As presented in Figures 4B–E, p21 (p < 0.01 in HuCCT-1 and p < 0.0001 in CCLP-1) and p53 (p < 0.0001 in HuCCT-1 and p < 0.05 in CCLP-1) increased markedly, and a marked reduction was observed in cyclin E2 (p < 0.0001 in HuCCT-1 and p < 0.05 in CCLP-1), which indicated that treatment of HCQ with IC50 concentration might result in G1 arrest in cholangiocarcinoma cells. Here, CDKN1A is linked to cholangiocarcinoma.