Serum gamma-glutamyltransferase and alkaline phosphatase during experimental liver metastases. Detection of tumour-specific isoforms and factors affecting their serum levels

Tumour-specific isoenzymes and tumour markers in serum are potentially usef ul in the detection and monitoring of liver metastases. An experimental rat model was used in the search for such isoenzymes and to study factors affe cting their serum levels. Splenic injection of CC531 colon carcinoma cells in syngeneic WagRij rats caused liver metastases after 3 weeks with concomi tant and significant increases in serum levels of gamma-glutamyltransferase (GT) and alkaline phosphatase (ALP). The presence of tumour-specific isofo rms of both enzymes, as well as increased amounts of the liver isoform of A LP, were demonstrated in serum. The serum levels of the tumour variants wer e clearly related to their elimination rates from the circulation. Thus, th e slow clearance of the tumour ALP resulted in high serum levels of this is oform, compared with the more rapid elimination of tumour GT and its lower serum level. When using another colon carcinoma cell Line (DHD/K12), metast atic to Liver in ED IX rats, no increases in serum GT were detected. This w as related to the rapid elimination fi om the circulation of the GT variant from the DHD/K12 metastatic tissue. The relatively high amount of the tumo ur ALP isoform detected in serum during growth of the CC531 liver metastase s indicated that this isoform could be useful as a marker of tumour growth. (C) 1998 Elsevier Science Ltd. AU rights reserved.