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.

Analysis of the expression of FAP-α protein in 2D-keloid fibroblast cultures and in 3D models of keloid

OBJECTIVE

Keloids arise most often as a result of abnormal wound healing. The lesion characterizes inflammation and fibroproliferation. Fibroblast activation protein alpha (FAP-α) is one of enzymes engaged in keloid formation. It is serine protease that facilitates cells invasion and growth. FAP-α possess also non-enzymatic activity and plays role in activation of cell signaling. The aim of the study was to assess the impact of culture conditions on the proliferation of keloid fibroblasts and the expression of FAP-α. Analysis of utility of 3D models of keloid in in vitro study of pathogenesis of keloids was also made.

METHODS

NHDF and KEL FIB cells were cultured in vitro in 2D cultures and 3D Matrigel models. The viability of cells was assayed spectrophotometrically with WST-1 test. FAP-α protein amount in cell cultures and 3D models was evaluated with the use of ELISA test.

RESULTS

KEL FIB fibroblasts exhibited higher viability than NHDF fibroblasts in all three models of keloid. The expression of FAP-α is different in normal and keloid fibroblasts. In vitro conditions influence the expression of FAP-α in NHDF cells but not in KEL FIB cells.

CONCLUSIONS

This preliminary study has shown that the expression of FAP-α, similarly to other enzymes engaged in keloid formation, is different in keloids in vivo and in in vitro models. FAP-α expression is modulated by in vitro conditions in normal fibroblasts but not in keloid fibroblasts.

TGF-β1-activated cancer-associated fibroblasts promote breast cancer invasion, metastasis and epithelial-mesenchymal transition by autophagy or overexpression of FAP-α

Cancer-associated fibroblasts (CAFs) play an important role in the initiation, metastasis, and invasion of breast cancer. However, whether autophagy acts as a tumor promotion mechanism by inducing epithelial-mesenchymal transition (EMT) is still controversial and remains undefined at the mechanistic levels. In this study, we investigated whether autophagy or FAP-α is required for the invasion, pulmonary metastasis and EMT of breast cancer cells and underlying mechanism. We employed an in vitro model of NIH3T3 fibroblasts treated with H₂O₂ and confirmed that TGF-β1 could convert fibroblasts into CAFs through autophagy under oxidative stress in the tumor microenvironment. Modulation of autophagy by rapamycin, 3-methyladenine or ATG-5 knockdown regulated the expression of CAFs markers, suggesting a role of autophagy in the tumor promotion mechanism of TGF-β1-induced CAFs activation. Furthermore, we established an indirect co-culture model and a mixed xenograft as a corresponding in vivo model. We demonstrated that TGF-β1-activated CAFs promote tumor invasion, pulmonary metastasis and EMT, which act through autophagy and overexpression of FAP-α in both models, while autophagy inhibitor 3-methyladenine blocked these effects induced by TGF-β1-activated CAFs. Moreover, the co-localization of LC3β and EMT marker vimentin in mixed xenograft also revealed that TGF-β1-activated CAFs promote tumor growth, pulmonary metastasis, and EMT program partly through autophagy. In addition, knockdown of FAP-α resulted in reversed EMT and abolished tumor invasion and pulmonary metastasis induced by TGF-β1-activated CAFs. Taken together, we conclude that both autophagy and FAP-α are required for breast cancer cell invasion and metastasis. Targeting autophagy or FAP-α rather than both can serve as a potential approach to improve the prognosis for human breast cancer.

microRNA-30a attenuates TGF-β1-induced activation of pulmonary fibroblast cell by targeting FAP-α

Idiopathic interstitial pulmonary fibrosis is a common diffuse interstitial lung disease and has poor prognosis. And one of the pathological features of it is persistent fibroblast activation. It was reported that microRNA‐30a was down‐regulated in bronchoalveolar lavage fluid from idiopathic pulmonary fibrosis patients. But whether miR‐30a is involved in fibroblast activation and its specific mechanism is unclear. In this study, we aimed to investigate the role of miR‐30a in fibroblast activation induced by TGF‐β1. We found miR‐30a could targetedly suppress FAP‐α expression. In MRC5 cells, miR‐30a was not only involved in regulating the expression of FAP‐α, col1a and α‐SMA induced by TGF‐β1 but also had a role in cell proliferation with or without TGF‐β1 treatment via regulating FAP‐α expression. Thus, the results indicated that miR‐30a alleviated fibroblast activation by regulating the expression of FAP‐α.

The stromal compartments in pancreatic cancer: are there any therapeutic targets?

Pancreatic ductal adenocarcinoma (PDAC) is characterised by an abundant stromal response also known as a desmoplastic reaction. Pancreatic Stellate Cells have been identified as playing a key role in pancreatic cancer desmoplasia. There is accumulating evidence that the stroma contributes to tumour progression and to the low therapeutic response of PDAC patients. In this review we described the main actors of the desmoplastic reaction within PDAC and novel therapeutic approaches that are being tested to block the detrimental function of the stroma.