Verbascoside: Identification, Quantification, and Potential Sensitization of Colorectal Cancer Cells to 5-FU by Targeting PI3K/AKT Pathway

Colorectal cancer (CRC) is the third most common cancer mortality worldwide. Although, 5-Fluorouracil (5-FU)-based chemotherapeutic regimens remain the mainstay for treatment of CRC, intrinsic and acquired resistance to 5-FU is the main reason for treatment failure and relapse. Adjunct or add-on therapy, therefore, should be thought of to enhance responsiveness to 5-FU. Verbascoside (VER) is a phenylethanoid glycoside ingredient present in many Plantago species and was widely used in traditional medicine. VER showed antiproliferative effects in many cancer types including CRC. In the present study, VER in Plantago seeds was identified using UPLC-MS/MS and quantified using newly developed and validated UPLC-DAD followed by investigating its potential sensitization of CRC cells to 5-FU in vitro. The potential impact on PI3K/AKT pathway was also investigated. A synergistic cytotoxic interaction between 5-FU and VER besides G1 cell cycle arrest were detected. Enhanced apoptosis mainly by affecting Bax and Bcl-2 and to a lesser extent Bcl-xL and p53 was also observed. Additionally, 5-FU combined to VER was capable of significantly reducing PI3K and p-AKT/total AKT ratio. Overall, these results suggest a potential role of VER as an adjuvant treatment to decrease the resistance of CRC cells to 5-FU possibly by targeting the PI3K/AKT pathway.