PP-26 Serum enzyme activities in monitoring melim melanoma progression and regression.

Objectives of the study: To evaluate whether serum enzyme activities reflect both tumour progression and regression in a hereditary melanoma minipig MeLiM model /Cell mol Biol 45,1999,1119/ and to compare the enzyme profiles with those in murine melanomas and human disease. Material and methods: Tyrosinase activity was measured by a dopa oxidase method /Neoplasma 28,1981,59/, γ -glutamyltransferase (GGT) was monitored by means of the GGT100 set/Lachema, Czech Rep./ and neuron-specific enolase /NSE/ was analyzed with a radioimmunoassay kit /Cis-Bio Int., France/ in sera of minipigs with localized/n = 35/, metastatic /n = 22/ and cryptogenic /n = 14/ melanomas and also in animals with a spontaneous melanoma regression/n = 13/ or regression induced by devitalization therapy/n = 44/ and in control minipigs /n = 36/. Data were statistically analyzed by the Student's t -test. Results: A significant increase in tyrosinase activity (P < 0.05) was found not only in the group of animals with cryptogenic melanoma, but also in animals with spontaneous and experimentally induced melanoma regression, probably due to a better enzyme release from tumour cells. Similar results were obtained as for the GGT: There was a significant increase of activity in the groups of minipigs with regressing melanomas. NSE in experimental melanoma models has not yet been studied. The upper physiological NSE limit in minipigs (deduced as x + 2σ = 18 ng/ml) was overcome in 8 of 54 sera = in 18% of minipigs in advanced stage of melanoma progression. Conclusions: Our results document that enzyme profiles in melanoma-bearing minipigs faithfully resemble those in human counterpart (i.e. serum enzyme activities begin to be of marker value only in later stages) demonstrating that the MeLiM model is close to human melanoma unlike murine melanoma models, in which a steep increase of marker enzymes at an early stage of melanoma progression, is typical. Acknowledgements: Supported by GACR 524/01/0162 and CAV S5045113 grants. [ABSTRACT FROM AUTHOR]