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Potent antitumor activity of the combination of HSV-TK and endostatin by adeno-associated virus vector for bladder cancer in vivo.

BACKGROUND
Gene therapy may offer a new tool for the treatment of bladder cancer. Previously, we have shown a significant antitumor effect in bladder cancer xenografts in a nude mouse model using intratumoral herpes simplex virus thymidine (HSV-TK) and endostatin gene monotherapy.


METHODS
Given the high vascularity of human bladder cancer and the ability of HSV-TK or endostatin monotherapy to eradicate the tumors, we decided to test a novel combination of cytotoxic and antiangiogenic gene therapy using intratumorally delivered HSV-TK and endostatin adeno-associated viruses (AAV). We constructed plasmid AAV-TK-IRES-Endostatin (pAAV-TIE) and packaged the AAV particles containing gene fragments of HSV-TK and endostatin. The combined anticancer effect of recombinant AAV-TIE (rAAV-TIE) was measured in vivo with rAAV-HSV-TK and rAAV-Endostatin as the control groups.


RESULTS
The inverted terminal repeat sequence was amplified using only one primer and the fragment between two ITRs of pAAV-TIE measuring about 4 kb, which indicated a stable sequence of pAAV-TIE. Three clear bands representing the AAV capsid proteins VP1, VP2, and VP3 could be seen on both lanes against a very low background, which demonstrated that chloroform extraction could effectively extract contaminants from rAAV stock without significant loss of the rAAV. In vivo, our results showed that the tumors in mice injected with the rAAV-TIE not only took significantly longer to emerge but also that their growth, once established, was significant slower than that of tumors grown with single HSV-TK or endostatin treated animals.


CONCLUSIONS
We concluded that the inhibition of angiogenesis using endostatin gene transfer, together with the cytotoxic HSV-TK gene therapy, resulted in a significant antitumor effect compared to the single gene based therapy in BTCC.