Initial velocities in situ of G6PDH and PGDH and expression of proliferating cell nuclear antigen (PCNA): sensitive diagnostic markers of environmentally induced hepatocellular carcinogenesis in a marine flatfish ( Platichthys flesus L.)

Abstract

Flounder ( Platichthys flesus L.) were sampled in areas of relatively low contamination, in the open sea, and in a region at the mouth of the highly contaminated river Elbe (Germany). Prognostic and diagnostic values of the in situ reaction velocities of glucose 6-phosphate dehydrogenase (G6PDH) and phosphogluconate dehydrogenase (PGDH) inside and outside altered hepatocellular foci and carcinomas were demonstrated histochemically. Reactions were monitored quantitatively in time using image analysis. Expression of proliferating cell nuclear antigen (PCNA) was detected in serial sections as a marker for cell proliferation using the immunogold-silver labelling technique. Enzymic parameters were correlated with PCNA expression and histopathology. A large variety of foci and tumours were found in the livers of fish from the contaminated area. Histopathological classification could only indicate tendencies with respect to diagnosis and prognosis. However, in all stages of carcinogenesis, from early foci to well-organized trabecular basophilic tumours and anaplastic carcinomas, significantly higher initial velocities of G6PDH but not of PGDH and a higher PCNA labelling index (43–65%) were found in altered hepatocytes in comparison with surrounding extrafocal tissue. Furthermore, the increased capacities of G6PDH and PGDH in basophilic foci and nodules were found to be useful prognostic parameters. Significantly increased PCNA expression in small satellites of carcinomas reflected their malignancy and was used to differentiate between early foci and invasive protrusions of carcinomas. It is concluded that G6PDH activity and PCNA expression are very useful as diagnostic and prognostic tools to detect early preneoplastic lesions and to analyse progression towards carcinomas in environmental monitoring.