A combined treatment with Ursolic acid and Solasodine inhibits colorectal cancer progression through the AKT1/ERK1/2-GSK-3β-β-catenin axis.

Background: Conventional chemotherapy medications are inadequate for managing the primary or acquired drug resistance, high toxicity, and adverse effects of colorectal cancer (CRC) treatment. Ursolic acid (UA) and Solasodine (Sol) are natural compounds found in a wide variety of traditional medicinal plants, as well as in many fruits and vegetables, such as Actinidia arguta (Sieb. & Zucc) Planch and Solanum nigrum L.. These compounds exhibit significant anti-tumor activity. Recent investigations have demonstrated that a combination strategy using natural products exhibits greater potential in CRC treatment compared to a single-drug strategy.

Purpose: This study aimed to elucidate the potential of UA-Sol synergy against CRC and to investigate the mechanism of action involved in inducing apoptosis and inhibiting metastasis through the AKT1/ERK1/2-GSK-3β-β-catenin axis.

Methods: The optimal ratio of UA-Sol and its synergistic effects were explored using an MTT assay combined with the technique of Chou Talalay. The effects of UA-Sol on the apoptosis, autophagy, and metastasis of CRC cells were assessed using Annexin V-FITC/PI, TUNEL, Immunofluorescence, Wound healing, Transwell migration, and western blotting. The core mechanism of action of UA-Sol against CRC was investigated employing network pharmacology prediction combined with CETSA and plasmid transfection. Finally, in vivo validation was conducted using mouse xenograft tumor and lung metastasis models.

Results: The combination of UA and Sol synergistically inhibited CRC cell viability at a molar ratio of 6:24. UA-Sol induced the expression of pro-apoptotic and autophagy genes such as Bax/Bcl-2 and LC3, ultimately leading to apoptosis and autophagy in CRC cells in vitro. In addition, this combination inhibited MMP-9 and promoted the expression of the adhesion protein E-cadherin, thereby inhibiting CRC cell metastasis. Mechanistically, UA-Sol regulated the expression of a downstream protein GSK-3β by targeting AKT1 and ERK1/2 inhibition. This induced a cross-talk between the MAPK cascade pathway and the PI3K/AKT pathway, thereby inhibiting the nuclear translocation of β-catenin and participating in the regulation of CRC cell processes.

Conclusion: UA-Sol inhibited the AKT1/ERK1/2-GSK-3β-β-catenin axis to induce apoptosis, autophagy and anti-metastasis by targeting AKT1 and ERK1/2 inhibition. This dual-target drug combination strategy provides promising insights into the development of novel, safe, and efficient drugs for the treatment of CRC.