e12562 Background: Breast cancer has overtaken lung cancer as the most common cancer worldwide. Breast cancer bone metastases can lead to death. How to inhibit the progression of bone metastasis of breast cancer is the key to improve the quality of life of breast cancer patients. In recent years, there have been increasing studies on the therapeutic significance of plant-derived extracellular vesicles (PDEVs), which play an important role in anti-tumor and anti-inflammatory. It is a new potential anti-tumor therapy. According to the Chinese medicine classics, figs have anti-cancer effect, but the main active ingredients are not clear yet. Methods: The exosomes were extracted by differential ultracentrifugation. The breast cancer cells (MDA-MB-231, MCF-7, 4T1, E0771) were treated with 0.1 ug/ml and 0.5 ug/ml fig exosome-like nanoparticles (FELNs) for 48 hours. The proliferation rate was measured by BrdU kit and verified by RT-qPCR. The total RNA from MDA-MB-231 cells treated by FELNs was sequenced to screen the differential genes. Key genes were differentially expressed in MDA-MB-231 and MCF-7 cells and further verified. Animal models of breast cancer in situ and bone metastasis were constructed in mice. FELNs were injected intraperitoneally twice a week, live imaging of small animals was performed on the 14th and 21st day to observe the tumor size and progression of breast cancer, and tibia samples were collected for Trap staining. The bone marrow macrophages of mice were extracted and treated by FELNs. The polarization was detected by RT-qPCR. After the removal of the proteins and nucleic acids in FELNs by protease, DNase and RNase, FELNs intervened in breast cancer cells and macrophages to determine the effective components of the FELNs. Results: After breast cancer cells were treated with FELNs, the proliferation rate was significantly decreased, especially MDA-MB-231 (from 70.3% to 17.7%) and MCF-7 (from 7.32% to 1.63%), and the RNA level of proliferation-related gene were significantly down-regulated. The key gene RN7SL1 was screened by sequencing. Overexpression of RN7SL1 significantly promoted the proliferation of MDA-MB-231 and MCF-7 cells, while the level of proliferation-related gene RNA was significantly up-regulated. FELNs significantly inhibited the tumor size and bone metastasis of breast cancer, and the tibial osteolysis was significantly abated by the treatment of FELNs in tibial Trap staining. After the intervention of FELNs in mouse macrophages, the polarization of M1 macrophages was significantly promoted. The proliferation rate of breast cancer cells increased and the polarization of M1 macrophages disappeared by treatment with protein-free FELNs. Conclusions: The protein components in FELNs inhibit the proliferation of breast cancer cells through RN7SL1, thereby inhibiting the progression of breast cancer bone metastasis.

Mechanism study on fig exosome-like nanoparticles inhibiting the progression of bone metastasis in breast cancer.