Glioma
This group comprises anaplastic astrocytomas and glioblastoma multiforme. Whereas the median overall survival of anaplastic (WHO grade III) gliomas is approximately 3 years, glioblastoma multiforme has a poor median overall survival of c. 15 months.
Glioma
Epigenetic repression of DNA repair genes is often found in progression to sporadic glioblastoma. For instance, methylation of the DNA repair gene "MGMT" promoter was observed in 51% to 66% of glioblastoma specimens. In addition, in some glioblastomas, the MGMT protein is deficient due to another type of epigenetic alteration. MGMT protein expression may also be reduced due to increased levels of a microRNA that inhibits the ability of the "MGMT" messenger RNA to produce the MGMT protein. Zhang et al. found, in the glioblastomas without methylated "MGMT" promoters, that the level of microRNA miR-181d is inversely correlated with protein expression of MGMT and that the direct target of miR-181d is the "MGMT" mRNA 3’UTR (the three prime untranslated region of "MGMT" messenger RNA).