Concurrent delivery of GM-CSF and endostatin genes by a single adenoviral vector provides a synergistic effect on the treatment of orthotopic liver tumors.
BACKGROUND
The immune resistance of large tumors represents a major problem for cancer immunotherapy, whereas the need for repeated injections of high doses of recombinant anti-angiogenic proteins represents a similar problem for anti-angiogenic therapy. To test whether antitumor activity could be increased by combining the above two mechanisms, this study examined the therapeutic effect of combination gene therapy using a murine granulocyte-macrophage colony-stimulating factor (mGM-CSF) gene and a human endostatin (hED) gene on a rat orthotopic liver tumor model.


METHODS
An adenoviral vector was constructed that simultaneously carried two transcriptional cassettes, for the expression of mGM-CSF and hED, respectively, or that carried a single cassette of either gene. The adenoviruses were intratumorally administered to 3-day-old or 7-day-old tumors. Moreover, the antitumor effects of the combination therapy and monotherapy were assessed and compared.


RESULTS
The double-gene-containing adenoviral vector expressed transgenes as efficiently as the single-gene-containing vector. Moreover, the adenovirally expressed endostatin was biologically active, as demonstrated in vitro and in vivo. Results from animal experiments demonstrated a synergistic antitumor effect induced by the combined mGM-CSF and hED therapy. The combination of hED with mGM-CSF enhanced tumor-specific CTL activity, but did not interfere with the infiltration of cellular effectors in the tumor regions. The blood vessel density of the liver tumors markedly reduced as a result of hED expression in both monotherapy and combination therapy. Furthermore, combination therapy significantly increased the number of apoptotic cells in the tumor regions.


CONCLUSIONS
The experimental results suggest that the combined gene therapy against tumor cells and the tumor vascular system using antitumor immune mechanisms and anti-angiogenic mechanisms holds promise as a strategy for treating cancers.
Graduate Institute of Microbiology, National Taiwan University College of Medicine, Taipei 10016, Taiwan.
Kuo-Feng
KF
Tai
Pei-Jer
PJ
Chen
Ding-Shinn
DS
Chen
Lih-Hwa
LH
Hwang
D000256:Adenoviridae / Q000235:genetics*; D020533:Angiogenesis Inhibitors / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis; D015153:Blotting, Western; D002455:Cell Division; D002460:Cell Line; D045744:Cell Line, Tumor; D003094:Collagen / Q000494:pharmacology; D003131:Combined Modality Therapy; D004338:Drug Combinations; D043169:Endostatins / Q000235:genetics*; D042783:Endothelial Cells / Q000166:cytology; D004797:Enzyme-Linked Immunosorbent Assay; D018014:Gene Transfer Techniques; D015316:Genetic Therapy / Q000379:methods*; D005822:Genetic Vectors; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D007167:Immunotherapy / Q000379:methods*; D020287:In Situ Nick-End Labeling; D007797:Laminin / Q000494:pharmacology; D008099:Liver / Q000378:metabolism; D008113:Liver Neoplasms / Q000235:genetics* / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D008957:Models, Genetic; D009389:Neovascularization, Pathologic; D010957:Plasmids / Q000378:metabolism; D019408:Platelet Endothelial Cell Adhesion Molecule-1 / Q000096:biosynthesis; D011509:Proteoglycans / Q000494:pharmacology; D051381:Rats; D011916:Rats, Inbred F344; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013602:T-Lymphocytes, Cytotoxic / Q000378:metabolism; D013997:Time Factors; D014158:Transcription, Genetic; D019076:Transgenes
D020533:Angiogenesis Inhibitors; D004338:Drug Combinations; D043169:Endostatins; D007797:Laminin; D019408:Platelet Endothelial Cell Adhesion Molecule-1; D011509:Proteoglycans; C059485:matrigel; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D003094:Collagen