2,5-dimethyl-celecoxib (DMC) is a close structural analog of the selective cyclooxygenase-2 (COX-2) inhibitor celecoxib (Celebrex®) that lacks COX-2 inhibitory function yet maintains all of celecoxibs anti-tumor properties. We set out to investigate the potential of combining current glioblastoma chemotherapies with DMC as a new approach to enhance glioblastoma cell killing. DMC was not only able to enhance tumor cell killing when combined with other drugs but also induced glioblastoma growth arrest and apoptosis in low glucose and hypoxic conditions which are normally associated with chemoresistance. Therefore, if DMC were used in combination it may potentially be able to reverse this chemoresistance and restore or even enhance these drugs inhibitory effects.
In addition, we also discovered inconsistencies between the MTT assay and other in vitro cell growth and survival assays. Hence, the MTT assay should be used with caution, and its results should be supported by other available in vitro assays.