Destruction of erythroleukaemic cells by photoactivation of endogenous porphyrins

Abstract

Cancer therapy ideally should be based on high selectivity of the therapeutic agent for the transformed cells, low specificity for normal tissues and high cytotoxic efficiency to the target tumour. These requirements are partially fulfilled by haematoporphyrin derivative (HPD) phototherapy.The method is based on the capability of porphyrins to be selectively localized in malignant tumours. Light activation of the localized porphyrin induces damage to mitochondria, cellular organelles, membranes, DNA, and specific proteins by singlet oxygen, produced under aerobic conditions and possibly by hydroxyl radicals (Reviewed by Moan, 1986;& Van Steveninck et al., 1986). Photodynamic therapy is based on administration of an HPD solution to the cancer patient and later on, illumination of the tumour by a 630nm laser light beam. The treated area undergoes necrosis, with minimal changes in the surrounding tissues (Dougherty, 1984; Land, 1984;Berenbaum et al., 1982).Although HPD is quite an effective tumour localizer, the trend is to synthesize new porphyrin-compounds with higher tumour localizing capacities, and being chemically well defined, to overcome the main problem of HPD viz. its complex porphyrin composition and aggregation state (Kessel & Chou, 1985;Evensen et al., 1984). Recently, a variety of new molecules with good tumour localization and sensitization properties were introduced into experimental systems, like haematoporphyrin di-ethers (Rimington et al., 1987) and chlorin-porphyrin ester . Uroporphyrin I was reevaluated mainly for diagnostic applications (El-Far & Pimstone, 1986). On the other hand, it is well known that the natural protoporphyrin is an excellent photosensitizer, inducing haemolysis and light sensitivity of the skin in porphyric patients (Meyer & Schmid, 1978). It is a poor tumour localizer despite its high photo-activity potential on in vitro incubated cells (Malik & Djaldetti, 1980). In addition, protoporphyrin is biosynthesized in low amounts, by all tumour cells, as well as non-transformed tissues, while in specific transformed cells such as erythroleukaemia, it can be produced more efficiently (Marks & Rifkind, 1978). In their proerythroblastic phase the enzymatic activity of porphyrin biosynthesis was found to be constitutive, except for the first enzyme, the ALA-synthase which is the rate limiting step of the pathway and is inducible (Sassa, 1976), and iron uptake from transferrin (Lasky et al., 1986). Therefore, in order to induce porphyrin synthesis by erythroblasts, exogenous 5-ALA must be supplied to circumvent the first limiting enzyme .Mice injected with 5-ALA showed porphyrin production in the skin, an effect similar to that of 5-ALA in cultured Friend erythroleukaemic cells (Pottier et al., 1986). From both these systems it can be concluded that the cellular concentration of porphyrin can be increased by exogenous addition of the precursor for porphyrins.The purpose of the present study was to determine whether endogenous porphyrins produced from 5-ALA erythroleukaemic cells ca...

A mechanistic study of cellular photodestruction with 5-aminolaevulinic acid-induced porphyrin

“…Other approaches for achieving better localisation include local administration of the photosensitiser (Amano et al, 1988;Bachor et al, 1992). Recently, there has been considerable interest in a different approach to PDT in which a precursor, ALA, is administered and synthesis of the photosensitiser, PpIX, accomplished in situ (Pottier et al, 1986;Malik & Lugaci, 1987;Malik et al, 1989;Divaris et al, 1990;Kennedy et al, 1990;Bedwell et al, 1992;Kennedy & Pottier, 1992;Loh et al, 1992Loh et al, , 1993aRebeiz et al, 1992). The synthesis of ALA is the rate-limiting step in non-erythroid cells in the pathway of haem biosynthesis (Martin, 1985) (Rebeiz et al, 1992).…”

A regulatory role for porphobilinogen deaminase (PBGD) in δ-aminolaevulinic acid (δ-ALA)-induced photosensitization?

“…Tissue concentrations were computed from the fluorescence values obtained by a titration of a protoporphyrin IX (PPIX) standard (Porphyrin Products, Logan, UT, USA). Protoporphyrin IX was used as the standard as previous reports demonstrated that PPIX is the major contributor to the fluorescence detected after exposure of cells to 8-ALA (Malik and Lugaci, 1987;Kennedy and Pottier, 1992;Hua et al, 1995). Values obtained in the present study were almost identical to those we reported previously when porphyrin fluorescence was measured on tissue extracts (Hua et al, 1995).…”

In vivo fluorescence kinetics and photodynamic therapy using 5-aminolaevulinic acid-induced porphyrin: increased damage after multiple irradiations

“…The increased selective effects on TT treated at 60 min p.i. could also be the result of translocation within the cell of porphyrin from the mitochondrion to less sensitive sites (Kessel, 1986;Malik & Lugaci, 1987). Since PpIX is formed in the mitochondrion and because the mitochondrion is very sensitive for PDT damage (Hilf, 1986;Salet, 1986) an increased effect may be expected when treating at an interval where the rate of fluorescence increase is maximal as done in group C.…”