title: Different involvement of autophagy in human malignant glioma cell lines undergoing irradiation and temozolomide combined treatments.
abstract: Glioblastoma (GB) has a poor prognosis, despite current multimodality treatment. Beside surgical resection, adjuvant ionizing radiation (IR) combined with Temozolomide (TMZ) drug administration is the standard therapy for GB. This currently combined radio-chemotherapy treatment resulted in glial tumor cell death induction, whose main molecular death pathways are still not completely deciphered. In this study, the autophagy process was investigated, and in vitro modulated, in two different GB cell lines, T98G and U373MG (known to differ in their radiosensitivity), after IR or combined IR/TMZ treatments. T98G cells showed a high radiosensitivity (especially at low and intermediate doses), associated with autophagy activation, assessed by Beclin-1 and Atg-5 expression increase, LC3-I to LC3-II conversion and LC3B-GFP accumulation in autophagosomes of irradiated cells; differently, U373MG cells resulted less radiosensitive. Autophagy inhibition, using siRNA against BECN1 or ATG-7 genes, totally prevented decrease in viability after both IR and IR/TMZ treatments in the radiosensitive T98G cells, confirming the autophagy involvement in the cytotoxicity of these cells after the current GB treatment, contrary to U373MG cells. However, rapamycin-mediated autophagy, that further radiosensitized T98G, was able to promote radiosensitivty also in U373MG cells, suggesting a role of autophagy process in enhancing radiosensitivity. Taken together, these results might enforce the concept that autophagy-associated cell death might constitute a possible adjuvant therapeutic strategy to enhance the conventional GB treatment.
authors.affiliation: Department of Genetics and Microbiology, University of Pavia, Pavia, Italy. silvia.palumbo@unipv.it
authors.forename: Silvia
authors.initials: S
authors.lastname: Palumbo
authors.forename: Luigi
authors.initials: L
authors.lastname: Pirtoli
authors.forename: Paolo
authors.initials: P
authors.lastname: Tini
authors.forename: Gabriele
authors.initials: G
authors.lastname: Cevenini
authors.forename: Francesco
authors.initials: F
authors.lastname: Calderaro
authors.forename: Marzia
authors.initials: M
authors.lastname: Toscano
authors.forename: Clelia
authors.initials: C
authors.lastname: Miracco
authors.forename: Sergio
authors.initials: S
authors.lastname: Comincini
mesh_terms: D051017:Apoptosis Regulatory Proteins / Q000096:biosynthesis / Q000235:genetics; D001343:Autophagy; D000071187:Autophagy-Related Protein 5; D000071186:Beclin-1; D001932:Brain Neoplasms / Q000188:drug therapy / Q000532:radiotherapy; D045744:Cell Line, Tumor; D002470:Cell Survival; D003131:Combined Modality Therapy; D003606:Dacarbazine / Q000031:analogs & derivatives* / Q000494:pharmacology; D005909:Glioblastoma / Q000188:drug therapy* / Q000532:radiotherapy*; D006801:Humans; D008565:Membrane Proteins / Q000096:biosynthesis / Q000235:genetics; D008869:Microtubule-Associated Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D034622:RNA Interference; D034741:RNA, Small Interfering; D011838:Radiation-Sensitizing Agents / Q000494:pharmacology; D020123:Sirolimus / Q000494:pharmacology; D000077204:Temozolomide
chemical_list: C502778:ATG5 protein, human; D051017:Apoptosis Regulatory Proteins; D000071187:Autophagy-Related Protein 5; C491997:BECN1 protein, human; D000071186:Beclin-1; C477012:MAP1LC3A protein, human; D008565:Membrane Proteins; D008869:Microtubule-Associated Proteins; D034741:RNA, Small Interfering; D011838:Radiation-Sensitizing Agents; D003606:Dacarbazine; D020123:Sirolimus; D000077204:Temozolomide