Metastasis remains the leading cause of cancer-related death, and certain so-called aggressive tumors, such as triple-negative breast cancers or pancreatic cancers, are characterized by a strong propensity to form secondary foci. In the absence of fully effective treatments against this dissemination, innovative therapeutic approaches are being sought. Among these, extracellular vesicles (EVs) are attracting growing interest: these natural mediators of cell-to-cell communication can transfer genetic and trophic material to recipient cells, without the risks associated with the injection of whole living cells. They have already been tested in humans in phase I and II clinical trials, which demonstrated their safety across various indications.
This work builds on previous findings that established the opposing roles of two transcription factors of the NFAT family in breast cancer: NFAT1 (NFATc2) exerts a pro-invasive function, whereas NFAT3 (NFATc4) possesses anti-invasive properties that limit the aggressiveness of luminal tumor cells. The aim was to determine whether this inhibitory function could be conveyed by EVs. To this end, vesicles were produced by poorly invasive mammary cell lines expressing NFAT3, then isolated by differential centrifugation and ultracentrifugation at 120,000 g, before being characterized by nanoparticle tracking analysis (NTA) and by detection of the CD63 and CD81 markers. Their effect was assessed in vitro in Matrigel chamber invasion assays, on proliferation and apoptosis in 2D cultures and spheroids, and then in vivo in a mouse model.
The EVs produced by these cells proved capable of blocking the in vitro invasion of aggressive cancer cells of various origins. In cooperation with macrophages, they inhibited proliferation and induced apoptosis of tumor cells, an effect enhanced by overexpression of NFAT3 in the producing cells. These observations were extended to a mouse model of breast cancer, in which luciferase-expressing MDA-MB-231 cells were implanted into the mammary fat pad. Weekly injection of inhibitory EVs into the tumor, followed by measurement of tumor volume and bioluminescence imaging of axillary metastases, revealed a clear impact on tumor growth and metastatic dissemination.
This work thus identifies extracellular vesicles derived from NFAT3-expressing cells as an antitumor tool capable of curbing cancer development and metastasis formation. The approach has the advantage of harnessing an endogenous inhibitory function and transferring it via natural vectors whose safety has already been documented in humans.