2.6. In vivo tumor xenograft model

A 100 µL suspension of 4 × 10⁶ BOY cells was combined with 100 µL Matrigel Matrix (Corning, Bedford, MA, USA). The mixture was used for subcutaneous injection into the sides of female nude mice (BALB/c nu/nu, 6‐ to 8‐week‐old). Mice were separated into four groups: vehicle, GC [gemcitabine 150 mg·kg⁻¹, intraperitoneal (i.p.) injection, days 7 and 14, cisplatin 6 mg·kg⁻¹, i.p., days 6 and 13], NCT‐503 (40 mg·kg⁻¹, 5 times a week 1 day after tumor injection), or the combination of GC and NCT‐503. The weight of each mouse was used to normalize the dose and the injection volume was < 150 μL. The tumor fraction was used to conduct terminal deoxynucleotidyltransferase‐mediated dUTP‐biotin nick end labeling (TUNEL). All the animal experiments were approved by the animal care review board of Kagoshima University (approval no. MD17047).