Abstract
BACKGROUND/AIM: Oxaliplatin (L-OHP) is absorbed by cancer cells via organic cation transporter1-3 (OCT1-3). However, proton pump inhibitors (PPIs) suppress the function of OCT1-3. This study investigated whether PPIs attenuate the antitumor effect of L-OHP. PATIENTS AND METHODS: Colorectal cancer patients who received FOLFOX (L-OHP + 5-fluorouracil: 5-FU) + bevacizumab therapy at Nagasaki University Hospital from October 1, 2010 to September 30, 2019 were retrospectively investigated. Patients were categorized into two groups with or without PPIs use. Progression-free survival (PFS) between the two groups was compared using the log-rank test. L-OHP was added to the intestinal epithelial Caco-2 cell line with or without the PPI rabeprazole, and then cell viability was analyzed using the WST-8 cell proliferation assay. RESULTS: The median PFS was 11.4 months in the group with PPIs and 9.7 months in the group without PPIs (p=0.736). No significant effect of 1-10 μM rabeprazole was observed on the antitumor effect of L-OHP. Plasma concentrations of rabeprazole at clinical doses are 1.0-1.3 μM. CONCLUSION: Even if L-OHP interacts with PPIs, clinical doses of PPIs were considered to have minimal effect on the antitumor effect of L-OHP.