Effect Of Temozolomide With Pyrimethamine Synergistic Combination Therapy On Cell Viability In Pituitary Gonadotroph Adenoma Cell Line

BackgroundCurrent therapy methods in pituitary adenoma include surgery, radiotherapy and medicine, none of which is perfect, especially when meeting some relapse aggressive pituitary adenomas. Temozolomide (TMZ) is an alkylating chemical therapic agent, which can cross the blood-brain barrier to treat glioma and other intracalvarium neoplasms. Currently, though the therapy of TMZ in pituitary adenoma is merely starting, there has been some resistant condition detected in some patients. It was reported that TMZ with pyrimethamine (PYR, a dihydrofolate reductase inhibitor) synergistic combination therapy could make the TMZ-resistant melanoma cells resensitive. If this synergistic combination therapy could be effective in some TMZ-resistant pituitary adenomas, it will be advancement in pituitary adenoma therapy.ObjectiveSearch the medicine overcoming TMZ-resistance of neoplasms when combined with TMZ. Demonstrate that when treating pituitary adenoma, TMZ with PYR combination therapy is able to enhance the cytotoxicity and the ability of anti-resistance of TMZ, then research its effective mechanism.MethodsCell cultivation; resistance cells Screening; Relative survival rate measuring with MTS assay; Death rate measuring with trypan blue staining; Cell circle statistics with flow cytometer and PI staining; Western Blot. Results and conclusions1This experiment demonstrated that when treating pituitary adenoma, TMZ with PYR combination therapy is able to enhance the cytotoxicity of TMZ. Considering the medicine character, PYR is a potential partner of TMZ in combination therapy in pituitary adenoma.2This experiment tried to screen the TMZ-resistant cells of mouse pituitary gonadotroph adenoma (αT3-1cell line) and got success. The cells screened could survive and generate in500umol/L TMZ, whose MGMT (one kind of antagonism protein of TMZ) increasing a little.3When treating this TMZ-resistant cell line, the synergistic effect of TMZ+PYR combination was more significant than normal cell line, implying that PYR could enhance the ability of anti-resistance of TMZ. In clinic, if some pituitary adenoma is resistant to TMZ treatment, we can try to add PYR to carry out the combination therapy.4This experiment validated the TMZ’s effect of DNA strand breaks (DSB), apoptosis advancing and G2cell circle arrest, which was consistent with its theory mechanism. It was also validated that the PYR’s effect of DSB, apoptosis advancing and S cell circle arrest, which was demonstrated due to the PYR’s effect of anti-folate.5The synergistic effect of TMZ+PYR combination therapy is probably due to the effect of "overlap attack".6The synergistic effect of TMZ+PYR combination therapy isn’t implemented by regulating the expressing of MGMT, adding PYR cannot change the MGMT quantity in treated cells.