Berberine, also known as a P-glycoprotein inhibitor, is an isoquinoline alkaloid that shows low toxicity and anticancer activities. P-glycoprotein is an energy dependent drug efflux transporter that can reduce drug accumulation within cells by pumping out therapeutic agents. Berberine shows antiproliferative effect in colorectal carcinoma and induced apoptosis. The phosphatidylinositol 3-kinase (PI3K)/AKT/mTOR pathway, is critical in tumor growth and metastasis. The therapeutic potential of PI3K/AKT/mTOR inhibitors and their combinations have led to their active investigation in preclinical and clinical studies for colorectal carcinoma treatment. Dactolisib, also known as NVP-BEZ235, is a dual PI3K and mTOR kinase inhibitor. The current study investigates the synergistic anti-cancer effect of Berberine and Dactolisib on colorectal carcinoma HCT-116 cell line.

Cell viability assay was conducted by resazurine dye and colony forming assay was conducted to determine the cell growth inhibition in HCT-116 cell line when treated with Berberine and Dactolisib. Migration ability of combination treatment of Berberine and Dactolisib was determine by in vitro scratch assay. Cell cycle assay was conducted by staining with propidium iodide to detect the cell distribition of HCT-116 cells. Inracellular uptake of Berberine was detected by fluorescence microscopy. Kinetic analysis and competition assay of both druges were monitored by Ligand tracer to detect the real-time interaction measurements on live cells.

Cytotoxicity of Berberine and Dactolisib was observed in a dose and time dependent manner in colorectal carcinoma HCT-116 cell line. Low doses of Dactolisib (0.25µM and 0.5 µM) showed nearly 50% cell viability when combined with 10 µM Berberine at 48 hours. Co-treatment of Berberine and Dactolisib showed a significant reduction in colony formation and migration ability in HCT-116 cell line. Treatment with Berberine and Dactolisib led to an increase in SubG0 phase of HCT-116 cells, suggesting possible induction in apoptosis. Intracellular uptake of Berberine was higher in combination groups compared to Berberine alone group. Co-treatment of Berberine and Dactolisib reflects the stabilizing effect of Dactolisib on Berberine binding kinetics in HCT-116 cells and ensure prolonged intracellular retention and activity of Berberine. As Berberine a P-glycoprotein inhibitor, this synergistic approach could be a potential combination to overcome drug resistance. Resistant HCT-116 cell line will be used to futher analyze this combination therapy.

These findings suggest a synergistic anti-cancer effect of Berberine and Dactolisib combination on HCT-116 cell line, demonstrating a potential therapy for colorectal carcinoma to overcome drug resistance.