Glutathione S-transferases in normal and cancerous human colon tissue

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Abstract
In order to evaluate the role of the placental form of gluta thione S-transferase (GST-Pi) as a tumour marker, activity and composition of GSTs from human colon were investi gated. GSTs were purified from normal colon mucosa and from colomc tumours by affinity chromatography on gluta thione-agarose. After SDS-PAGE or isoelectric focusing these purified preparations revealed only one band that comigrated with GST-Pi from human placenta. A monoclonal antibody (mAb) very specific for GST-Pi was developed and characterized. On inimunoblot this mAb stains purified GST from normal and diseased colon tissue. GST activity was significantly higher in most cancerous (247 ± 38 nmoll mm/mg protein; n = 7), compared with the corresponding normal tissues (171 ± 18 nmol/min/mg protein; n = 7). In colon from patients without large bowel malignancies GST Pi is also by far the most prominent isoform detectable. In conclusion, both normal and tumorous colon tissue predominantly express GST-Pi and therefore GST-Pi is not suitable as a tumour marker for colonic carcinomas. However, the increased GST-Pi levels in colonic tumours could possibly contribute to the relatively high resistance to anti-cancer drugs.

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