Chloroquine Enhances the Radiosensitivity of Bladder Cancer Cells by Inhibiting Autophagy and Activating Apoptosis.

Abstract

BACKGROUND/AIMS:

Chloroquine was formerly used as an anti-malarial agent drug but has now been proven to be useful for various diseases. This study aimed to investigate the radiosensitizing effect of chloroquine in bladder cancer, with an emphasis on autophagy inhibition and apoptosis induction.

METHODS:

Bladder cancer cell lines were irradiated with or without chloroquine. Cell proliferation was determined by a Cell Counting Kit 8 assay. The radiosensitization effect of chloroquine was evaluated by clonogenic survival and progression of xenograft tumors. Cell apoptosis was detected by flow cytometry and western blot. Radiation-induced DNA double strand break was measured by the staining of γ-H2AX. In addition, autophagy was detected by western blot, immunofluorescence staining, and electron microscopy.

RESULTS:

The treatment with chloroquine alone inhibited the proliferation of bladder cancer cells in a dose-dependent manner. Low cytotoxic concentrations of chloroquine enhanced the radiation sensitivity of bladder cancer cells with a sensitization enhancement ratio of 1.53 and 1.40. Chloroquine also obviously weakened the repair of radiation-induced DNA damage. A combination of radiation and chloroquine enhanced the apoptosis rate of EJ and T24 cells and down-regulated the expression of Bcl-2 while up-regulating the expression of caspase-3. Additionally, the relevant markers of autophagy were obviously increased in the combined group, meaning that chloroquine inhibited autophagy induced by irradiation. Furthermore, subcutaneous xenograft tumors displayed that the combination of radiation and chloroquine could impede tumorigenesis in vivo.

CONCLUSION:

In summary, these results provided support that by inhibiting autophagy and activating apoptosis, chloroquine might be a potentially promising radiosensitizer in the radiation therapy of bladder cancer.

• Authors: Feng Wang, Jinyuan Tang, Pengchao Li, Shuhui Si, Hao Yu, Xiao Yang, Jun Tao, Qiang Lv, Min Gu, Haiwei Yang, Zengjun Wang
• Journal: Cellular physiology and biochemistry : international journal of experimental cellular physiology, biochemistry, and pharmacology (Cell Physiol Biochem) Vol. 45 Issue 1 Pg. 54-66 ( 2018) ISSN: 1421-9778 [Electronic] Germany
• PMID: 29316551 (Publication Type: Journal Article)
• Copyright: © 2018 The Author(s). Published by S. Karger AG, Basel.

Chemical References

• Map1lc3b protein, mouse
• Microtubule-Associated Proteins
• Proto-Oncogene Proteins c-bcl-2
• Radiation-Sensitizing Agents
• Sequestosome-1 Protein
• Sqstm1 protein, mouse
• Chloroquine
• Caspase 3

Topics

• Animals
• Apoptosis (drug effects, radiation effects)
• Autophagy (drug effects, radiation effects)
• Caspase 3 (metabolism)
• Cell Line, Tumor
• Cell Proliferation (drug effects)
• Chloroquine (pharmacology)
• DNA Damage (drug effects, radiation effects)
• Down-Regulation (drug effects, radiation effects)
• Humans
• Mice
• Mice, Inbred BALB C
• Mice, Nude
• Microtubule-Associated Proteins (metabolism)
• Proto-Oncogene Proteins c-bcl-2 (genetics, metabolism)
• Radiation Tolerance (drug effects, radiation effects)
• Radiation, Ionizing
• Radiation-Sensitizing Agents (pharmacology)
• Sequestosome-1 Protein (metabolism)
• Up-Regulation (drug effects, radiation effects)
• Urinary Bladder Neoplasms (drug therapy, pathology, radiotherapy)