The frequencies of hypermethylation for the 10 genes were as follows, in oligodendrogliomas and ependymomas, respectively: 80% and 28% for MGMT; 70% and 28% for GSTP1; 66% and 57% for DAPK; 44% and 28% for TP14(ARF); 39% and 0% for THBS1; 24% and 28% for TIMP3; 24% and 14% for TP73; 22% and 0% for TP16(INK4A); 3% and 14% for RB1; and 0% in both neoplasms for TP53.
The present results suggest that p73 and p21 overexpression of ependymomas and p21 overexpression of pilocytic astrocytomas are one of the features of these tumors, and that p73 overexpression does not influence the expression manners of either p21 or MDM2 in gliomas.
These observations suggest tissular or tumoral differences in the control of p73 gene transcription and alternative splicing, and raise the problem of the role of p73 isoforms in the control of tumor growth, particularly in ependymomas.