Chloroquine, an autophagy inhibitor, potentiates the radiosensitivity of glioma initiating cells by inhibiting autophagy and activating apoptosis

Abstract

BackgroundGlioblastoma is refractory to conventional treatment, which is combined of surgery, chemotherapy and radiotherapy. Recent studies have shown that glioma initiating cells (GICs) contribute to tumorigenesis and radioresistance. Recently, other studies showed that the GICs use the autophagy as the major pathway to survive. Chloroquine, an anti-malarial chemical, is an autophagic inhibitor which blocks autophagosome fusion with lysosome and slows down lysosomal acidification. The aim of this study was to explore the mechanisms of chloroquine on the radiosensitivity of GICs.MethodsHuman glioblastoma cell lines U87 were investigated. MTT and clonogenic survival assay were used to evaluate the cell viability and survival from radiation. The formation of autophagosomes were evaluated by immunofluorescence. Annexin V-FITC/PI staining and flow cytometry were used to quantify the apoptotic cells. The expression levels of proteins were analyzed by Western blot. Cell cycle status was analyzed by checking DNA content after staining with PI. A comet assay was used to assess the DNA repair in the cells. Tumorsphere assay was used for evaluating GICs’ renewal ability.ResultsTreatment of U87 GICs with chloroquine (10–80 nmol/L) alone inhibited the cell growth in a dose-dependent manner. A dose of chloroquine (20 nmol/L) obviously enhanced the radiation sensitivity of U87 GICs., we found more punctate patterns of microtubule-associated protein LC3 immunoreactivity in radiation-treated U87 GICs, and the level of membrane-bound LC3-II was obviously enhanced. A combination of radiation and chloroquine obviously enhanced the U87 GICs’ apoptosis, as demonstrated by the enhanced levels of caspase-3, and reduced level of Bcl-2. In additon, combination of radiation and chloroquine cause G1/G0 cell cycle arrest. what’s more, Chloroquine obviously weakened the repair of radiation-induced DNA damage as reflected by the tail length of the comet. Combination treatment of irradiation and chloroquine has synergistic effects on decreasing the GICs’ tumorsphere number and diameter.ConclusionChloroquine enhances the radiosensitivity of GICs in vitro, suggesting the feasibility of joint treatment with chloroquine with radiation for GBM.

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

“…After the chloroquine treatment, the number of LC3 II puncta also increased by immunofluorescence. Some studies have shown that chloroquine could be a potential radiation sensitizer by inhibiting autophagy [21, 29]. In the current study, we explored the radiosensitizing effects of chloroquine in bladder cancer in vitro and in vivo .…”

“…In addition, Golden et al [23] suggested that chloroquine blocked autophagy and triggered endoplasmic reticulum stress, thereby increasing the chemosensitivity of glioma cells to temozolomide. In addition, Ye et al [21] showed that chloroquine enhanced the radiosensitivity of glioma initiating cells. It is therefore of interest to elucidate the association between chloroquine and radiosensitivity in bladder cancer.…”

Consideration of Ketogenic Metabolic Therapy as a Complementary or Alternative Approach for Managing Breast Cancer

“…This could account, in part, for a better drug delivery to solid tumors under KMT. The antimalarial drug, chloroquine neutralizes lysosomal pH reducing phagocytosis and autophagy, and thus depriving invasive and metastatic tumor cells from obtaining glucose and glutamine (34,204,205). Chloroquine can also inhibit mitochondrial diaphorases that oxidize NADPH to NAD+, which in turn would reduce mSLP (46,206).…”

Dl‐3n‐butylphthalide improves traumatic brain injury recovery via inhibiting autophagy‐induced blood‐brain barrier disruption and cell apoptosis

“…In addition to its role in cellular homeostasis, autophagy also contributes to programmed cell death, 14 which can induced apoptosis via enhancing tumour necrosis factor-related apoptosis-inducing ligand (TRAIL). [16][17][18] Inhibition of autophagy activation is beneficial for BBB integrity in early stage in stroke. [16][17][18] Inhibition of autophagy activation is beneficial for BBB integrity in early stage in stroke.…”

“…15 A growing body of evidences indicate that autophagy is important for the functional recovery of several central nervous system (CNS) diseases. [16][17][18] Inhibition of autophagy activation is beneficial for BBB integrity in early stage in stroke. Enhanced autophagy by rapamycin (RAPA) further causes ZO-1 degradation and MMP-9 secretion after high glucose-induced damage.…”