Ultrasound nanobubble-based combinational strategies of loaded miR-107-3p and CD133 Ab for anti-PD-L1 and anti-hepatocellular cancer stem cells

Background: CD133 is regarded as a marker and target for cancer stem cells (CSCs) in various types of tumors, including hepatocellular carcinoma (HCC). The expressions of CD133 and programmed cell death ligand 1 (PD-L1) in CSCs exhibit a positive feedback regulatory effect. This effect promotes CSC proliferation and immune escape, ultimately leading to tumor progression and poor prognosis.

Methods: CD133-specific antibodies and miR-107-3p loaded nanobubbles (miR-107-3p/CD133 Ab-NBs) were assembled using various techniques, such as the biotin-avidin system and cationic lipid nanobubbles. The relationship between miR-107-3p and PD-L1 was established via a miR-107-3p mimic/inhibitor using RT-qPCR and Western blot methods. The miR-107-3p/CD133 Ab-NBs were characterized, and their pharmacokinetic attributes were studied in combination with ultrasound-targeted microbubble destruction (UTMD). Subsequently, the anti-tumor efficacy and mechanism were scrutinized both in vitro and in vivo.

Results: miR-107-3p/CD133Ab NBs were successfully prepared through CD133Ab conjugation and miR-107-3p loading, yielding an average particle size of 342.0 ± 26.3 nm, and presenting as spherical particles with uniform size and distribution. By using a mouse subcutaneous transplanted tumor model, paired with UTMD, we found that miR-107-3p/CD133Ab-NBs could significantly accumulate at the tumor site, as observed through the IVIS Spectrum system. These nanoparticles showed considerable anti-tumor activity against HCC, both in vitro and in the xenograft mouse model. Further findings indicated that miR-107-3p/CD133Ab-NBs promoted lymphocyte proliferation enhanced the cytotoxic T lymphocyte (CTL) killing activity, and increased cytokine gene expression. This suggests that the combination of miR-107-3p/CD133Ab-NBs with UTMD could enhance anti-cancer immune responses by inhibiting PD-L1 with miR-107-3p and targeting CD133 on the CSCs of HCC.

Conclusions: Our study introduces a novel strategy for ultrasound-targeted microbubbles containing miR-107-3p and CD133Ab. This strategy demonstrated substantial anti-tumor activity against HCC by blocking the positive feedback of CD133 and PD-L1 expression in CSCs. Thus, it reveals a potential advantage of combined miR-107-3p/CD133 Ab-NBs therapy for HCC.