Efficacy of systemically administered oncolytic vaccinia virotherapy for malignant gliomas is enhanced by combination therapy with rapamycin or cyclophosphamide.
OBJECTIVE
The oncolytic effects of a systemically delivered, replicating, double-deleted vaccinia virus has been previously shown for the treatment of many cancers, including colon, ovarian, and others. The purpose of this study was to investigate the oncolytic potential of double-deleted vaccinia virus alone or in combination with rapamycin or cyclophosphamide to treat malignant gliomas in vitro and in vivo.


METHODS
Rat (RG2, F98, C6) and human (A172, U87MG, U118) glioma cell lines were cultured in vitro and treated with live or UV-inactivated vaccinia virus. Viral gene [enhanced green fluorescent protein (EGFP)] expression by fluorescence-activated cell sorting, relative cell viability by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), and assays for cytopathic effects were examined. S.c. murine tumor xenografts (U87MG, U118, C6) and i.c. (RG2, F98) tumor models in immunocompetent rats were treated with systemic administration of EGFP-expressing vaccinia virus (vvDD-EGFP), alone or in combination with rapamycin or cyclophosphamide, or controls. Tumor size, viral biodistribution, and animal survival were assessed. Lastly, the oncolytic effects of vvDD-EGFP on human malignant glioma explants were evaluated.


RESULTS
vvDD-EGFP was able to infect and kill glioma cells in vitro. A single systemic dose of vvDD-EGFP significantly inhibited the growth of xenografts in athymic mice. Systemic delivery of vvDD-EGFP alone was able to target solitary and multifocal i.c. tumors and prolong survival of immunocompetent rats, whereas combination therapy with rapamycin or cyclophosphamide enhanced viral replication and further prolonged survival. Finally, vvDD-EGFP was able to infect and kill ex vivo primary human malignant gliomas.


CONCLUSIONS
These results suggest that vvDD-EGFP is a promising novel agent for human malignant glioma therapy, and in combination with immunosuppressive agents, may lead to prolonged survival from this disease.
Department of Oncology, Tom Baker Cancer Centre, Alberta, Canada.
Xue Qing
XQ
Lun
Ji-Hyun
JH
Jang
Nan
N
Tang
Helen
H
Deng
Renee
R
Head
John C
JC
Bell
David F
DF
Stojdl
Catherine L
CL
Nutt
Donna L
DL
Senger
Peter A
PA
Forsyth
J Andrea
JA
McCart
D000818:Animals; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use*; D045744:Cell Line, Tumor; D003131:Combined Modality Therapy; D003520:Cyclophosphamide / Q000627:therapeutic use*; D005260:Female; D005910:Glioma / Q000188:drug therapy / Q000628:therapy*; D006801:Humans; D007166:Immunosuppressive Agents / Q000627:therapeutic use*; D051379:Mice; D008819:Mice, Nude; D050130:Oncolytic Virotherapy; D051381:Rats; D020123:Sirolimus / Q000627:therapeutic use*; D014616:Vaccinia virus; D014779:Virus Replication / Q000187:drug effects
D007166:Immunosuppressive Agents; D003520:Cyclophosphamide; D020123:Sirolimus