Glioma Regression In vitro and In vivo by a Suicide Combined Treatment

Abstract

We present here a suicide therapy against malignant gliomas based on the transfer to tumor cells of a gene encoding a B-glucosidase, linamarase (lis), which in the presence of the innocuous substrate linamarin (lin) produces cyanide, blocking the mitochondrial respiratory chain. Dog glioma cells carrying the lis gene are thus sensitive to lin (IC 50 of 250 Mg/mL at 48 hours) and cell death is accompanied by mitochondrial fission and ATP depletion. The combination of lis/lin with an otherwise nontoxic level of glucose oxidase (GO) enhances the therapeutic potential (IC 50 of 50 Mg/mL at 48 hours). GO produces hydrogen peroxide, inducing oxidative damage and increasing cellular stress. We show here the antitumoral effect of the lis/lin/GO therapy in a canine glioma cell line and in a xenograft glioma model in nude mice. The synergic combination causes mitochondrial membrane depolarization and phosphatidylserine externalization and accelerates death by 48 hours. The lethal process is caspase independent; poly(ADP-ribose) polymerase 1 is not implicated; and there is no apoptosis-inducing factor translocation to the nucleus. The combined system induces autophagic cell death that can be rescued by 3-methyladenine and is characterized by the presence of double-membrane vesicles and punctate

Advances in Diagnostic and Treatment Modalities for Intracranial Tumors

“…Common therapeutic strategies include suicide gene therapy, oncolytic treatment, immunomodultion, gene replacement, proapoptotic treatment, and antiangiogenesis 175, 203. Successful delivery or efficacy of gene therapy approaches using viral vectors and plasmid DNA has been shown experimentally in canine brain tumor cells and brain using adenoviral,204, 205, 206, 207, 208, 209 retroviral201, 202, 210 herpes,211 and adeno‐associated viral212, 213, 214 delivery. Few viral therapies have progressed to phase III clinical trials, and none have been shown to have significant efficacy in high‐grade brain tumors in phase III trials to date 175…”

Oncogene-mediated tumor transformation sensitizes cells to autophagy induction

“…Thus, tumor cells are sensitive to the blockage of autophagy (14,21) as well as to its stimulation (22)(23)(24). It has been previously demonstrated that autophagy is necessary for activated Ras-mediated transformation (7).…”

Therapy mediated by mitophagy abrogates tumor progression

“…11 We have previously applied a suicide therapy against malignant dog glioma cells based on the transfer to tumor cells of a gene encoding a β-glucosidase, linamarase (lis), which, in the presence of the innocuous substrate linamarin (lin), inhibits the electron transport chain by the generation of cyanide that blocks the complex IV producing oxidative stress that increases the generation of autophagic vacuoles. 12 This block also disrupts the filamentous pattern of mitochondria, facilitating the engulfment of these damaged organelles by the generated autophagosomes. 12,13 The lis/lin system is combined with glucose oxidase (GO), which transforms glucose to gluconic acid and hydrogen peroxide, raising even more the oxidative stress and the generation of autophagic vesicles that in turn increases the efficiency of the lis/lin lethal effect.…”

“…12 This block also disrupts the filamentous pattern of mitochondria, facilitating the engulfment of these damaged organelles by the generated autophagosomes. 12,13 The lis/lin system is combined with glucose oxidase (GO), which transforms glucose to gluconic acid and hydrogen peroxide, raising even more the oxidative stress and the generation of autophagic vesicles that in turn increases the efficiency of the lis/lin lethal effect.…”

“…23 The lis/lin/GO system, which combines cyanide production with oxidative stress, appears to be a potent autophagic death inducer, showing a great potential to abrogate the growth of aggressive tumors. 12,13 One of the most important aspects of this therapy is the associated bystander effect, because both cyanide and hydrogen peroxide are highly diffusible molecules that can cross cell membranes. 17 The lis/lin/GO associated death mechanism revealed important damage to mitochondria in the absence of caspase activation.…”