Photodynamic therapy of tumours: value of quantum chemical procedures for characterization of new drugs. Prediction of the electronic structure of zinc(II) phthalocyanine with special emphasis on triplet state excitation energies

Zinc(II) phthalocyanine is the active component of the liposomal formulation CGP 55847 which showed a high activity in photodynamic therapy in a variety of animal tumours. The photophysical properties of zinc(II) phthalocyanine have been studied in detail and compared to those of Photofrin, the only sensitizing agent approved so far for phase III/IV clinical trials. Since the efficacy of photodynamic therapy intrinsically depends on the spectroscopic features of the sensitizer, quantum chemical methods have proven to be an efficient means for optimizing chemical structures. As will be shown, a simple modification of the time-honoured INDO model of Pople allows a prediction of the singlet and triplet state properties of molecules of the size of zinc(II) phthalocyanine with an rms error of ≤ 1000 cm⁻¹.     

Nafenopin, a hypolipidemic and non-genotoxic hepatocarcinogen increases intracellular calcium and transiently decreases intracellular pH in hepatocytes without generation of inositol phosphates

Addition of nafenopin (30-300 microM to 45Ca2+ preloaded cultured hepatocytes caused a rapid and concentration-dependent increase in 45Ca2+ efflux in a manner similar to vasopressin, as evidenced by the loss of radioactivity from the cells. In contrast to vasopressin, addition of nafenopin to [3H]inositol prelabelled hepatocytes in culture did not increase [3H]inositol phosphate production. When added simultaneously with vasopressin, nafenopin inhibited the vasopressin-stimulated [3H]inositol phosphate production. In hepatocyte suspensions isolated from rats treated for 1 week with a carcinogenic dose of nafenopin (1000 ppm in their daily food) the incorporation of [3H]inositol into the phosphoinositide fraction, particularly phosphatidylinositol 4-phosphate and phosphatidylinositol 4,5-bisphosphate, was much less than that in hepatocytes isolated from untreated rats. The vasopressin-stimulated [3H]inositol phosphate production was also decreased. Experiments with hepatocyte suspensions preloaded with Ca2+ or pH sensitive fluorescent indicators demonstrated that addition of nafenopin caused an increase in intracellular free Ca2+ and transient acidification of the cells. The increase in [Ca2+]i was decreased by only about 25% when extracellular calcium was removed indicating that nafenopin mainly mobilizes Ca2+ from intracellular stores. The recovery to basal pH was amiloride-sensitive indicating the importance of Na+/H+ exchange in pH recovery after intracellular acidification. Amiloride also inhibited DNA synthesis induced by nafenopin and by epidermal growth factor in cultured hepatocytes; but this effect occurred concomitantly with inhibition of basal DNA synthesis. We suggest that hepatic Ca2+ mobilization induced by nafenopin may play an important role in the mechanism by which nafenopin exerts its physiological as well as its tumour promotive activity upon chronic treatment with carcinogenic doses.     

Retrohepatic vena cava reconstruction with polytetrafluoroethylene graft

The case of an 18-month-old male who underwent a right hepatic lobectomy for hepatoblastoma with extensive involvement of the retrohepatic vena cava is presented. The retrohepatic vena cava was replaced with an expanded polytetrafluoroethylene graft. This graft was proved patent by ultrasonography 2 years after operation. The child has no evidence of recurrent hepatoblastoma. The results of grafting the retrohepatic vena cava have been notoriously poor. It is widely believed that a prosthetic vena cava graft cannot be expected to remain patent. Our experience with polytetrafluoroethylene and previous reports using Dacron and polytetrafluoroethylene have shown that long-term patency of retrohepatic vena cava replacement with synthetic graft can be successful.