GSTP1 and neoplasm: Thus, long-term treatment (for up to 16 months) of rats with the DC has been demonstrated to inhibit not only DEN-induced GST-P expression, but also the carcinogen-mediated development of overt tumours (OT) and histopathological changes leading to tumour development (HT) as assessed both by visual observations and by microscopic examination of liver sections stained with H&E, Sweet's silver stain and the PAS stain for glycogen.