The p73 gene is able to encode transcriptionaly active TAp73, as well as a 
dominant-negatively acting DeltaNp73 transcript isoforms. We studied 
differential expression of these forms in normal brain as well as glial tumors, 
by semiquantitative RT-PCR. The expression of p73 was low or undetectable in 
normal brain tissues. Most of the tumors and non-tumor brain tissues also lacked 
significant expression of p73 in patients with low-grade astrocytomas. In 
contrast, most high-grade glial tumors displayed strong up-regulation of TAp73, 
whereas only a few displayed DeltaNp73 expression. These aberrations may reflect 
the inactivation of retinoblastoma pathway in these tumors which result in the 
activation of E2F transcription factors, since TAp73 is a known target of E2F1 
gene. The study of TAp73 expression in brain tumors may serve as a means to 
evaluate the retinoblastoma pathway-dependent tumor progression.