Efficacy of clinically relevant temozolomide dosing schemes in glioblastoma cancer stem cell lines (original) (raw)

2012, Journal of Neuro-Oncology

The effectiveness of temozolomide (TMZ) dosing schemes and the ''rechallenge'' of recurrent glioblastoma (GBM) with TMZ are controversial. We therefore compared the efficacy of different TMZ dosing schemes against GBM cancer stem cell (CSC) lines in vitro. In O 6 -methyl-guanidine-methyl-transferase (MGMT)-negative CSC lines, all schedules (1 day on/27 days off, 5 days on/23 days off, 7 days on/7 days off, 21 days on/7 days off, continuous lowdose TMZ) depleted clonogenic cells. In TMZ-resistant CSC lines, the 7 days on/7 days off scheme showed higher toxicity as compared with the other schemes. However, clinically feasible concentrations remained ineffective in highly resistant CSC lines. In addition, none of the schedules induced long-term depletion of clonogenic cells even at the highest concentrations (up to 250 lM). After sublethal TMZ treatment for 5 days, TMZ rechallenge of recovering CSC lines remained effective. Our data advocate CSC lines as in vitro model to address clinical questions. Using this model, our data suggest the effectiveness of TMZ in MGMT-negative CSC lines and support the concept of TMZ rechallenge.