Telomere 3′ overhang-specific DNA oligonucleotides induce autophagy in malignant glioma cells

Telomere 3' overhang-specific DNA oligonucleotides (T-oligos) induce cell death in cancer cells, presumably by mimicking telomere loop disruption. Therefore, T-oligos are considered an exciting new therapeutic strategy. The purpose of this study was to elucidate how T-oligos exert antitumor effects on human malignant glioma cells in vitro and in vivo. We demonstrated that T-oligos inhibited the proliferation of malignant glioma cells through induction of nonapoptotic cell death and mitochondria hyperpolarization, whereas normal astrocytes were resistant to T-oligos. Tumor cells treated with T-oligos developed features compatible with autophagy, with development of autophagic vacuoles and conversion of an autophagy-related protein, microtubule-associated protein 1 light chain 3 from type I ( cytoplasmic form) to type II ( membrane form of autophagic vacuoles). A reverse-phase protein microarray analysis and Western blotting revealed that treatment with T-oligos inhibited the mammalian target of the rapamycin ( mTOR) and the signal transducer and activator of transcription 3 (STAT3). Moreover, pretreatment with T-oligos significantly prolonged the survival time of mice inoculated intracranially with malignant glioma cells compared with that of untreated mice and those treated with control oligonucleotides ( P = 0.0065 and P = 0.043, respectively). These results indicate that T-oligos stimulate the induction of nonapoptotic autophagic also known as type II programmed cell death and are thus promising in the treatment of malignant glioma.-Aoki, H., Iwado, E., Eller, M. S., Kondo, Y., Fujiwara, K., Li, G.-Z., Hess, K. R., Siwak, D. R., Sawaya, R., Mills, G. B., Gilchrest, B. A., Kondo, S. Telomere 3' overhang-specific DNA oligonucleotides induce autophagy in malignant glioma cells.