Antitumoral efficacy and neurotoxic profile of adenoviral vectors encoding proapoptotic genes to be used in combination with Flt3L for immunotherapy against glioblastoma.

CANDOLFI; MUHAMMAD; PUNTEL; LIU; KROEGER; MONDKAR; LERNER; LEE; FOULAD; KING; KATSUATI; LOWENSTEIN; CASTRO

Boston, Massachusetts, USA

Congreso; American Society of Gene Therapy; 2008

Antitumoral efficacy and neurotoxic profile of adenoviral vectors encoding proapoptotic transgenes and Flt3L for immunotherapy against glioblastomaMarianela Candolfi1, Gwen D King1, AKM G Muhammad1, Mariana Puntel1, Kurt M Kroeger1, Chunyan Liu1, G , Gabrielle E Ahlsadeh1, Jonathan Lerner1, Sharon Lee1, David Foulad1, Katsuaki Sato2, Pedro R Lowenstein1, Maria G Castro1.1 Gene Therapeutics Research Institute, Cedars-Sinai Medical Center, Department of Medicine and Department of Molecular and Medical Pharmacology, David Geffen School of Medicine, University of California Los Angeles, 8700 Beverly Blvd., Davis Bldg., Room 5090, Los Angeles, CA 90048.2 Laboratory for Dendritic Cell Immunobiology, Research Center for Allergy and Immunology, RIKEN Yokohama Institute, Kanagawa, JapanGlioblastoma Multiforme (GBM) is the most common subtype of primary brain tumor in adults, and its prognosis is dismal. We assessed the efficacy and neurotoxicity of adenoviruses (Ads) expressing proapoptotic transgenes, i.e. HSV1-thymidine kinase (Ad-TK), TNF-α (Ad-TNF-α), FasL (Ad-FasL) or TRAIL (Ad-TRAIL) for GBM immunotherapy in combination with the immuno-stimulant Flt3L (Ad-Flt3L). TK selectively kills rapidly dividing cells in combination with the prodrug ganciclovir (GCV), while TNF-α, FasL or TRAIL kill cells expressing the respective death receptor. Rats bearing intracranial CNS-1 tumors were injected intratumorally with the Ads expressing the proapoptotic transgenes 4 days after tumor implantation. We found that while rats bearing small tumors treated with saline, Ad-TNF-α and Ad-TRAIL succumbed due to tumor burden, Ad-TK and Ad-FasL inhibited tumor progression, and significantly improved the survival of the rats. However, when we used Ad-TK or Ad-FasL to treat larger tumors (day 9 after implantation), we found that they are ineffective to improve survival. Less than 20% of rats treated with Ad-TK survived long term and none of the rats treated with Ad-FasL rats survived further than the saline group. Thus, we used the combination of Ad-TK or Ad-FasL with Ad-Flt3L which were injected intratumorally in rats bearing large tumors. Flt3L recruits and activates dendritic cells into the brain, improving antigen presentation. We found that although Ad-Flt3L poorly improved the survival of Ad-FasL-treated rats, it significantly increased survival when combined with Ad-TK; >60% of long term survivors. The neuropathological analysis of naïve rat brains injected with these proapoptic viruses demonstrated that expression of FasL and TRAIL caused overt toxicity, leading to profuse infiltration of inflammatory cells, reduction in TH expression in the striatum, local hemorrhages and ventriculomegaly, while administration of Ad-TK did not significantly alter the structure of the normal brain and induced only a mild, transient local inflammation. Our results show that the combination therapy, Ad-Flt3L/Ad-TK plus GCV is the most efficient amongst the several proapoptotic approaches tested. Moreover, while intracranial delivery ofnon-specific proapoptotic cytokines like TRAIL and FasL is very toxic to the normal brain, administration of Ad-TK does not induce overt neuropathological side effects. Our results warrant further development of this combination therapy for the future implementation of a clinical trial for GBM.Supported by NIH/NINDS R01 NS44556.01, R21-NSO54143.01; UO1 NS052465.01; RO3 TW006273-01 to M.G.C.; RO1 NS 054193.01; RO1 NS 42893.01; U54 NS045309-01, and R21 NS047298-01 to P.R.L; F32 NS058156.01 to M.C.