Accumulation of protoporphyrin-IX (PpIX) in leukemic cell lines following induction by 5-aminolevulinic acid (ALA)

We investigated the amounts of protoporphyrin IX (PpIX) accumulated in noni nduced cells and following 5-aminolevulinic acid (ALA)-induction. Following ALA administration PpIX increased in all leukemic cell lines under investi gation (HEL 26-fold, HL60 6-fold, Jurkat 3-fold, ML2 2-fold) but not in lym phocytes. Compared to other cell lines studied, HEL cells showed the lowest basal level of PpIX and the largest relative increase in PpIX. Despite a h igh increase following ALA treatment, the PpIX level in HEL cells is almost as low as in lymphocytes. It is in agreement with their relatively low sen sitivities of ALA-induced photodynamic therapy (ALA-PDT) shown previously [ (Grebenova, D., Cajthamlova, H., Bartosova, J., Marinov, J., Klamova, H., F uchs, O., Hrkal, Z., 1998. Selective destruction of leukemic cells bg photo -activation of 5-aminolevulinic acid induced protoporphyrin IX. J. Photoche m. Photobiol. B: Biol. 47, 74-81)]. The ferrochelatase activities in the in dividual cell lines are in good inverse correlation with PpIX amounts accum ulated in the ALA-induced cells, but not with the relative increase (ratio) of PpIX levels from basal to ALA-induced ones. This is most apparent in HE L cells and lymphocytes. There is probably different regulation of heme bio synthesis in erythroid cells, which are therefore not suitable fur the stud ies of ALA-PDT mechanism. PpIX as accumulated more extensively in absence o f fetal calf serum than in its presence. The amounts of PpIX accumulated in cells decreased exponentially with increasing fetal calf serum concentrati on. (C) 2000 Elsevier Science Inc. All rights reserved.