A Novel Strategy Conjugating PD-L1 Polypeptide With Doxorubicin Alleviates Chemotherapeutic Resistance and Enhances Immune Response in Colon Cancer

Bruceine a exerts antitumor effect against colon cancer by accumulating ROS and suppressing PI3K/Akt pathway

Bruceine A (BA), a quassic ester from bruceine javanica, regulates diverse intracellular signal transduction pathways and manifests a variety of biological activities, however, its pharmacological mechanism in treating colon cancer (CC) is unclear. In this study, we investigated the anticancer effects of BA on CC cells and the underlying mechanisms. The network pharmacology research indicated that Akt1 and Jun and PI3K/Akt pathways are the predominant targets and critical signaling pathways, respectively, for BA treatment of CC. Meanwhile, molecular docking results implied that BA could conjugate to pivotal proteins in the PI3K/Akt pathway. BA remarkably suppressed the proliferation of CC cells HCT116 and CT26 with 48-h IC50 of 26.12 and 229.26 nM, respectively, and the expression of p-PI3K/p-Akt was restrained by BA at the molecular level as verified by Western blot assay. Further mechanistic studies revealed BA impacted cell cycle-related proteins by regulating the expression of P27 (a protein bridging the PI3K/Akt signaling pathway with cycle-related proteins), arresting the cell cycle in the G2 phase, inhibiting the proliferation of HCT116 and CT26, and facilitated the apoptosis in CC cells by activating the mitochondria-associated apoptosis protein Bax and accumulating reactive oxygen species, in addition to BA apparently inhibited the migration of CC cells. Taken together, our results demonstrated that BA might be a promising chemotherapy drug in the treatment of CC.

Targeted Nanobubbles of PD-L1 mAb Combined with Doxorubicin as a Synergistic Tumor Repressor in Hepatocarcinoma

Purpose

Ultrasound nanobubbles (NBs) can kill tumor cells, mediated by their effects of cavitation and acoustic perforation through ultrasound, while as novel drug carriers, biomaterial-modified NBs release drugs at a target region. In this work, the ultrasound NBs bridged by biotin-streptavidin were prepared simultaneously to be loaded with both programmed death ligand 1 monoclonal antibody (PD-L1 mAb) and doxorubicin (DOX), which are immune checkpoint inhibitors (ICIs) and chemotherapeutic agents, to synergize immunotherapy and chemotherapy combined with sonodynamic therapy (SDT).

Methods

The PD-L1 mAb/DOX NBs, using bridging affinity biotin (BRAB) technology as a bridge, were prepared by thin-film hydration and mechanical oscillation for the targeted delivery of biotinylated PD-L1 mAb and DOX. Characterization and pharmacokinetic studies of PD-L1 mAb/DOX NBs were performed in vitro and in vivo. The antitumor effect of ultrasound-mediated PD-L1 mAb/DOX-NBs was studied in the subcutaneously transplanted tumor of the H22 hepatoma model, and the mechanism of synergistic tumor repression was investigated.

Results

The data of in vitro targeting experiments, contrast-enhanced ultrasound imaging (CEUS), in vivo imaging of the small animals imaging system (IVIS), and frozen sections showed that PD-L1 mAb/DOX-NBs have well-targeted aggregation in the tumor. By observing tumor inhibition rate, tissue cell apoptosis, and apoptosis-related gene and protein expression, the PD-L1 mAb/DOX-NBs group showed the best immunotherapy effects, and its tumor volume and mass inhibition rates were about 69.64% and 75.97%, respectively (P < 0.01). Therefore, blocking the PD-1/PD-L1 pathway could improve immune cells’ tumor-killing ability. Antitumor immune cytokines were further enhanced when combined with DOX-induced tumor cell apoptosis and immunogenic cell death (ICD).

Conclusion

In summary, ultrasound-mediated PD-L1 mAb/DOX-NBs showed significant synergistic antitumor effects, providing a potential combined immunotherapy strategy for HCC.