Resistance of colon cancer to 5-fluorouracil may be overcome by combination with chloroquine, an in vivo study

Anticancer Drugs. 2012 Aug;23(7):675-82. doi: 10.1097/CAD.0b013e328353f8c7.


Autophagy is a complex of adaptive cellular response that enhances cancer cell survival in the face of cellular stresses such as chemotherapy. Recently, chloroquine diphosphate (CQ), a widely used antimalarial drug, has been studied as a potential inhibitor of autophagy. Here, we aimed to investigate the role of CQ in potentiating the effect of 5-fluorouracil (5-FU), the chemotherapeutic agent of first choice for the treatment of colorectal cancer, in an animal model of colon cancer. The mouse colon cancer cell line colon26 was used. For the in-vivo study, colon26 cells were injected subcutaneously into BALB/c mice, which were treated with saline as a control, CQ (50 mg/kg/day), 5-FU (30 mg/kg/day), or the combination therapy (CQ plus 5-FU). The tumor volume ratio and body weight were monitored. After the sacrifice, tumor tissue protein extracts and tumor sections were prepared and subjected to immunoblotting for the analysis of autophagy-related and apoptosis-related proteins, and the terminal transferase uridyl end labeling assay. The combination of CQ resulted in the inhibition of 5-FU-induced autophagy and a significant enhancement in the 5-FU-induced inhibition of tumor growth. Furthermore, the combination treatment of CQ and 5-FU resulted in a significant increase in the ratio of apoptotic cells compared with other treatments. The expression levels of the proapoptotic proteins, namely Bad and Bax, were increased by the CQ treatment in the protein extracts from tumors. Our findings suggest that the combination therapy of CQ and 5-FU should be considered as an effective strategy for the treatment of colorectal cancer.

MeSH terms

  • Animals
  • Antimetabolites, Antineoplastic / administration & dosage
  • Antimetabolites, Antineoplastic / pharmacology
  • Antineoplastic Combined Chemotherapy Protocols / therapeutic use*
  • Apoptosis / drug effects
  • Autophagy / drug effects*
  • Cell Line, Tumor
  • Cell Proliferation / drug effects
  • Cell Survival / drug effects
  • Chloroquine / administration & dosage
  • Chloroquine / analogs & derivatives
  • Chloroquine / pharmacology
  • Colonic Neoplasms / drug therapy*
  • Colonic Neoplasms / pathology
  • Colorectal Neoplasms / drug therapy*
  • Colorectal Neoplasms / pathology
  • Drug Resistance, Neoplasm / drug effects*
  • Female
  • Fluorouracil / administration & dosage
  • Fluorouracil / pharmacology
  • Mice
  • Mice, Inbred BALB C
  • Microtubule-Associated Proteins / drug effects
  • Microtubule-Associated Proteins / metabolism
  • RNA Nucleotidyltransferases / drug effects
  • RNA Nucleotidyltransferases / metabolism
  • Transcription Factor TFIIH
  • Transcription Factors / drug effects
  • Transcription Factors / metabolism
  • Tumor Burden / drug effects*


  • Antimetabolites, Antineoplastic
  • Gtf2h1 protein, mouse
  • Map1lc3b protein, mouse
  • Microtubule-Associated Proteins
  • Transcription Factors
  • Transcription Factor TFIIH
  • chloroquine diphosphate
  • Chloroquine
  • RNA Nucleotidyltransferases
  • UTP-RNA uridylyltransferase
  • Fluorouracil