Quantification of the cell-cycle inhibitors p27Kip1 and p21Cip1 in human atherectomy specimens: Primary stenosis versus restenosis

Abstract

Proliferation, a key determinator of vascular proliferative diseases, is dependent on cyclin/cyclin-dependent kinase (CDK) complexes, which are controlled by cyclin-dependent kinase inhibitors (CKIs) such as p27Kip1 and p21Cip1. Both have prognostic significance in various human malignancies. We have determined the levels of p27Kip1 and p21Cip1 in human directional coronary atherectomy specimens of primary lesions (n = 15) and lesions of in-stent restenosis (n = 18) in comparison to those of other vascular regions and have correlated CKI levels with clinical data. Quantitative immunoblotting demonstrated low expression of p27Kip1 in primary lesions (5.9 ± 0.5 ng/mg protein) compared with that in aorta (14.9 ± 0.9 ng/mg), internal mammary artery (16.7 ± 1.1 ng/mg), and carotid artery thrombendarterectomy specimens (16.5 ± 1.7 ng/mg). Similarly, p27Kip1 levels in lesions of in-stent restenosis were found to be significantly reduced (6.3 ± 1.1 ng/mg; mean time of restenosis development 367 ± 61 days). p27Kip1 levels did, however, not have prognostic significance for the development of restenosis, and expression levels of proliferating cell nuclear antigen and CDK2 were similar in all groups examined, indicating low proliferative activity. Clinically, p27Kip1 was not of value in predicting the development of restenosis. Furthermore, p27Kip1 tissue levels were not increased in statin-treated patients, implying that the favorable effect of these drugs is not a result of p27Kip1 stabilization. However, the relative content of p21Cip1 was found to be significantly up-regulated in restenosis compared with that in primary lesions (225%) and the other vascular regions. Our data imply that negative-feedback mechanisms are still intact in coronary proliferative disease, thereby contrasting the finding of deregulated proliferation in malignancies. (J Lab Clin Med 2003;141:179-89)