Brain metastases are a very common and serious complication of oncological diseases. Despite the vast progress in multimodality treatment, brain metastases significantly decrease the quality of life and prognosis of patients. Therefore, identifying new targets in the microenvironment of brain metastases is desirable. Fibroblast activation protein (FAP) is a transmembrane serine protease typically expressed in tumour-associated stromal cells. Due to its characteristic presence in the tumour microenvironment, FAP represents an attractive theranostic target in oncology. However, there is little information on FAP expression in brain metastases. In this study, we quantified FAP expression in samples of brain metastases of various primary origin and characterised FAP-expressing cells. We have shown that FAP expression is significantly higher in brain metastases in comparison to non-tumorous brain tissues, both at the protein and enzymatic activity levels. FAP immunopositivity was localised in regions rich in collagen and containing blood vessels. We have further shown that FAP is predominantly confined to stromal cells expressing markers typical of cancer-associated fibroblasts (CAFs). We have also observed FAP immunopositivity on tumour cells in a portion of brain metastases, mainly originating from melanoma, lung, breast, and renal cancer, and sarcoma. There were no significant differences in the quantity of FAP protein, enzymatic activity, and FAP+ stromal cells among brain metastasis samples of various origins, suggesting that there is no association of FAP expression and/or presence of FAP+ stromal cells with the histological type of brain metastases. In summary, we are the first to establish the expression of FAP and characterise FAP-expressing cells in the microenvironment of brain metastases. The frequent upregulation of FAP and its presence on both stromal and tumour cells support the use of FAP as a promising theranostic target in brain metastases.

• Klíčová slova
• Brain metastases, cancer-associated fibroblasts, fibroblast activation protein, theranostics, tumour stroma,
• MeSH
• fibroblasty patologie   MeSH
• individualizovaná medicína MeSH
• karcinom z renálních buněk * patologie   MeSH
• kvalita života MeSH
• lidé MeSH
• membránové proteiny metabolismus   MeSH
• nádorové mikroprostředí MeSH
• nádory ledvin * patologie   MeSH
• nádory mozku * patologie   MeSH
• serinové endopeptidasy metabolismus   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• membránové proteiny MeSH
• serinové endopeptidasy MeSH

Fibroblast activation protein (FAP) is a membrane-bound protease that is upregulated in a wide range of tumours and viewed as a marker of tumour-promoting stroma. Previously, we demonstrated increased FAP expression in glioblastomas and described its localisation in cancer and stromal cells. In this study, we show that FAP+ stromal cells are mostly localised in the vicinity of activated CD105+ endothelial cells and their quantity positively correlates with glioblastoma vascularisation. FAP+ mesenchymal cells derived from human glioblastomas are non-tumorigenic and mostly lack the cytogenetic aberrations characteristic of glioblastomas. Conditioned media from these cells induce angiogenic sprouting and chemotaxis of endothelial cells and promote migration and growth of glioma cells. In a chorioallantoic membrane assay, co-application of FAP+ mesenchymal cells with glioma cells was associated with enhanced abnormal angiogenesis, as evidenced by an increased number of erythrocytes in vessel-like structures and higher occurrence of haemorrhages. FAP+ mesenchymal cells express proangiogenic factors, but in comparison to normal pericytes exhibit decreased levels of antiangiogenic molecules and an increased Angiopoietin 2/1 ratio. Our results show that FAP+ mesenchymal cells promote angiogenesis and glioma cell migration and growth by paracrine communication and in this manner, they may thus contribute to glioblastoma progression.

• Klíčová slova
• angiogenesis, angiopoietin, fibroblast activation protein, glioblastoma, microenvironment, seprase, vessel destabilisation,
• Publikační typ
• časopisecké články MeSH

The proline-specific serine protease fibroblast activation protein (FAP) can participate in the progression of malignant tumors and represents a potential diagnostic and therapeutic target. Recently, we demonstrated an increased expression of FAP in glioblastomas, particularly those of the mesenchymal subtype. Factors controlling FAP expression in glioblastomas are unknown, but evidence suggests that transforming growth factor beta (TGFbeta) can trigger mesenchymal changes in these tumors. Here, we investigated whether TGFbeta promotes FAP expression in transformed and stromal cells constituting the glioblastoma microenvironment. We found that both FAP and TGFbeta-1 are upregulated in glioblastomas and display a significant positive correlation. We detected TGFbeta-1 immunopositivity broadly in glioblastoma tissues, including tumor parenchyma regions in the immediate vicinity of FAP-immunopositive perivascular stromal cells. Wedemonstrate for the first time that TGFbeta-1 induces expression of FAP in non-stem glioma cells, pericytes, and glioblastoma-derived endothelial and FAP+ mesenchymal cells, but not in glioma stem-like cells. In glioma cells, this effect is mediated by the TGFbeta type I receptor and canonical Smad signaling and involves activation of FAP gene transcription. We further present evidence of FAP regulation by TGFbeta-1 secreted by glioma cells. Our results provide insight into the previously unrecognized regulation of FAP expression by autocrine and paracrine TGFbeta-1 signaling in a broad spectrum of cell types present in the glioblastoma microenvironment.

• Klíčová slova
• Smad2, fibroblast activation protein, glioblastoma, regulation of expression, seprase, signaling, transforming growth factor beta, tumor microenvironment,
• MeSH
• endopeptidasy genetika   metabolismus   MeSH
• fluorescenční protilátková technika MeSH
• fosforylace MeSH
• glioblastom etiologie   metabolismus   patologie   MeSH
• imunohistochemie MeSH
• kultivované buňky MeSH
• lidé MeSH
• membránové proteiny genetika   metabolismus   MeSH
• nádorové buněčné linie MeSH
• nádorové mikroprostředí účinky léků   genetika   MeSH
• regulace genové exprese u nádorů * účinky léků   MeSH
• transformující růstový faktor beta1 metabolismus   farmakologie   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• endopeptidasy MeSH
• fibroblast activation protein alpha MeSH Prohlížeč
• membránové proteiny MeSH
• TGFB1 protein, human MeSH Prohlížeč
• transformující růstový faktor beta1 MeSH

Fibroblast activation protein (FAP, seprase) is a serine protease with post-proline dipeptidyl peptidase and endopeptidase enzymatic activity. FAP is upregulated in several tumor types, while its expression in healthy adult tissues is scarce. FAP molecule itself and FAP+ stromal cells play an important although probably context-dependent and tumor type-specific pathogenetic role in tumor progression. We provide an overview of FAP expression under both physiological and pathological conditions with focus on human malignancies. We also review and critically analyze the results of studies which used various strategies for the therapeutic targeting of FAP including the use of low molecular weight inhibitors, FAP activated prodrugs, anti-FAP antibodies and their conjugates, FAP-CAR T cells, and FAP vaccines. A unique enzymatic activity and selective expression in tumor microenvironment make FAP a promising therapeutic target. A better understanding of its role in individual tumor types, careful selection of patients, and identification of suitable combinations with currently available anticancer treatments will be critical for a successful translation of preclinically tested approaches of FAP targeting into clinical setting.

• MeSH
• cílená molekulární terapie metody   MeSH
• endopeptidasy MeSH
• inhibitory enzymů terapeutické užití   MeSH
• lidé MeSH
• membránové proteiny antagonisté a inhibitory   genetika   metabolismus   MeSH
• nádorové mikroprostředí účinky léků   genetika   MeSH
• nádory farmakoterapie   genetika   metabolismus   MeSH
• regulace genové exprese enzymů účinky léků   MeSH
• regulace genové exprese u nádorů účinky léků   MeSH
• serinové endopeptidasy genetika   metabolismus   MeSH
• želatinasy antagonisté a inhibitory   genetika   metabolismus   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• přehledy MeSH
• Názvy látek
• endopeptidasy MeSH
• fibroblast activation protein alpha MeSH Prohlížeč
• inhibitory enzymů MeSH
• membránové proteiny MeSH
• serinové endopeptidasy MeSH
• želatinasy MeSH