[Regulatory effect of Epimedium flavonoid microparticles on pulmonary pre-metastatic microenvironment]

Tumor metastasis is the main cause of death in clinical patients. The proposal of the pre-metastatic microenvironment hypothesis offers a new research direction for tumor metastasis. Targeting and inhibiting the activation of the stimulator of interferon genes(STING) signals by tumor cell-derived microparticles may help reduce tumor metastasis. This study constructed a pre-metastatic microenvironment and pulmonary metastasis model using recombinant adeno-associated virus vector-mediated short hairpin RNA interference of STING(rAAV STING shRNA) to investigate the effects of STING interference on the pre-metastatic microenvironment and the impact of total Epimedium flavonoids(EFs) as an intervention. Drug-containing microparticles were prepared by incubating mouse Lewis lung cancer(LLC) cells with the total EFs(EFs-LLC-MPs), and EFs-LLC-MPs were characterized by measuring the average particle size, polydispersity index, zeta potential, and release profile. Western blot was used to examine changes in pre-metastatic microenvironment markers in mouse alveolar epithelial cells(MLE-12) after treatment with microparticles or total EFs. Drug loading capacity and the uptake of microparticles by MLE-12 and mouse alveolar macrophages(MH-S) cells were determined using HPLC and flow cytometry. The uptake experiments showed that after nasal administration of rAAV STING shRNA, STING expression was significantly inhibited, and the markers of the pre-metastatic microenvironment were markedly reduced. Micro-CT results indicated a reduction in lung metastases and nodules, and the anti-metastatic effect of total EFs was affected. The results showed that the microparticles were membrane vesicles with a particle size of(373.17±3.18)nm, a Zeta potential of(-35.40±1.08)mV, a protein concentration of 562.62 μg·mL~(-1), and a drug loading of 0.060 9 μg per microgram of protein. These microparticles were effectively taken up by MLE-12 and MH-S cells. Treatment of MLE-12 and MH-S cells with EFs-LLC-MPs reduced the expression of pre-metastatic microenvironment markers such as fibronectin and lysyl oxidase(LOX). Based on these findings, it was confirmed that STING was involved in the regulation of the formation of the pre-metastatic microenvironment in the lungs. Furthermore, total EFs microparticles were successfully prepared, showing potential to intervene in the inflammatory pre-metastatic microenvironment, which could be promising for controlling tumor metastasis.