Inhibition of growth of 5-fluorouracil-resistant gastric cancer cells by sorafenib and synergistic effect of 5-fluorouracil and sorafenib in xenograft models

Abstract

Sorafenib is a multi-kinase inhibitor used for the targeted therapy against cancer. This study investigated the anti-tumor effect of sorafenib in combination with 5-fluorouracil (5-FU) in xenograft models produced using NCI-N87 cells, and tested the potential inhibitory effect of sorafenib on 5-FU-resistant NCI-N87 cells and sphere formation of NCI-N87 cells and 5-FU-resistant NCI-N87 cells. Sorafenib inhibited the growth of NCI-N87 cells in a dose-dependent manner; the mean IC50 of sorafenib was 16.345 ± 5.391 μM. After a 2-hour exposure to sorefenib, phosphorylation levels of MEK and ERK in NCI-N87 cells were reduced dose-dependently. Sorafenib induced the activation of caspase-3 in vitro and apoptosis in vivo. Xenograft mice were established by the subcutaneous implantation of NCI-N87 cells into BALB/c nude mice. To investigate the effect of a combination of sorafenib and 5-FU, four groups of xenograft mice were prepared: vehicle, sorafenib (20 mg/kg/day), 5-FU (50 mg/kg/week), and sorafenib (20 mg/kg/day) + 5-FU (50 mg/kg/week) were prepared. Sorafenib was administered orally once a day and 5-FU was injected intraperitoneally every week for 3 weeks. Sorafenib in combination with 5-FU significantly inhibited the growth of xenograft tumors compared to sorafenib alone or 5-FU alone (P<0.05). 5-FU-resistant NCI-N87 cells were established by the repeated exposure to 5-FU. Sorafenib effectively inhibited the growth of 5-FU-resistant NCI-N87 cells as well as NCI-N87 cells. NCI-N87 cells and 5-FU-resistant NCI-N87 cells were cultured to encourage in sphere cells formation. Sorafenib exposure caused inhibition of sphere formation of both NCI-N87 cells and 5-FU-resistant NCI-N87 cells. Sorafenib in combination with 5-FU has the anti-tumor effect on gastric cancer xenograft models, and sorafenib has the potential inhibitory effect on 5-FU-resistant gastric cancer cells and on sphere formation in gastric cancer cells. These findings suggest that sorafenib may have an important role to overcome resistance to conventional chemotherapy in advanced gastric cancer, and become a clue to target cancer stem cells.