Temozolomide is the most commonly used chemotherapeutic agent in the therapy of GBM and is usually well-tolerated. It achieves its cytotoxic effect mainly by methylating the O6 position of guanine. Temozolomide displays its highest efficacy against tumors lacking MGMT expression.
The concomitant reduction in clonogenic ability, in the size of the CD133 population and in the growth kinetics of GBM cells indicates that BMP4 reduces the tumour-initiating cell pool of GBMs. BMP–BMPR signalling system—which controls the activity of normal brain stem cells—may also act as a key inhibitory regulator of tumour-initiating, stem-like cells from GBMs and the results also identify BMP4 as a novel, non-cytotoxic therapeutic effector, which may be used to prevent growth and recurrence of GBMs in humans.