Localisation and accumulation of a new carotenoporphyrin in two primary tumour models

We have investigated the tumour-localising properties and in vivo fluoresce nce kinetics of a hexamethoxylated carotenoporphyrin (CP6) in two primary t umour models: UV-B-induced early skin cancer in hairless mice and chemicall y induced mucosal dysplasia in the rat palate. CP6 fluorescence kinetics ar e investigated by measuring in vivo fluorescence spectra and images of the mouse skin and the rat palate at different time points after injection. For the tumour-localising properties, microscopic phase-contrast and fluoresce nce images are recorded. The in vivo fluorescence kinetics in the mouse ski n show localization of CP6 in the tumours. However, fluorescence microscopy images show that CP6 localises in the dermis and structures that are not r elated to the malignant transformation of the mouse skin. The fluorescence kinetics in the rat palate show a significant correlation between the degre e of malignancy and the CP6 fluorescence build-up time in the palate. The m icroscopic images show that CP6 fluorescence localises in the connective ti ssue and not in the dysplastic epithelium. In conclusion, CP6 does not loca lise preferentially in (pre-)cancerous tissue in the two primary tumour mod els studied hew, in contrast to reports about localisation of carotenoporph yrins in transplanted tumours. However, the CP6 build-up time in rat palate s correlates with the degree of malignancy and this might possibly be a use ful parameter in tumour detection. (C) 2000 Elsevier Science S.A. All right s reserved.