Docetaxel effect on tumorigenic C6 glioma cells is nitric oxide dependent. Free

B122

Dimethylarginine dimethylaminohydrolase (DDAH) is an enzyme that metabolises asymmetric dimethylarginine (ADMA), which is an endogenously produced inhibitor of nitric oxide synthase (NOS). DDAH is known to be a determinant of in vivo levels of ADMA. Activity of DDAH allows the production of nitric oxide. Nitric oxide is fast becoming known as an onco-preventative agent and a novel therapeutic to overcome tumour cell resistance. In this study, we examined the apoptotic effects of Docetaxel on a DDAH I over-expressing C6 glioma cell line (D27), compared with a mock-transfected (M8) control cell line. We show both apoptotic and non-apoptotic responses to Docetaxel. Cells were treated with Docetaxel (concentration determined from dose response) and tracked using timelapse microscopy. The cells were observed to undergo apoptosis and death was greater in D27 than in M8. Caspase activity assays on cells treated overnight showed activation of both caspase-2 and caspase-3 in D27 and M8. Activation of both caspases was higher in the D27 than M8. Hoechst 33342 staining of Docetaxel treated cells revealed a dramatic change in the morphology of the nuclei compared with the untreated controls. In vivo work was conducted on D27 and M8 tumours grown in MFI female athymic nude mice. Mice were treated with Docetaxel (administered via an i.p. injection). Growth delay studies and ¹H-MRS data acquisition were carried out before and after treatment. The post-treatment acquisitions were carried out 24 hours after drug administration. The growth delay studies did not show a difference in growth between the tumour types before and after treatment. However, the study of ¹H-MRS data showed a difference between M8 and D27. The M8 tumours appeared to be progressing, whereas the D27 tumours were not. We conclude that nitric oxide sensitises tumours to Docetaxel treatment. .