Data from p27<sup>Kip1</sup> expression inhibits glioblastoma growth, invasion, and tumor-induced neoangiogenesis

The tumor suppressor gene CDKN1B encodes for a 27-kDa cyclin-dependent kinase inhibitory protein, p27^Kip1, which together with its well-established role in the inhibition of cell proliferation, displays additional activities in the control of gene transcription and cell motility. p27^Kip1 thus represents a good candidate for a gene therapy approach, especially in those cancers refractory to the conventional therapies, like human glioblastoma. Here, we show that overexpression of p27^Kip1 in glioblastoma cell lines induced cell cycle arrest and inhibition of cell motility through extracellular matrix substrates. The use of adenoviral vectors in the treatment of glioblastoma in vivo showed that p27^Kip1 was able to block not only cancer cell growth but also local invasion and tumor-induced neoangiogenesis. The latter effect was due to the ability of p27 to impair both endothelial cell growth and motility, thus preventing proper vessel formation in the tumor. The block of neoangiogenesis depended on cytoplasmic p27^Kip1 antimigratory activity and was linked to its ability to bind to and inhibit the microtubule-destabilizing protein stathmin. Our work provides the first evidence that a successful p27^Kip1-based gene therapy is linked to tumor microenvironment modification, thus opening new perspectives to the use of gene therapy approaches for the treatment of refractory cancers. [Mol Cancer Ther 2008;7(5):1164–75]