Figure 3. Ubenimex reverses CDDP resistance in vitro by suppressing CD13 expression. (A, B) CDDP-resistant GC cells were pre-treated with Ubenimex (0.2 mg/mL) and pEGFP-N1-CD13 or the combination of both for 24 h, followed by incubation with CDDP at increasing concentrations (0, 2, 4, 8, 16, 32, 64, 100, and 120 μmol/L) for another 48 h. CDDP cytotoxicity towards the indicated cells was manifested as the inhibition rate which was determined by CCK-8 method. The results are expressed as the means±SD of three replicates.*P <0.05, **P<0.01 and #P>0.05 versus CDDP and Ube/CDDP group. (C) CDDP-resistant GC cells were pre-stimulated with Ubenimex (0.2 mg/mL) and pEGFP-N1-CD13 or the combination of both for 24 h, and then treated with CDDP (20 μmol/L) for another 48h. Western blot assay was performed to determine CD13 expression. The representatives results (upper panels) and the means±SD of the relative expression (bottom panel) from three independent experiments were both demonstrated. **P< 0.01.