Suppression of human glioma growth by adenovirus-mediated Rb gene transfer.
OBJECTIVE
This study was conducted to obtain evidence that restoration of the retinoblastoma protein function may have therapeutic application for gliomas.


BACKGROUND
The development of glioblastoma multiforme involves progressive inactivation of several tumor suppressor genes. Abnormalities of the retinoblastoma tumor suppressor gene are found in the majority of cancers, including at least 30% of malignant gliomas. No final evidence has been produced about the role of Rb in suppressing glioma growth.


METHODS
To address this question, the Ad5CMV-Rb adenovirus carrying a 3.2-kb cDNA of the Rb gene was constructed. Expression of the exogenous protein was assessed by immunoblot and immunohistochemistry analyses. Growth curve assays were used to evaluate the effect of the Rb protein on glioma cell growth. Flow-cytometry analyses were used to analyze the phenotype of the cell cycle after the transfer of Rb. Human glioma xenografts implanted subcutaneously in nude mice were used for the tumorigenicity assay.


RESULTS
After the transfer of Rb, 80% of the treated cells expressed high levels of the retinoblastoma protein for at least 7 days. Within 5 days of treatment, the cells lost the neoplastic morphology and showed marked growth suppression. The majority of the Rb-expressing cells were arrested in the G1 phase of the cell cycle. In addition, the restoration of the retinoblastoma activity rendered the human glioma cells unable to form tumors in nude mice.


CONCLUSIONS
These findings provide direct evidence that inactivation of the retinoblastoma protein is a critical event in gliomas, and suggest that the restoration of wild-type retinoblastoma activity in these tumors may have therapeutic utility.
Fueyo
J
J
Department of Neuro-Oncology, The University of Texas M.D. Anderson Cancer Center, Houston 77030, USA.
Gomez-Manzano
C
C
Yung
W K
WK
Liu
T J
TJ
Alemany
R
R
Bruner
J M
JM
Chintala
S K
SK
Rao
J S
JS
Levin
V A
VA
Kyritsis
A P
AP
D000256:Adenoviridae / Q000235:genetics*; D000818:Animals; D002453:Cell Cycle / Q000502:physiology; D002455:Cell Division / Q000502:physiology; D018450:Disease Progression; D015972:Gene Expression Regulation, Neoplastic / Q000502:physiology; D018014:Gene Transfer Techniques; D016161:Genes, Retinoblastoma; D005822:Genetic Vectors; D005909:Glioblastoma / Q000628:therapy*; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D010766:Phosphorylation; D014183:Transplantation, Heterologous; D014407:Tumor Cells, Cultured