Glutathione S-transferases in normal and cancerous human colon tissue

In order to evaluate the role of the placental form of glutathione S-transferase (GST-Pi) as a tumour marker, activity andcomposition of GSTs from human colon were investi gated. GSTswere purified from normal colon mucosa and from colomc tumoursby affinity chromatography on gluta thione-agarose. After SDS-PAGEor isoelectric focusing these purified preparations revealedonly one band that comigrated with GST-Pi from human placenta.A monoclonal antibody (mAb) very specific for GST-Pi was developedand characterized. On inimunoblot this mAb stains purified GSTfrom normal and diseased colon tissue. GST activity was significantlyhigher in most cancerous (247 ? 38 nmoll mm/mg protein; n =7), compared with the corresponding normal tissues (171 ? 18nmol/min/mg protein; n = 7). In colon from patients withoutlarge bowel malignancies GST Pi is also by far the most prominentisoform detectable. In conclusion, both normal and tumorouscolon tissue predominantly express GST-Pi and therefore GST-Piis not suitable as a tumour marker for colonic carcinomas. However,the increased GST-Pi levels in colonic tumours could possiblycontribute to the relatively high resistance to anti-cancerdrugs.