There are at least four major DNA repair pathways that may go awry in GBMs, including nucleotide excision repair, base excision repair, mismatch repair, and direct reversal of lesions in recombination.23,24 As one example, elevated levels of the DNA repair enzyme O6-methylguanine-DNA methyltransferase (MGMT) have been demonstrated in GBM.25 This would confer resistance towards alkylating agents. The gene discussed is MGMT; the disease is glioblastoma.