Preclinical characterization of the antiglioma activity of a tropism-enhanced adenovirus targeted to the retinoblastoma pathway.
BACKGROUND
Oncolytic adenoviruses are promising therapies for the treatment of gliomas. However, untargeted viral replication and the paucity of coxsackie-adenovirus receptors (CARs) on tumor cells are major stumbling blocks for adenovirus-based treatment. We studied the antiglioma activity of the tumor-selective Delta-24 adenovirus, which encompasses an early 1 A adenoviral (E1A) deletion in the retinoblastoma (Rb) protein-binding region, and of the Delta-24-RGD adenovirus. Delta-24-RGD has an RGD-4C peptide motif inserted into the adenoviral fiber, which allows the adenovirus to anchor directly to integrins.


METHODS
CAR and integrin expression were examined by flow cytometry in six glioma cell lines and in normal human astrocytes (NHAs). Adenoviral vectors containing green fluorescent protein (GFP) (AdGFP and AdGFP-RGD) were used to infect glioma cell lines with high or low CAR expression. Viability of glioma cells infected with different adenoviruses was assessed by trypan blue staining. Adenovirus replication was quantified with the infection-dose replication assay. Athymic mice carrying glioma xenografts received intratumoral injections of Delta-24-RGD or Delta-24 and were followed for survival, which was analyzed by the Kaplan-Meier method and the log-rank test. All statistical tests were two-sided.


RESULTS
Half the glioma cell lines expressed low levels of CAR (defined as <50% of cells expressing detectable CAR); all lines expressed integrins in more than 50% of cells. Infection of U-87 MG cells (a low-CAR-expressing line) with AdGFP-RGD resulted in approximately six times more GFP-positive cells than infection with AdGFP. Delta-24-RGD was more cytopathic to both low- and high-CAR-expressing glioma lines than Delta-24, and it replicated more efficiently in both cell lines. In the xenografted mice, intratumoral injection of Delta-24-RGD was associated with longer survival than intratumoral injection of Delta-24 (P<.001, log-rank test). Furthermore, 60% of Delta-24-RGD-treated mice but only 15% of Delta-24-treated mice survived more than 4 months (difference = 45%, 95% CI = 21% to 68%).


CONCLUSIONS
The antitumor activity of Delta-24-RGD suggests that it has the potential to be an effective agent in the treatment of gliomas.
Fueyo
Juan
J
Department of Neuro-Oncology, University of Texas M. D. Anderson Cancer Center, Houston, TX 77030, USA. jfueyo@mdanderson.org
Alemany
Ramon
R
Gomez-Manzano
Candelaria
C
Fuller
Gregory N
GN
Khan
Asadullah
A
Conrad
Charles A
CA
Liu
Ta-Jen
TJ
Jiang
Hong
H
Lemoine
Michael G
MG
Suzuki
Kaori
K
Sawaya
Raymond
R
Curiel
David T
DT
Yung
W K Alfred
WK
Lang
Frederick F
FF
D000256:Adenoviridae; D000818:Animals; D000951:Antigens, Neoplasm / Q000032:analysis*; D001253:Astrocytes / Q000276:immunology; D014408:Biomarkers, Tumor / Q000032:analysis*; D001932:Brain Neoplasms / Q000188:drug therapy / Q000276:immunology / Q000473:pathology / Q000532:radiotherapy / Q000628:therapy*; D002135:Calcium-Binding Proteins / Q000032:analysis*; D004396:Coloring Agents; D005136:Eye Proteins; D005434:Flow Cytometry; D005456:Fluorescent Dyes; D015972:Gene Expression Regulation, Neoplastic; D005910:Glioma / Q000188:drug therapy / Q000276:immunology / Q000473:pathology / Q000532:radiotherapy / Q000628:therapy*; D051597:Hippocalcin; D006801:Humans; D007150:Immunohistochemistry; D015552:Injections, Intralesional; D016023:Integrins / Q000032:analysis; D008074:Lipoproteins; D051379:Mice; D008819:Mice, Nude; D009419:Nerve Tissue Proteins; D051603:Recoverin; D012175:Retinoblastoma; D014183:Transplantation, Heterologous; D014343:Trypan Blue; D014407:Tumor Cells, Cultured
D000951:Antigens, Neoplasm; D014408:Biomarkers, Tumor; D002135:Calcium-Binding Proteins; D004396:Coloring Agents; D005136:Eye Proteins; D005456:Fluorescent Dyes; D016023:Integrins; D008074:Lipoproteins; D009419:Nerve Tissue Proteins; C496731:RCVRN protein, human; C496732:Rcvrn protein, mouse; D051603:Recoverin; D051597:Hippocalcin; D014343:Trypan Blue