Novel fusion protein PK5-RL-Gal-3C inhibits hepatocellular carcinoma via anti-angiogenesis and cytotoxicity

Galectin-3 (Gal-3), the only chimeric β-galactosides-binding lectin, consists of Gal-3N (N-terminal regulatory peptide) and Gal-3C (C-terminal carbohydrate-recognition domain). Interestingly, Gal-3C could specifically inhibit endogenous full-length Gal-3 to exhibit anti-tumor activity. Here, we aimed to further improve the anti-tumor activity of Gal-3C via developing novel fusion proteins.PK5 (the fifth kringle domain of plasminogen) was introduced to the N-terminus of Gal-3C via rigid linker (RL) to generate novel fusion protein PK5-RL-Gal-3C. Then, we investigated the anti-tumor activity of PK5-RL-Gal-3C in vivo and in vitro by using several experiments, and figured out their molecular mechanisms in anti-angiogenesis and cytotoxicity to hepatocellular carcinoma (HCC).Our results show that PK5-RL-Gal-3C can inhibit HCC both in vivo and in vitro without obvious toxicity, and also significantly prolong the survival time of tumor-bearing mice. Mechanically, we find that PK5-RL-Gal-3C inhibits angiogenesis and show cytotoxicity to HCC. In detail, HUVEC-related and matrigel plug assays indicate that PK5-RL-Gal-3C plays an important role in inhibiting angiogenesis by regulating HIF1α/VEGF and Ang-2 both in vivo and in vitro. Moreover, PK5-RL-Gal-3C induces cell cycle arrest at G1 phase and apoptosis with inhibition of Cyclin D1, Cyclin D3, CDK4, and Bcl-2, but activation of p27, p21, caspase-3, -8 and -9.Novel fusion protein PK5-RL-Gal-3C is potent therapeutic agent by inhibiting tumor angiogenesis in HCC and potential antagonist of Gal-3, which provides new strategy for exploring novel antagonist of Gal-3 and promotes their application in clinical treatment.