Autophagic Cell Death of Malignant Glioma Cells Induced by a Conditionally Replicating Adenovirus

• Published in: JNCI : Journal of the National Cancer Institute 2006-05, Vol.98 (9), p.625-636
• Main Authors: Ito, Hideaki, Aoki, Hiroshi, Kühnel, Florian, Kondo, Yasuko, Kubicka, Stefan, Wirth, Thomas, Iwado, Eiji, Iwamaru, Arifumi, Fujiwara, Keishi, Hess, Kenneth R., Lang, Frederick F., Sawaya, Raymond, Kondo, Seiji
• Format: Article
• Language: English
• Subjects: Adenoviridae; Adenovirus; Adenoviruses; Animals; Antineoplastic Agents - administration & dosage; Antineoplastic Agents - pharmacology; Autophagy - drug effects; Biological and medical sciences; Blotting, Western; Brain Neoplasms - drug therapy; Brain Neoplasms - physiopathology; Cancer; Cell Cycle; Cell death; Cell Line, Tumor; Cells; DNA-Binding Proteins - administration & dosage; DNA-Binding Proteins - pharmacology; Female; Fibroblasts; Glioma - drug therapy; Glioma - physiopathology; HeLa Cells; Humans; Injections, Intralesional; Medical sciences; Mice; Mice, Nude; Other treatments; Rodents; Telomerase - administration & dosage; Telomerase - pharmacology; Treatment. General aspects; Tumors; Uterine Cervical Neoplasms - drug therapy; Uterine Cervical Neoplasms - pathology
• ISSN: 0027-8874; 1460-2105
• DOI: 10.1093/jnci/djj161

Background: Conditionally replicating adenoviruses (CRAds) can be engineered to replicate selectively in cancer cells and cause cancer-specific cell lysis; thus they are considered a promising cancer therapy. Methods: To elucidate the mechanisms by which CRAds induce cancer-specific cell death, we infected normal human fibroblasts (MRC5, telomerase negative), human malignant glioma (U373-MG and U87-MG), human cervical cancer (HeLa), and human prostate cancer (PC3) cells (all telomerase positive) with CRAds regulated by the human telomerase reverse transcriptase promoter (hTERT-Ad) or control nonreplicating adenoviruses (Ad-GFP). Nonapoptotic autophagy was assessed in Ad-GFP- and hTERT-Ad–infected cells by examining cell morphology, the development of acidic vesicular organelles, and the conversion of microtubule-associated protein 1 light chain 3 from the cytoplasmic form to the autophagosome membrane form; signaling via mammalian target of rapamycin (mTOR), an autophagy-associated molecule, was monitored by western blot analysis. We also compared the growth of subcutaneous gliomas in nude mice that were treated by intratumoral injection with Ad-GFP or hTERT-Ad. Survival of athymic mice carrying intracranial gliomas treated by intratumoral injection with Ad-GFP or hTERT-Ad was compared by using the Kaplan–Meier method and the Cox–Mantel log-rank analysis. All statistical tests were two-sided. Results: hTERT-Ad induced tumor-specific autophagic cell death in tumor cells and in subcutaneous gliomas. hTERT-Ad–induced autophagy was associated with hTERT-Ad infection kinetics. The mTOR signaling pathway was suppressed in tumor cells and in subcutaneous gliomas treated with hTERT-Ad compared with GFP-Ad or no treatment as shown by reduced phosphorylation of mTOR's downstream target p70S6 kinase (p70S6K). hTERT-Ad treatment of mice (n = 7) slowed growth of subcutaneous gliomas (mean tumor volume = 39 mm3, 95% confidence interval [CI] = 23 to 54 mm3) compared with GFP-Ad treatment (n = 7) (mean tumor volume = 200 mm3, 95% CI = 149 to 251 mm3) at day 7 (volume difference = 161 mm3, 95% CI = 126 to 197 mm3; P