Ultrasound-mediated nanobubbles loaded with STAT6 siRNA inhibit TGF-β1-EMT axis in LUSC cells via overcoming the polarization of M2-TAMs

M2-like tumor-associated macrophages (M2-TAMs) are closely correlated with metastasis and poor clinical outcomes in lung squamous cell carcinoma (LUSC). Previous studies have demonstrated that STAT6 is an important signaling molecule involved in the polarization of M2-TAMs, EMT is the main way for TAMs to promote tumor progression. However, little attention has been paid to the effect of STAT6 inhibition on LUSC, and it is difficult to achieve an ideal gene silencing effect in immune cells using traditional gene transfection methods. Here, we investigated the optimal concentration of 12-myristic 13-acetate (PMA), lipopolysaccharide (LPS) for the induction of THP-1 into M1-TAMs and M2-TAMs. The expression of pSTAT6 and STAT6 was confirmed in three types of macrophages, and it was demonstrated that pSTAT6 can be used as a specific target of M2-TAMs derived from THP-1. Ultrasound-mediated nanobubble destruction (UMND) is a non-invasive and safe gene delivery technology. We also synthesized PLGA-PEI nanobubbles (NBs) to load and deliver STAT6 small interfering RNA (siRNA) into M2-TAMs via UMND. The results show that the NBs could effectively load with siRNA and had good biocompatibility. We found that UMND enhanced the transfection efficiency of siRNA, as well as the silencing effect of pSTAT6 and the inhibition of M2-TAMs. Simultaneously, when STAT6 siRNA entered M2-TAMs by UMND, proliferation, migration, invasion and EMT in LUSC cells could be inhibited via the transforming growth factor-β1 (TGF-β1) pathway. Therefore, our results confirm that UMND is an ideal siRNA delivery strategy, revealing its potential to inhibit M2-TAMs polarization and ultimately treat LUSC.