GROWTH-RATES OR RADIOBIOLOGICAL HYPOXIA ARE NOT CORRELATED WITH LOCALMETABOLITE CONTENT IN HUMAN-MELANOMA XENOGRAFTS WITH SIMILAR VASCULARNETWORK

Investigations were carried out on two lines of human melanomas (MF; n = 12 and EE; n = 13) xenografted in nude mice. The tumours were chara cterised by a similar vascular supply but showed a pronounced differen ce in the rate of volume growth and in the radiobiologically hypoxic f raction. The distribution of ATP, glucose and lactate in the tumours w as investigated using quantitative bioluminescence and single photon i maging. Concentrations of the metabolites were obtained as global valu es for the entire tumour mass, in regions with densely packed, structu rally intact tumour cells ('viable zones'), in areas with necrosis, st romal cells and fibrous material ('necrotic zones') and in adjacent no rmal tissue. In all melanomas investigated glucose concentrations were significantly lower and lactate concentrations were significantly hig her than in normal tissue. In contrast, no significant differences for ATP were detected. ATP and glucose concentrations were significantly less in necrotic than in viable tumour zones, whereas lactate concentr ations were nearly equal in these tumour parts. Corresponding results were obtained in central versus peripheral tumour zones. There was no dependency of global or regional metabolite concentrations on tumour s ize within the volume range 110-1470 mm(3). Based on this lack of depe ndency, metabolic concentrations were averaged over the whole tumour s ize range. Metabolite concentrations were not significantly different either globally or regionally between the two tumour entities investig ated, a finding which held true for all three metabolites registered. Thus, metabolite distributions apparently mirror the similarity in vas cularity of MF and EE melanomas rather than reflecting intrinsic prope rties with regard to tumour growth rates or susceptibility to radiatio n.