (CAFs) are important cellular components in the ovarian cancer tumor microenvironment and may provide novel resources for future treatment strategies. Different subtypes of CAFs display specific functions in tumor pathogenesis and various CAF markers suggest potential treatment targets. Several clinical or preclinical trials have targeted stromal fibroblasts and focused on the properties of CAFs to enhance ovarian cancer treatment efficacy. This review concentrates on the origins, subtypes, and activation of CAFs, as well as specific roles of CAFs in regulating tumor development and drug resistance, and aims to provide potential and prospective targets for improving the therapeutic efficacy of ovarian cancer treatment.

Abstract

Ovarian cancer is a lethal gynecologic tumor and is generally resistant to conventional treatments. Stable cancer-associated fibroblasts (CAFs) are important cellular components in the ovarian cancer tumor microenvironment and may provide novel resources for future treatment strategies. Different subtypes of CAFs display specific functions in tumor pathogenesis and various CAF markers suggest potential treatment targets, such as FAP and GPR77. Both autocrine and paracrine cytokines play important roles in the CAF activation process and regulate tumor progression. Downstream mediators and pathways, including IL-6, TGF-β, NF-κB, mitogen-activated protein kinase (MAPK), and AKT/mTOR/(p70S6K), play important roles in the initiation, proliferation, invasiveness, and metastasis of ovarian cancer cells and also participate in angiogenesis, therapeutic resistance, and other biological processes. Several clinical or preclinical trials have targeted stromal fibroblasts and focused on the properties of CAFs to enhance ovarian cancer treatment outcomes. This review concentrates on the origins, subtypes, and activation of CAFs, as well as specific roles of CAFs in regulating tumor development and drug resistance, and aims to provide potential and prospective targets for improving the therapeutic efficacy of ovarian cancer treatment.

Higher accuracy of [68 Ga]Ga-DOTA-FAPI-04 PET/CT comparing with 2-[18F]FDG PET/CT in clinical staging of NSCLC

PURPOSE

This study aimed to explore the clinical staging performance of [⁶⁸ Ga]Ga-DOTA-FAPI-04 PET/CT compared with that of 2-[¹⁸F]FDG PET/CT in non-small cell lung cancer (NSCLC) patients lesion by lesion.

METHODS

A total of 134 diagnosed or suspected NSCLC patients were enrolled in the prospective study (ChiCTR2000038080); they received paired 2-[¹⁸F]FDG PET/CT and [⁶⁸ Ga]Ga-DOTA-FAPI-04 PET/CT. Of these patients, the retrospective analysis of 74 NSCLC patients with pathological results was conducted from primary tumor (T) diagnosis, lymph node (N), and metastatic lesion (M) staging. The imaging characteristics of the lung nodules and suspected metastases were obtained and analyzed, and the staging performance of 2-[¹⁸F]FDG PET/CT and [⁶⁸ Ga]Ga-DOTA-FAPI-04 PET/CT was compared.

RESULTS

For T diagnosis, [⁶⁸ Ga]Ga-DOTA-FAPI-04 showed better diagnostic performance than 2-[¹⁸F]FDG in 79 lung nodules of 72 patients, especially for nonsolid and small-dimension adenocarcinoma nodules. For N staging, 98 lymph nodes (LNs) with pathological results in 37 patients were analyzed. The SUV_max of [⁶⁸ Ga]Ga-DOTA-FAPI-04 in the nonmetastatic LNs was significantly lower than that in the metastatic LNs. Regarding metastatic LN identification, the calculated optimum cut-off value of [⁶⁸ Ga]Ga-DOTA-FAPI-04 SUV_max was 5.5, and the diagnostic accuracy using [⁶⁸ Ga]Ga-DOTA-FAPI-04 and 2-[¹⁸F]FDG criteria was 94% and 30%, respectively (P < 0.001). For M staging, [⁶⁸ Ga]Ga-DOTA-FAPI-04 identified more lesions than 2-[¹⁸F]FDG (257 vs. 139 lesions) in 14 patients with multiple metastases. Overall, the staging accuracy of [⁶⁸ Ga]Ga-DOTA-FAPI-04 was better than that of 2-[¹⁸F]FDG in 52 patients with different pathological stages [43/52 (82.7%) vs. 27/52 (51.9%), P = 0.001].

CONCLUSION

Compared with 2-[¹⁸F]FDG PET/CT, [⁶⁸ Ga]Ga-DOTA-FAPI-04 PET/CT demonstrated better staging performance in NSCLC patients with different pathological stages, especially those with localized disease.

GLIS1 in Cancer-Associated Fibroblasts Regulates the Migration and Invasion of Ovarian Cancer Cells

A cancer-associated fibroblasts (CAFs) are the most important players that modulate tumor aggressiveness. In this study, we aimed to identify CAF-related genes in ovarian serous carcinomas (OSC) that account for the high incidence and mortality of ovarian cancers (OCs) and to develop therapeutic targets for tumor microenvironment modulation. Here, we performed a microarray analysis of CAFs isolated from three metastatic and three nonmetastatic OSC tissues and compared their gene expression profiles. Among the genes increased in metastatic CAFs (mCAFs), GLIS1 (Glis Family Zinc Finger 1) showed a significant increase in both the gene mRNA and protein expression levels. Knockdown of GLIS1 in mCAFs significantly inhibited migration, invasion, and wound healing ability of OC cells. In addition, an in vivo study demonstrated that knockdown of GLIS1 in CAFs reduced peritoneal metastasis. Taken together, these results suggest that CAFs support migration and metastasis of OC cells by GLIS1 overexpression. It also indicates GLIS1 in CAFs might be a potential therapeutic target to inhibit OC metastasis.

Utilizing digital pathology to quantify stromal caveolin-1 expression in malignant and benign ovarian tumors: Associations with clinicopathological parameters and clinical outcomes

Loss of stromal caveolin-1 (Cav-1) is a biomarker of a cancer-associated fibroblast (CAF) phenotype and is related to progression, metastasis, and poor outcomes in several cancers. The objective of this study was to evaluate the clinical significance of Cav-1 expression in invasive epithelial ovarian cancer (OvCa). Epithelial and stromal Cav-1 expression were quantified in serous OvCa and benign ovarian tissue in two, independent cohorts–one quantified expression using immunohistochemistry (IHC) and the other using multiplex immunofluorescence (IF) with digital image analysis designed to target CAF-specific expression. Cav-1 expression was significantly downregulated in OvCa stroma compared to non-neoplastic stroma using both the IHC (p = 0.002) and IF (p = 1.8x10^-13) assays. OvCa stroma showed Cav-1 downregulation compared to tumor epithelium with IHC (p = 1.2x10^-24). Conversely, Cav-1 expression was higher in OvCa stroma compared to tumor epithelium with IF (p = 0.002). There was moderate correlation between IHC and IF methods for stromal Cav-1 expression (r² = 0.69, p = 0.006) whereas there was no correlation for epithelial expression (r² = 0.006, p = 0.98). Irrespective of the staining assay, neither response to therapy or overall survival correlated with the expression level of Cav-1 in the stroma or tumor epithelium. Our findings demonstrate a loss of stromal Cav-1 expression in ovarian serous carcinomas. Studies are needed to replicate these findings and explore therapeutic implications, particularly for immunotherapy response.

68Ga-FAPI-PET/CT in patients with various gynecological malignancies

PURPOSE

68Ga-FAPI (fibroblast activation protein inhibitor) is a novel and highly promising radiotracer for PET/CT imaging. The aim of this retrospective analysis is to explore the potential of FAPI-PET/CT in gynecological malignancies. We assessed biodistribution, tumor uptake, and the influence of pre- or postmenopausal status on tracer accumulation in hormone-sensitive organs. Furthermore, a comparison with the current standard oncological tracer 18F-FDG was performed in selected cases.

PATIENTS AND METHODS

A total of 31 patients (median age 59.5) from two centers with several gynecological tumors (breast cancer; ovarian cancer; cervical cancer; endometrial cancer; leiomyosarcoma of the uterus; tubal cancer) underwent 68Ga-FAPI-PET/CT. Out of 31 patients, 10 received an additional 18F-FDG scan within a median time interval of 12.5 days (range 1-76). Tracer uptake was quantified by standardized uptake values (SUV)max and (SUV)mean, and tumor-to-background ratio (TBR) was calculated (SUVmax tumor/ SUVmean organ). Moreover, a second cohort of 167 female patients with different malignancies was analyzed regarding their FAPI uptake in normal hormone-responsive organs: endometrium (n = 128), ovary (n = 64), and breast (n = 147). These patients were categorized by age as premenopausal (<35 years; n = 12), postmenopausal (>65 years; n = 68), and unknown menstrual status (35-65 years; n = 87), followed by an analysis of FAPI uptake of the pre- and postmenopausal group.

RESULTS

In 8 out of 31 patients, the primary tumor was present, and all 31 patients showed lesions suspicious for metastasis (n = 81) demonstrating a high mean SUVmax in both the primary (SUVmax 11.6) and metastatic lesions (SUVmax 9.7). TBR was significantly higher in 68Ga-FAPI compared to 18F-FDG for distant metastases (13.0 vs. 5.7; p = 0.047) and by trend for regional lymph node metastases (31.9 vs 27.3; p = 0.6). Biodistribution of 68Ga-FAPI-PET/CT presented significantly lower uptake or no significant differences in 15 out of 16 organs, compared to 18F-FDG-PET/CT. The highest uptake of all primary lesions was obtained in endometrial carcinomas (mean SUVmax 18.4), followed by cervical carcinomas (mean SUVmax 15.22). In the second cohort, uptake in premenopausal patients differed significantly from postmenopausal patients in endometrium (11.7 vs 3.9; p < 0.0001) and breast (1.8 vs 1.0; p = 0.004), whereas no significant difference concerning ovaries (2.8 vs 1.6; p = 0.141) was observed.

CONCLUSION

Due to high tracer uptake resulting in sharp contrasts in primary and metastatic lesions and higher TBRs than 18F-FDG-PET/CT, 68Ga-FAPI-PET/CT presents a promising imaging method for staging and follow-up of gynecological tumors. The presence or absence of the menstrual cycle seems to correlate with FAPI accumulation in the normal endometrium and breast. This first investigation of FAP ligands in gynecological tumor entities supports clinical application and further research in this field.

FAP and FAPI-PET/CT in Malignant and Non-Malignant Diseases: A Perfect Symbiosis?

A fibroblast activation protein (FAP) is an atypical type II transmembrane serine protease with both endopeptidase and post-proline dipeptidyl peptidase activity. FAP is overexpressed in cancer-associated fibroblasts (CAFs), which are found in most epithelial tumors. CAFs have been implicated in promoting tumor cell invasion, angiogenesis and growth and their presence correlates with a poor prognosis. However, FAP can generally be found during the remodeling of the extracellular matrix and therefore can be detected in wound healing and benign diseases. For instance, chronic inflammation, arthritis, fibrosis and ischemic heart tissue after a myocardial infarction are FAP-positive diseases. Therefore, quinoline-based FAP inhibitors (FAPIs) bind with a high affinity not only to tumors but also to a variety of benign pathologic processes. When these inhibitors are radiolabeled with positron emitting radioisotopes, they provide new diagnostic and prognostic tools as well as insights into the role of the microenvironment in a disease. In this respect, they deliver additional information beyond what is afforded by conventional FDG PET scans that typically report on glucose uptake. Thus, FAP ligands are considered to be highly promising novel tracers that offer a new diagnostic and theranostic potential in a variety of diseases.

Fibroblast Activation Protein-α as a Target in the Bench-to-Bedside Diagnosis and Treatment of Tumors: A Narrative Review

Fibroblast activation protein-α (FAP) is a type II integral serine protease that is specifically expressed by activated fibroblasts. Cancer-associated fibroblasts (CAFs) in the tumor stroma have an abundant and stable expression of FAP, which plays an important role in promoting tumor growth, invasion, metastasis, and immunosuppression. For example, in females with a high incidence of breast cancer, CAFs account for 50–70% of the cells in the tumor’s microenvironment. CAF overexpression of FAP promotes tumor development and metastasis by influencing extracellular matrix remodeling, intracellular signaling, angiogenesis, epithelial-to-mesenchymal transition, and immunosuppression. This review discusses the basic biological characteristics of FAP and its applications in the diagnosis and treatment of various cancers. We review the emerging basic and clinical research data regarding the use of nanomaterials that target FAP.

TGF-β Signaling: From Tissue Fibrosis to Tumor Microenvironment

Transforming growth factor-β (TGF-β) signaling triggers diverse biological actions in inflammatory diseases. In tissue fibrosis, it acts as a key pathogenic regulator for promoting immunoregulation via controlling the activation, proliferation, and apoptosis of immunocytes. In cancer, it plays a critical role in tumor microenvironment (TME) for accelerating invasion, metastasis, angiogenesis, and immunosuppression. Increasing evidence suggest a pleiotropic nature of TGF-β signaling as a critical pathway for generating fibrotic TME, which contains numerous cancer-associated fibroblasts (CAFs), extracellular matrix proteins, and remodeling enzymes. Its pathogenic roles and working mechanisms in tumorigenesis are still largely unclear. Importantly, recent studies successfully demonstrated the clinical implications of fibrotic TME in cancer. This review systematically summarized the latest updates and discoveries of TGF-β signaling in the fibrotic TME.

Role of cancer-associated fibroblasts in the resistance to antitumor therapy, and their potential therapeutic mechanisms in non-small cell lung cancer

Non-small cell lung cancer (NSCLC) is a malignant tumor with high morbidity and mortality rates, which seriously endangers human health. Although treatment methods continue to evolve, the emergence of drug resistance is inevitable and seriously hinders the treatment of NSCLC. The tumor microenvironment (TME) protects tumor cells from the effects of chemotherapeutic drugs, which can lead to drug resistance. Cancer-associated fibroblasts (CAFs) are an important component of the TME, and various studies have demonstrated that CAFs play a crucial role in drug resistance in NSCLC. However, the drug resistance mechanism of CAFs and whether CAFs can be used as a target to reverse the resistance of tumor cells remain unclear. The present review discusses this issue and describes the heterogeneity of CAF markers, as well as their origins and resident organs, and the role and mechanism of this heterogeneity in NSCLC progression. Furthermore, the mechanism of CAF-mediated NSCLC resistance to chemotherapy, targeted therapy and immunotherapy is introduced, and strategies to reverse this resistance are described.

Interleukin‑8 released by cancer‑associated fibroblasts attenuates the autophagy and promotes the migration of ovarian cancer cells

The tumor microenvironment composed of a mixture of stromal cells and their secretions has a marked impact on cancer progression. In particular, soluble factors and metabolites contribute to malignancy through the dysregulation of autophagy in cancer cells. The present study investigated the effects of ovarian cancer‑associated fibroblasts (OVCAFs) with their secretory substances on the autophagy and migration of ovarian cancer cells. The conditioned‑medium (CM) of OVCAFs isolated from fresh human ovarian cancer tissues was analyzed for the levels of 27 common cytokines/chemokines using a cytokine array. Autophagy in cancer cells was assessed by determining the expression of the vacuolar form of LC3 by western blot analysis and immunofluorescence. Cancer cell migration was assessed by Transwell migration assay. Interleukin (IL)‑8 was found to be the most highly upregulated cytokine among the cytokines/chemokines found in the OVCAF‑CM. The role of IL‑8 in ovarian cancer cell migration and its mechanistic link with autophagy was investigated. Recombinant human IL‑8 (rhIL‑8) stimulated the migration of SKOV3 and Kuramochi ovarian cancer cells, and concurrently downregulated basal autophagy, in concentration‑dependent manner. Compared to the CM of control counterpart normal fibroblasts isolated from benign ovaries (OVNF‑CM), the CM from 3 OVCAF isolates (namely, OVCAF‑9, ‑20 and ‑43) exerted effects similar to rhIL‑8 on both cancer cell lines. The pharmacological induction of autophagy with rapamycin or metformin attenuated the pro‑migratory effects of IL‑8. Neutralizing anti‑IL‑8 antibody counteracted the inhibitory effect of OVCAF‑CM on basal autophagy. On the whole, the present study highlights the involvement of IL‑8 released by CAFs in the ovarian tumor microenvironment in promoting cancer cell migration through the suppression of autophagy.

The role of fibroblast activation protein in health and malignancy

Fibroblast activation protein-α (FAP) is a type-II transmembrane serine protease expressed almost exclusively to pathological conditions including fibrosis, arthritis, and cancer. Across most cancer types, elevated FAP is associated with worse clinical outcomes. Despite the clear association between FAP and disease severity, the biological reasons underlying these clinical observations remain unclear. Here we review basic FAP biology and FAP's role in non-oncologic and oncologic disease. We further explore how FAP may worsen clinical outcomes via its effects on extracellular matrix remodeling, intracellular signaling regulation, angiogenesis, epithelial-to-mesenchymal transition, and immunosuppression. Lastly, we discuss the potential to exploit FAP biology to improve clinical outcomes.

Fibroblast Activation Protein-α Expressing Fibroblasts Promote Lymph Node Metastasis in Esophageal Squamous Cell Carcinoma

Background and Objectives

Esophageal squamous cell carcinoma (ESCC) remains one of the most common malignancies in China and has a high metastasis rate and poor prognosis. Fibroblast activation protein-α (FAP-α) is a serine peptidase the expression of which in cancer-associated fibroblasts has been associated with a higher risk of metastases and poor survival. This study aimed to analyze the correlation of FAP-α expression with the lymph node metastasis and prognostic significance in ESCC.

Methods

FAP-α expression was examined in 121 resected ESCC specimens and 10 adjacent normal tissue using immunohistochemistry. FAP-α expression was scored in the stromal fibroblasts adjacent to neoplastic nests. A chi-square test was used to analyze the correlation between FAP-α expression in tumors stromal and lymph node metastasis of ESCC. The association between FAP-α expression and prognosis was evaluated using univariable and multivariable statistical modeling.

Results

FAP-α expression was absent in the benign controls. FAP-α expression was evident in the stromal 37% (45/121) of ESCC. Expression of FAP-α level is significantly associated with lymph node metastasis (p=0.023), but it is not correlated to age, gender, and tumor location in ESCC patients. Stromal FAP-α expression was significantly associated with poor survival in univariable (HR 2.009; 95% CI 1.259–3.205; p=0.003) and multivariable analysis (HR 1.833; 95% CI 1.144–2.937; p=0.012).

Conclusion

FAP-α may be an important regulator in lymph node metastasis of ESCC and may provide a novel therapeutic target in ESCC.

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Antitumor immunity targeting fibroblast activation protein-α in a mouse Lewis lung carcinoma model

The tumor stromal microenvironment is an integral part of the occurrence and development of tumor. Cancer-associated fibroblasts (CAFs) are a key component of most tumor stromal microenvironments. The present study aimed to investigate the use of CAFs-targeted immunotherapy to fibroblast activation protein-α (FAP-α) expressed in CAFs. Recombinant adenoviral vectors containing the mouse FAP-α cDNA (rAd-FAP-α) were constructed. C57BL/6 mice were immunized with rAd-FAP-α infected dendritic cells (DCs) against FAP-α, which is overexpress in CAFs. The results demonstrated that mice vaccinated with rAd-FAP-α DCs gave rise to potent FAP-α-specific cytotoxic T lymphocytes capable of lysing Lewis lung cancer (LLC) CAFs. Furthermore, mice vaccinated with rAd-FAP-α-transduced DCs induced an effective therapeutic or protective antitumor immunity to LLC in a subcutaneous model, and prolonged overall survival time compared with mice vaccinated with the control recombinant adenovirus-transduced DCs (rAd-c DCs) or DCs alone. The results of the present study suggested that FAP-α, which is preferentially expressed in CAFs, may be considered as a potential target for killing or destroying CAFs within the tumor stromal microenvironment, and may be exploited to develop immunogenic tumor vaccines.

Cell type-specific transcriptomics of esophageal adenocarcinoma as a scalable alternative for single cell transcriptomics

Single‐cell transcriptomics have revolutionized our understanding of the cell composition of tumors and allowed us to identify new subtypes of cells. Despite rapid technological advancements, single‐cell analysis remains resource‐intense hampering the scalability that is required to profile a sufficient number of samples for clinical associations. Therefore, more scalable approaches are needed to understand the contribution of individual cell types to the development and treatment response of solid tumors such as esophageal adenocarcinoma where comprehensive genomic studies have only led to a small number of targeted therapies. Due to the limited treatment options and late diagnosis, esophageal adenocarcinoma has a poor prognosis. Understanding the interaction between and dysfunction of individual cell populations provides an opportunity for the development of new interventions. In an attempt to address the technological and clinical needs, we developed a protocol for the separation of esophageal carcinoma tissue into leukocytes (CD45+), epithelial cells (EpCAM+), and fibroblasts (two out of PDGFRα, CD90, anti‐fibroblast) by fluorescence‐activated cell sorting and subsequent RNA sequencing. We confirm successful separation of the three cell populations by mapping their transcriptomic profiles to reference cell lineage expression data. Gene‐level analysis further supports the isolation of individual cell populations with high expression of CD3, CD4, CD8, CD19, and CD20 for leukocytes, CDH1 and MUC1 for epithelial cells, and FAP, SMA, COL1A1, and COL3A1 for fibroblasts. As a proof of concept, we profiled tumor samples of nine patients and explored expression differences in the three cell populations between tumor and normal tissue. Interestingly, we found that angiogenesis‐related genes were upregulated in fibroblasts isolated from tumors compared with normal tissue. Overall, we suggest our protocol as a complementary and more scalable approach compared with single‐cell RNA sequencing to investigate associations between clinical parameters and transcriptomic alterations of specific cell populations in esophageal adenocarcinoma.

The Role of Stroma in Ovarian Cancer

Background: Ovarian cancer is one of the gynecological malignancies responsible for thousands of deaths in women worldwide. Malignant solid tumors are formed by malignant cells and stroma that influence each other, where different types of cells in the stromal environment can be recruited by malignant cells to promote tumor growth and facilitate metastasis. The chronic inflammatory response is increasingly accepted in its relation to the pathophysiology of the onset and development of tumors, sustained cell proliferation in an environment rich in inflammatory cells, growth factors, activated stroma and DNA damage agents may increase the risk to develop a neoplasm.Methods: A search for the following keywords was performed in the PubMed database; "Ovarian cancer", "stroma", "tumor-associated macrophages", "cancer-associated fibroblasts", "cytokines", "angiogenesis", "epithelial-mesenchymal transition", and "extracellular matrix".Results: The articles identified were published in English between 1971 and 2018. A total of 154 articles were selected for further analysis. Conclusion: We consider ovarian cancer as a heterogeneous disease, not only in the sense that different histological or molecular subtypes may be behind the same clinical result, but also that multiple cell types besides cancer cells, like other non-cellular components, need to be mobilized and coordinated to support tumor survival, growth, invasion and progression.

IDH-wildtype glioblastomas and grade III/IV IDH-mutant gliomas show elevated tracer uptake in fibroblast activation protein-specific PET/CT

PURPOSE

Targeting fibroblast activation protein (FAP) is a new diagnostic approach allowing the visualization of tumor stroma. Here, we applied FAP-specific PET imaging to gliomas. We analyzed the target affinity and specificity of two FAP ligands (FAPI-02 and FAPI-04) in vitro, and the pharmacokinetics and biodistribution in mice in vivo. Clinically, we used ⁶⁸Ga-labeled FAPI-02/04 for PET imaging in 18 glioma patients (five IDH-mutant gliomas, 13 IDH-wildtype glioblastomas).

METHODS

For binding studies with ¹⁷⁷Lu-radiolabeled FAPI-02/04, we used the glioblastoma cell line U87MG, FAP-transfected fibrosarcoma cells, and CD26-transfected human embryonic kidney cells. For pharmacokinetic and biodistribution studies, U87MG-xenografted mice were injected with ⁶⁸Ga-labeled compounds followed by small-animal PET imaging and ¹⁷⁷Lu-labeled FAPI-02/04, respectively. Clinical PET/CT scans were performed 30 min post intravenous administration of ⁶⁸Ga-FAPI-02/04. PET and MRI scans were co-registrated. Immunohistochemistry was done on 14 gliomas using a FAP-specific antibody.

RESULTS

FAPI-02 and FAPI-04 showed high binding specificity to FAP. FAPI-04 demonstrated higher tumor accumulation and delayed elimination compared with FAPI-02 in preclinical studies. IDH-wildtype glioblastomas and grade III/IV, but not grade II, IDH-mutant gliomas showed elevated tracer uptake. In glioblastomas, we observed spots with increased uptake in projection on contrast-enhancing areas. Immunohistochemistry showed FAP-positive cells with mainly elongated cell bodies and perivascular FAP-positive cells in glioblastomas and an anaplastic IDH-mutant astrocytoma.

CONCLUSIONS

Using FAP-specific PET imaging, increased tracer uptake in IDH-wildtype glioblastomas and high-grade IDH-mutant astrocytomas, but not in diffuse astrocytomas, may allow non-invasive distinction between low-grade IDH-mutant and high-grade gliomas. Therefore, FAP-specific imaging in gliomas may be useful for follow-up studies although further clinical evaluation is required.

Drug delivery systems targeting tumor-associated fibroblasts for cancer immunotherapy

Solid tumors especially desmoplastic tumors are complex organ-like structures. Tumor-associated fibroblasts (TAFs), one type of the stromal cells, support the initiation, progression, and metastasis of carcinomas. TAFs also contribute to immunosuppressive tumor microenvironment (TME) and hinder T lymphocytes in killing tumors. Here, the role of TAFs in TME is discussed. In specific, TAFs form barriers for the penetration of T lymphocytes. TAFs also act as negative regulators for T lymphocytes. These findings suggest that targeting TAFs is a promising strategy for improving cancer immunotherapy. Our previous studies have indicated the ability of therapeutic nanoparticles to distribute into, and deplete or inactivate TAFs. This approach is discussed in the context of developing specific and effective immunotherapies for cancer.

Cancer Associated Fibroblasts: Naughty Neighbors That Drive Ovarian Cancer Progression

Ovarian cancer is the most lethal gynecologic malignancy, and patient prognosis has not improved significantly over the last several decades. In order to improve therapeutic approaches and patient outcomes, there is a critical need for focused research towards better understanding of the disease. Recent findings have revealed that the tumor microenvironment plays an essential role in promoting cancer progression and metastasis. The tumor microenvironment consists of cancer cells and several different types of normal cells recruited and reprogrammed by the cancer cells to produce factors beneficial to tumor growth and spread. These normal cells present within the tumor, along with the various extracellular matrix proteins and secreted factors, constitute the tumor stroma and can compose 10–60% of the tumor volume. Cancer associated fibroblasts (CAFs) are a major constituent of the tumor microenvironment, and play a critical role in promoting many aspects of tumor function. This review will describe the various hypotheses about the origin of CAFs, their major functions in the tumor microenvironment in ovarian cancer, and will discuss the potential of targeting CAFs as a possible therapeutic approach.

FAP Delineates Heterogeneous and Functionally Divergent Stromal Cells in Immune-Excluded Breast Tumors

Cancer-associated fibroblasts (CAFs) are generally associated with poor clinical outcome. CAFs support tumor growth in a variety of ways and can suppress antitumor immunity and response to immunotherapy. However, a precise understanding of CAF contributions to tumor growth and therapeutic response is lacking. Discrepancies in this field of study may stem from heterogeneity in the composition and function of fibroblasts in the tumor microenvironment. Furthermore, it remains unclear whether CAFs directly interact with and suppress T cells. Here, mouse and human breast tumors were used to examine stromal cells expressing fibroblast activation protein (FAP), a surface marker for CAFs. Two discrete populations of FAP⁺ mesenchymal cells were identified on the basis of podoplanin (PDPN) expression: a FAP⁺PDPN⁺ population of CAFs and a FAP⁺PDPN^- population of cancer-associated pericytes (CAPs). Although both subsets expressed extracellular matrix molecules, the CAF transcriptome was enriched in genes associated with TGFβ signaling and fibrosis compared with CAPs. In addition, CAFs were enriched at the outer edge of the tumor, in close contact with T cells, whereas CAPs were localized around vessels. Finally, FAP⁺PDPN⁺ CAFs suppressed the proliferation of T cells in a nitric oxide-dependent manner, whereas FAP⁺PDPN^- pericytes were not immunosuppressive. Collectively, these findings demonstrate that breast tumors contain multiple populations of FAP-expressing stromal cells of dichotomous function, phenotype, and location.

Hyaluronan, Cancer-Associated Fibroblasts and the Tumor Microenvironment in Malignant Progression

This review summarizes the roles of CAFs in forming a “cancerized” fibrotic stroma favorable to tumor initiation and dissemination, in particular highlighting the functions of the extracellular matrix component hyaluronan (HA) in these processes. The structural complexity of the tumor and its host microenvironment is now well appreciated to be an important contributing factor to malignant progression and resistance-to-therapy. There are multiple components of this complexity, which include an extensive remodeling of the extracellular matrix (ECM) and associated biomechanical changes in tumor stroma. Tumor stroma is often fibrotic and rich in fibrillar type I collagen and hyaluronan (HA). Cancer-associated fibroblasts (CAFs) are a major source of this fibrotic ECM. CAFs organize collagen fibrils and these biomechanical alterations provide highways for invading carcinoma cells either under the guidance of CAFs or following their epithelial to mesenchymal transition (EMT). The increased HA metabolism of a tumor microenvironment instructs carcinoma initiation and dissemination by performing multiple functions. The key effects of HA reviewed here are its role in activating CAFs in pre-malignant and malignant stroma, and facilitating invasion by promoting motility of both CAFs and tumor cells, thus facilitating their invasion. Circulating CAFs (cCAFs) also form heterotypic clusters with circulating tumor cells (CTC), which are considered to be pre-cursors of metastatic colonies. cCAFs are likely required for extravasation of tumors cells and to form a metastatic niche suitable for new tumor colony growth. Therapeutic interventions designed to target both HA and CAFs in order to limit tumor spread and increase response to current therapies are discussed.

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

Although it is established as a marker of cancer-associated fibroblasts, the expression of fibroblast activation protein (FAP) is not restricted to stromal cells; its expression in multiple types of tumor cell and its pro-tumor functions have been reported. However, the role of FAP in angiogenesis in osteosarcoma remains uncharacterized. In the present study, it was identified that the mRNA and protein expression levels of FAP and vascular endothelial growth factor-A (VEGF-A) corresponded to each other in MG63, U2-OS and HOS osteosarcoma cells. Subsequent to upregulating FAP in MG63 cells, VEGF-A mRNA and protein expression significantly increased; subsequent to downregulating FAP in U2-OS cells, VEGF-A mRNA and protein expression significantly declined. These changes in VEGF-A level were also detected in the cell supernatant with ELISA. Conditioned medium (CM) from MG63 cells overexpressing FAP promoted the phosphorylation of AKT and extracellular signal-regulated kinase (ERK) in human umbilical vein endothelial cells (HUVECs), as well as the proliferation rate. The CM from U2-OS cells with FAP knockdown inhibited the proliferation rate of HUVECs. The phosphorylation of AKT and ERK was increased in MG63 cells overexpressing FAP, but reduced in U2-OS cells with FAP knockdown. Furthermore, treatment with the AKT inhibitor LY294002 or the ERK inhibitor U0126 inhibited the upregulation of VEGF-A induced by FAP expression. Collectively, the results suggest that FAP expression in osteosarcoma cells promotes angiogenesis.

Nectin-1 expression in cancer-associated fibroblasts is a predictor of poor prognosis for pancreatic ductal adenocarcinoma

PURPOSE

Nectin-1 is a cell adhesion molecule that regulates the formation of adherens junctions and tight junctions. We measured the expression of nectin-1 in cancer-associated fibroblasts (CAFs) in patients with pancreatic ductal adenocarcinoma (PDAC).

METHODS

Nectin-1 expression was measured via immunohistochemistry using tissue microarray blocks constructed from resected PDAC tissue from 258 patients. We screened for associations between nectin-1 expression and clinicopathological parameters. According to the percentage of CAFs stained, expression was classified as negative at ≤ 30% and positive at > 30%.

RESULTS

Nectin-1 expression was confirmed in CAFs from 64 patients (24.8%), and was associated with lymph node metastasis (p = 0.016), advanced Union for International Cancer Control stage (p = 0.016), perineural invasion (p = 0.022), pancreatic head tumors (p = 0.023), and shorter overall survival (p = 0.003). Multivariate analysis revealed that nectin-1 expression in CAFs was an independent prognostic factor (p = 0.038).

CONCLUSIONS

Diffuse nectin-1 expression in the CAFs of PDAC patients is associated with invasion, metastasis, and shorter survival.

Fibroblast activation protein-α in tumor cells promotes colorectal cancer angiogenesis via the Akt and ERK signaling pathways

Fibroblast activation protein-α (FAP-α) is a cell surface serine protease of the post-prolyl peptidase family, and stromal FAP-α expression may serve important functions in tumor occurrence and progression. In recent years, FAP-α expression in tumor cells has been detected in a number of types of tumor, and its roles in tumor growth and metastasis have been reported. However, the presence of FAP-α in colorectal cancer (CRC) cells lacks sufficient evidence and its role in angiogenesis remains unknown. The present study confirmed FAP-α expression in CRC cells at the tissue and cellular level, using immunohistochemistry and western blot analysis, respectively; it additionally identified that FAP-α in CRC cells was positively associated with vascular endothelial growth factor (VEGF)-A expression and microvessel density in stained tissue samples for the first time. In addition, western blotting identified that FAP-α overexpression in SW1116 cells significantly upregulated VEGF-A expression, and silencing of FAP-α in HT29 cells markedly inhibited VEGF-A expression. Survival analysis demonstrated that patients with high expression of FAP-α and VEGF-A had the shortest survival time. To detect the effects of FAP-α on human umbilical vein endothelial cells (HUVECs), conditioned medium (CM) from CRC cell lines was used and it was identified that CM from SW1116 cells with overexpressed FAP-α exhibited significantly increased VEGF-R2, phosphorylated extracellular signal-regulated kinase (p-ERK) and p-RAC-α serine/threonine-protein kinase (Akt) in HUVECs, in addition to the proliferation rate. Conversely, CM from HT29 cells with FAP-α silenced exhibited a significantly inhibited proliferation rate. Molecular mechanism analysis demonstrated that p-ERK and p-Akt in SW1116 and HT29 cells were affected by alterations in FAP-α expression, and treatment with a p-ERK inhibitor (U0126) and p-Akt inhibitor (LY294002) ameliorated VEGF-A upregulation induced by FAP-α overexpression. All the results confirmed the presence of FAP-α in CRC cells and suggested that FAP-α may effectively promote angiogenesis in CRC via the Akt and ERK signaling pathways.

Fibroblast activation protein-α promotes the growth and migration of lung cancer cells via the PI3K and sonic hedgehog pathways

A characteristic of the epithelial-to-mesenchymal transition in cancer cells is the upregulation of mesenchymal markers. Fibroblast activation protein α (FAPα) is predominantly expressed by stromal fibroblasts. Previous studies have demonstrated that FAPα is also expressed by certain epithelium-derived cancer cells and is involved in the regulation of certain signaling pathways. One of our previous studies showed that FAPα promoted the proliferation of breast cancer cells via the phosphatidylinositol-3-kinase (PI3K) signaling pathway. In the present study, the A549 adenocarcinoma (AC) and SK-MES-1 squamous cell carcinoma (SCC) lung cancer cell lines were transfected with FAPα. The FAPα-expressing SK-MES-1 cells exhibited an increased growth rate, whereas the FAPα-expressing A549 cells exhibited a similar growth rate, compared with respective empty vector-transfected control cells. Electric cell-substrate impedance sensing (ECIS)-based attachment and wound-healing assays showed that the overexpression of FAPα markedly increased the adhesive and migratory properties of the SK-MES-1 cells but not those of the A549 cells. Additionally, inhibitors of focal adhesion kinase, agonist-induced phospholipase C, neural Wiskott-Aldrich syndrome protein, extracellular signal-regulated kinase, Rho-associated protein kinase, PI3K, and sonic hedgehog (SHH) were used to evaluate the interaction between FAPα and signaling pathways. Only the inhibitors of SHH and PI3K inhibited the increased motility of the FAPα-expressing SK-MES-1 cells. Western blot analysis confirmed the activation of PI3K/AKT and SHH/GLI family zinc finger 1 signaling in the FAPα-expressing SK-MES-1 cells. These results revealed that FAPα promoted the growth, adhesion and migration of lung SCC cells. In addition, FAPα regulated lung cancer cell function, potentially via the PI3K and SHH pathways. Further investigations are required to examine the role of FAPα in lung AC cells.

Palladin mediates stiffness-induced fibroblast activation in the tumor microenvironment

Mechanical properties of the tumor microenvironment have emerged as key factors in tumor progression. It has been proposed that increased tissue stiffness can transform stromal fibroblasts into carcinoma-associated fibroblasts. However, it is unclear whether the three to five times increase in stiffness seen in tumor-adjacent stroma is sufficient for fibroblast activation. In this study we developed a three-dimensional (3D) hydrogel model with precisely tunable stiffness and show that a physiologically relevant increase in stiffness is sufficient to lead to fibroblast activation. We found that soluble factors including CC-motif chemokine ligand (CCL) chemokines and fibronectin are necessary for this activation, and the combination of C-C chemokine receptor type 4 (CCR4) chemokine receptors and β1 and β3 integrins are necessary to transduce these chemomechanical signals. We then show that these chemomechanical signals lead to the gene expression changes associated with fibroblast activation via a network of intracellular signaling pathways that include focal adhesion kinase (FAK) and phosphoinositide 3-kinase (PI3K). Finally, we identify the actin-associated protein palladin as a key node in these signaling pathways that result in fibroblast activation.

Cancer-associated fibroblasts attenuate Cisplatin-induced apoptosis in ovarian cancer cells by promoting STAT3 signaling

One of the main reasons for treatment failure in ovarian cancer is acquired drug resistance. Cancer associated fibroblasts (CAFs) are known to enhance chemoresistance in many human tumors. However, its contributions to chemoresistance acquisition in ovarian cancer are not well understood. Here, we provide the first evidence that the conditioned medium of CAFs (CAFs-CM) could attenuate the sensitivity to Cisplatin in A2780 and ES2 ovarian cancer cells and protect them from Cisplatin-induced apoptosis. We found the expression level of two anti-apoptotic proteins, Bcl-2 and Survivin, as well as their upstream controller p-STAT3 were significantly increased when ovarian cancer cells were exposed to CAFs-CM. Furthermore, inhibition of STAT3 signaling with Cryptotanshinone could down-regulate the expression of Bcl-2 and Survivin, thus weaken the post-target resistance to Cispaltin mediating by CAFs-CM in ovarian cancer cells. In conclusion, our data suggested that CAFs could activate the anti-apoptotic STAT3 signaling, thereby decrease the Cisplatin-induced apoptosis and promote chemoresistance in ovarian cancer.

Bioinformatics-Based Identification of MicroRNA-Regulated and Rheumatoid Arthritis-Associated Genes

MicroRNAs (miRNAs) act as epigenetic markers and regulate the expression of their target genes, including those characterized as regulators in autoimmune diseases. Rheumatoid arthritis (RA) is one of the most common autoimmune diseases. The potential roles of miRNA-regulated genes in RA pathogenesis have greatly aroused the interest of clinicians and researchers in recent years. In the current study, RA-related miRNAs records were obtained from PubMed through conditional literature retrieval. After analyzing the selected records, miRNA targeted genes were predicted. We identified 14 RA-associated miRNAs, and their sub-analysis in 5 microarray or RNA sequencing (RNA-seq) datasets was performed. The microarray and RNA-seq data of RA were also downloaded from NCBI Gene Expression Omnibus (GEO) and Sequence Read Archive (SRA), analyzed, and annotated. Using a bioinformatics approach, we identified a series of differentially expressed genes (DEGs) by comparing studies on RA and the controls. The RA-related gene expression profile was thus obtained and the expression of miRNA-regulated genes was analyzed. After functional annotation analysis, we found GO molecular function (MF) terms significantly enriched in calcium ion binding (GO: 0005509). Moreover, some novel dysregulated target genes were identified in RA through integrated analysis of miRNA/mRNA expression. The result revealed that the expression of a number of genes, including ROR2, ABI3BP, SMOC2, etc., was not only affected by dysregulated miRNAs, but also altered in RA. Our findings indicate that there is a close association between negatively correlated mRNA/miRNA pairs and RA. These findings may be applied to identify genetic markers for RA diagnosis and treatment in the future.

Ovarian cancer microenvironment: implications for cancer dissemination and chemoresistance acquisition

Ovarian adenocarcinoma is characterized by a late detection, dissemination of cancer cells into the whole peritoneum, and the frequent acquisition of chemoresistance. If these particularities can be explained in part by intrinsic properties of ovarian cancer cells, an increased number of studies show the importance of the tumor microenvironment in tumor progression. Ovarian cancer cells can regulate the composition of their stroma in promoting the formation of ascitic fluid, rich in cytokines and bioactive lipids, and in stimulating the differentiation of stromal cells into a pro-tumoral phenotype. In return, cancer-associated fibroblasts, cancer-associated mesenchymal stem cells, tumor-associated macrophages, or other peritoneal cells, such as adipocytes and mesothelial cells can regulate tumor growth, angiogenesis, dissemination, and chemoresistance. This review focuses on the current knowledge about the roles of stromal cells and the associated secreted factors on tumor progression. We also summarize the different studies showing that targeting the microenvironment represents a great potential for improving the prognosis of patients with ovarian adenocarcinoma.

Targeting mitosis-regulating genes in cisplatin-sensitive and -resistant melanoma cells: A live-cell RNAi screen displays differential nucleus-derived phenotypes

Chemoresistance in malignant melanoma remains an unresolved clinical issue. In the search for novel molecular targets, a live-cell high-content RNAi screen based on gene expression data was performed in cisplatin-sensitive and cisplatin-resistant MeWo melanoma cells, Mel-28 cells and a melanocyte cell line. Cells were exposed to 91 siRNAs and distinct nucleus-derived phenotypes such as cell division, cell death and migration phenotypes were detected by time-lapse microscopy over 60 h. Using this approach, cisplatin-sensitive and cisplatin-resistant melanoma cells were compared by automated image analysis and visual inspection. In cisplatin-sensitive MeWo melanoma cells, 14 genes were identified that showed distinct phenotype abnormalities after exposure to gene-specific siRNAs. In cisplatin-resistant MeWo cells, five genes were detected. Nine genes were detected whose knock-down led to differential nuclear phenotypes in cisplatin-sensitive and -resistant cells. In Mel-28 cells, nine genes were identified which induced nuclear phenotypes including all eight genes which were identified in cisplatin-resistant MeWo cells. An analogous RNAi screen on melanocytes revealed no detectable phenotype abnormalities after RNAi. Pathway analysis showed in cisplatin-sensitive MeWo cells and Mel-28 cells an enrichment of at least three genes in major mitotic pathways. We hereby show that siRNA screening may help to identify tumor-specific genes leading to phenotype abnormalities. These genes may serve as potential therapeutic targets in the treatment of melanoma.

Expression levels of seprase/FAPα and DPPIV/CD26 in epithelial ovarian carcinoma

Dipeptidyl peptidase IV (DPPIV; also known as cluster of differentiation 26) and the surface-expressed protease, seprase [also known as fibroblast activation protein alpha (FAPα)], are able to degrade the extracellular matrix; therefore, they are involved in malignant cell invasion and metastasis. However, the prognostic implications of their overexpression in carcinomas remain controversial. The aim of the present study was to investigate the expression and potential prognostic effects of DPPIV and seprase in cases of ovarian carcinoma. Immunohistochemical analysis (IHC) was performed to assess the protein expression of DPPIV and seprase/FAPα in 199 patients (malignant epithelial ovarian cancer, 128; borderline ovarian tumors, 41; and benign ovarian tumors, 30). In addition, in situ hybridization was used to detect the mRNA expression levels of DPPIV and seprase in 86 malignant epithelial ovarian cancer samples. IHC revealed positive staining for seprase and DPPIV proteins in 110/128 (85.94%) and 106/128 (82.81%) patients with ovarian cancer, respectively. Seprase and DPPIV protein expression was associated with lymph node metastasis and the International Federation of Gynecology and Obstetrics stage. By contrast, no significant correlation was detected between the proteins and the patient age or histological grade and type of tumor. Immunostaining was stronger in the cancerous tissues compared with the borderline and benign tissues. Increased levels of seprase, but not DPPIV, were significantly associated with a shorter disease-free survival (P=0.033). Further analysis revealed that 96.5 (83/86) and 97.67% (84/86) of the malignant epithelial ovarian cancer samples stained positively for seprase and DPPIV mRNA, respectively. Therefore, DPPIV and seprase may be involved in the development of ovarian cancer, and that they are potential predictive markers of epithelial ovarian carcinoma.

Characterization of dedifferentiating human mature adipocytes from the visceral and subcutaneous fat compartments: fibroblast-activation protein alpha and dipeptidyl peptidase 4 as major components of matrix remodeling

Mature adipocytes can reverse their phenotype to become fibroblast-like cells. This is achieved by ceiling culture and the resulting cells, called dedifferentiated fat (DFAT) cells, are multipotent. Beyond the potential value of these cells for regenerative medicine, the dedifferentiation process itself raises many questions about cellular plasticity and the pathways implicated in cell behavior. This work has been performed with the objective of obtaining new information on adipocyte dedifferentiation, especially pertaining to new targets that may be involved in cellular fate changes. To do so, omental and subcutaneous mature adipocytes sampled from severely obese subjects have been dedifferentiated by ceiling culture. An experimental design with various time points along the dedifferentiation process has been utilized to better understand this process. Cell size, gene and protein expression as well as cytokine secretion were investigated. Il-6, IL-8, SerpinE1 and VEGF secretion were increased during dedifferentiation, whereas MIF-1 secretion was transiently increased. A marked decrease in expression of mature adipocyte transcripts (PPARγ2, C/EBPα, LPL and Adiponectin) was detected early in the process. In addition, some matrix remodeling transcripts (FAP, DPP4, MMP1 and TGFβ1) were rapidly and strongly up-regulated. FAP and DPP4 proteins were simultaneously induced in dedifferentiating mature adipocytes supporting a potential role for these enzymes in adipose tissue remodeling and cell plasticity.