p27–p16 Chimera: A Superior Antiproliferative for the Prevention of Neointimal Hyperplasia

Abstract

Cyclin-dependent kinase inhibitors (CDKi's) may be useful to treat hyperproliferative vascular disorders, such as restenosis induced following angioplasty or vein engraftment. We have shown that a novel fusion protein of the CDKi's p27 and p16, named W9, significantly reduces proliferation of human coronary smooth muscle cells in vitro, by blocking cell proliferation without inducing apoptosis. We have now evaluated the efficacy of adenovirus-mediated gene transfer of W9 (AV-W9) in a balloon-injury model, in the carotid arteries of cholesterol-fed rabbits. We observed that intravascular delivery of 2 x 10(11) viral particles of AV-W9 3 days following balloon injury inhibited intimal hyperplasia by 60% compared to a control virus (P > 0.001). PCNA expression in the AV-W9-treated vessels, a marker of injury-induced cell proliferation, was also reduced compared to the control virus-treated vessels. Direct comparison of the efficacy of AV-W9 and AV-p16 and AV-p27 in this model indicated that delivery of either of the parental genes was significantly less effective in inhibiting intimal thickening compared to the AV-W9 treatment. We conclude that combining the activities of multiple cell cycle regulatory proteins greatly increases the potency of cytostatic gene therapy in the treatment of balloon injury-induced intimal hyperplasia and represents a promising potential approach to preventing postangioplasty restenosis.

p27-p16 Fusion Gene Inhibits Angioplasty-Induced Neointimal Hyperplasia and Coronary Artery Occlusion

“…AVs at high doses have been shown to mediate hepatocellular toxicity after vascular administration. We have observed in mice and rabbits 19 and Hackett et al 25 have observed in pigs that the majority of virus that is delivered to the vasculature ends up in secondary organs. In rodents the primary target is the liver followed by the lung, 19 and in pigs the reverse is the case.…”

“…We have observed in mice and rabbits 19 and Hackett et al 25 have observed in pigs that the majority of virus that is delivered to the vasculature ends up in secondary organs. In rodents the primary target is the liver followed by the lung, 19 and in pigs the reverse is the case. Hackett et al 25 have reported that administration of 10 12 vp of a first-generation AV to the coronary artery of 28-to 30-kg swine resulted in 74% of the vector going to the lung, 16% of the vector going to the liver, and Ϸ8% of the vector remaining in the heart.…”

“…18,19,21 Before testing the virus in pigs, we compared the impact of the AV-W9 virus to a control AV vector that encoded no transgene (AV-null). New Zealand White rabbit carotid arteries were balloon-injured and 3 days later exposed to 10 11 vp of AV-W9 or AV-null (Figure 1).…”

“…18 One chimeric CDKi, termed W9, was selected from a series of p27-p16 fusion molecules for further development because of its superior antiproliferative activity in vascular SMCs 18 and a rabbit carotid artery vascular injury model. 19 W9 comprises a severely truncated derivative of p27 (amino acids 25 to 93) fused to p16. To assess its potential utility in preventing coronary restenosis, 1ϫ10 12 viral particles (vp) of AV-W9 were delivered using the Cordis Crescendo catheter to porcine coronary arteries immediately after balloon injury.…”

Break the Cycle: The Role of Cell-Cycle Modulation in the Prevention of Vasculoproliferative Diseases

“…58 Another approach takes advantage of chimeras of CDKIs (p27-p16) that are thought to have a broader inhibitory effect on the CDK family members. 59 In fact, adenoviral-mediated overexpression of the p27-p16 chimera has a greater inhibitory effect on neointimal hyperplasia than either p27 or p16 alone when evaluated following balloon injury of the carotid arteries of cholesterol-fed rabbits. Early antisense approaches have also been used to halt proliferation by targeting both the synthetic machinery and mitotic checkpoint proteins.…”