Although these results need to be confirmed in larger series as well as under different treatment conditions, our retrospective study shows clear evidence that p15 methylation is an important prognostic factor for survival and underlines that this tumor suppressor, involved in cell cycle control, is an attractive candidate for therapeutic approaches in glioblastomas.
As a whole, the data assign a tumor suppressor role to p15 and confirm homozygous deletions as the favorite mechanism for the inactivation of MTS1 and MTS2 in glioblastomas.
Our results indicate that loss of the p16 and p15 genes may be involved in tumor progression in human gliomas, especially in the development of glioblastoma, that this loss may give growth advantage to the cells in culture, and that it is not the result of culture artifacts.