In vitro interaction of the photoactive anticancer porphyrin derivative photofrin II with low density lipoprotein, and its delivery to cultured human fibroblasts

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Abstract
Low density lipoprotein (LDL) doped with the anticancer mixture of hematoporphyrin derivatives Photofrin II (P2) competes with native LDL for binding to fibroblast receptors, despite a slight increase in the negative net charge related to the presence of acidic residues of porphyrins. P2 delivery to fibroblasts can be achieved by LDL, HDL3 or albumin doped with P2 (LDL‐P2, HDL‐P2 or A‐P2, respectively). P2 delivery to cells assessed by fluorescence measurement, is much more efficient, at low protein concentrations (10–20 ) by LDL‐P2 than by HDL‐P2 or A‐P2. Moreover, P2 delivery to cells by LDL‐P2 as a function of protein concentration is a saturable process, whereas P2 delivery by HDL‐P2 or A‐P2 is a linear process. Finally, reduction of the LDL‐receptor number by preincubation of fibroblasts in medium supplemented with lipoproteins results in a decrease of P2 delivery by LDL‐P2. These results suggest a special role of the LDL‐receptor pathway in P2 delivery to cells and could be of interest in cancer phototherapy by porphyrins.

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