Role of high-, low- and very low-density lipoproteins in the transport and tumor-delivery of hematoporphyrin in vivo

150

Summary Plasma lipoproteins, such as low-density lipoprotein (LDL), have been proposed to enhance the delivery of hydrophobic photosensitisers to malignant tissue since tumour cells have been shown to have increased numbers of LDL receptors. We have investigated the role of this receptor in the cellular accumulation of the photosensitiser benzoporphyrin derivative (BPD). We observed that: (1) [`4C]BPD-LDL accumulation by LDL receptor-negative fibroblast cell lines was insignificant compared with normal cell lines; (2) there was no evidence that BPD dissociated from LDL during incubation with the cells; and (3) chemical acetylation of LDL markedly decreased the uptake of ['4C]BPD-LDL. We conclude, therefore, that virtually all of the photosensitiser accumulated by the cells was due to specific binding and internalisation via the LDL receptor. Subsequent in vivo studies in M-1 (methylcholanthrene-induced rhabdomyosarcoma) tumour-bearing DBA/2J mice showed that tumour accumulation of BPD associated with native LDL was significantly (P<0.01) enhanced over that of acetyl-LDL-associated BPD. These results indicate that the LDL receptor is responsible for the accumulation of LDL-associated BPD both in vitro and in vivo. Thus, utilisation of this delivery system may provide for improvements in photodynamic therapy in clinical practice.

mentioning

confidence: 99%

Evidence for low-density lipoprotein receptor-mediated uptake of benzoporphyrin derivative

Allison

Ph²,

Levy³

1994

150

“…Alternatively, or in addition, decreased drug uptake in some cells of spheroids may be related to membrane changes that might occur with increasing spheroid size. Serum lipoproteins have a high affinity for haematoporphyrins and drug uptake may be via receptor-mediated endocytosis of complexes of porphyrin with low density lipoprotein (LDL; see Barel et al (1986) for discussion). There may be a decrease in the number of LDL receptors in some cells when grown in close contact, leading to an increase in the heterogeneity of drug intake.…”

Section: Discussionmentioning

confidence: 99%

Size-dependent resistance of human tumour spheroids to photodynamic treatment

West

1989

Summary Spheroids derived from the human colon adenocarcinoma cell line, WiDr, were exposed to lOpgmlPl Photofrin II and irradiated with light (700nm, 5OmWcm-2). Compared with exponentially growing monolayer cultures, cells in spheroids of 100, 250 and 500um diameter were respectively 1.8, 2.5 and 22-fold less sensitive. The small resistance of plateau-phase cultures (1.3-fold) was insuflicient to account for this marked spheroid size-dependent resistance. For monolayer cultures and for spheroids of 100 and 250pm diameter, the results were the same whether irradiations were carried out pre-or post-trypsinisation. However, there was a difference for the largest spheroid size: when irradiations were carried out pre-trypsinisation, spheroids were more resistant than when irradiations were given post-trypsinisation. Drug extraction studies showed that there was no difference in the average drug uptake between cultures of exponentially growing or plateau-phase cells, and lOOpm diameter spheroids while 250 and 500pm diameter spheroids took up proportionally 0.5 and 0.4 as much drug. Cell contact effects, drug heterogeneity between cells, hypoxia and problems in drug penetration are suggested as possible reasons for the resistance of large spheroids to photodynamic treatment.During the past decade there has been increasing interest in the potential of photodynamic therapy (PDT) as a new modality for the treatment of cancer. Although many of the factors determining response have been investigated, there are still many areas of the biology of PDT yet to be studied. The use of multicellular spheroids as a tool for the investigation of tumour response to other therapies is well established. They are useful, for example, for assessing the contribution of hypoxia (Sutherland et al., 1970;West et al., 1984; West & Sutherland, 1987), diffusion limitations (Sutherland et al., 1979;Durand, 1981), cell contact effects (Durand & Sutherland, 1972;West & Stratford, 1987), and repair processes (Durand & Sutherland, 1972;West et al., 1984) in the response of cells to a particular treatment.The resistance of spheroids to photodynamic treatment has been documented previously (Christensen et al., 1984). However, to date, there has been no systematic study of the effect of spheroid size on the development of this resistance. In addition, there have been conflicting reports of the effect of cell growth phase on sensitivity to photodynamic treatment. Christensen et al. (1984) reported that log-and plateau-phase NHIK 3025 cells were equally sensitive to haematoporphyrin derivative (HPD) plus light, while BenHur et al. (1987) showed that V79 cells in the plateau-phase of growth were more sensitive than exponentially growing cells to photosensitisation with chloroaluminium phthalocyanine.The following work describes a study of the effect of spheroid size on photosensitisation by Photofrin II. In addition, the role of the growth phase of cells during drug exposure has been investigated. The end-point used was clonogenic cell survival. Spheroid...

“…Similar pharmacokinetic data are obtained for normal mice injected with 0.5 mg kg-': as shown in Table III the photosensitiser is slowly eliminated from the liver while there are similar concentrations of iso-BOSiNc in the spleen at times between 1 and 4 weeks after injection. molecular weight class of proteins, the peak 'B' represents the lipoproteins and the peak 'C' represents mainly albumin and globulins (Barel et al, 1986). Clearly, the dye is distributed among all serum proteins, although the fraction associated with peak 'A' is substantially reduced upon injection of 0.5 mg kg-'.…”

Section: Pharmacokinetic Studiesmentioning

confidence: 98%

“…The content of proteins, triglycerides, phospholipids and cholesterol was measured in order to calculate the total lipoprotein mass (holoprotein) (Barel et al, 1986).…”

Section: Chemicalsmentioning

confidence: 99%

Liposome-delivered Si(IV)-naphthalocyanine as a photodynamic sensitiser for experimental tumours: pharmacokinetic and phototherapeutic studies

Cuomo

Jori²,

Rihter³

et al. 1990

SummaryThe pharmacokinetic behaviour and phototherapeutic effectiveness of bis(di-isobutyloctadecylsiloxy)-2,3-naphthalocyanatosilicon (iso-BOSiNc) incorporated into dipalmitoyl-phosphatidylcholine (DPPC) liposomes have been studied in Balb/c mice bearing an MS-2 fibrosarcoma. We found that iso-BOSiNc i.v. -injected at a dose of 0.5 mg kg-' b.w. is preferentially transported by serum lipoproteins; in particular, the photosensitiser is associated with LDL (57.8% of total recovery in the serum) and HDL (35.7%) while minor amounts are associated to VLDL (2.63%) and other serum proteins (3.89%), Iso-BOSiNc concentrations greater than 1 gig g-' of tissue are recovered from the tumour at 12 -48 h after administration while the ratio of iso-BOSiNc concentration in tumour and peritumoral tissue is greater than 10. Upon increasing the injected dose, the additional iso-BOSiNc is almost exclusively bound by HDL, which leads to large uptake of the photosensitiser by liver and spleen. The efficiency of iso-BOSiNc as a photodynamic agent was measured upon irradiation with a different dose-rate for a total light dose of 450 J cm-2. The extent of tumour necrotic area increases as a function of the time after the end of PDT treatment and reaches a maximum level after about 24 h. Moreover, the necrotic area is linearly dependent on the irradiation dose-rate up to 100 mW cm-2. In all there is substantial evidence that iso-BOSiNc delivered in a liposomal dispersion is a highly effective photosensitizer for PDT of tumours.Photodynamic therapy (PDT) is a method of cancer treatment, based on photosensitisation of the tumour to selected wavelengths of visible light by phototherapeutic agents (Wilson & Jeeves, 1987). At present PDT is applied at the clinical level using haematoporphyrin-IX (Hp-IX) and haematoporphyrin derivative (HpD) (Dougherty, 1987) as photodynamic agents. However, Hp and HpD show a small efficiency of red light absorption; moreover, HpD is a highly heterogeneous mixture of porphyrins, while the clinically used Hp contains about 15% porphyrin-type impurities (Jori et al., 1983).Other classes of photosensitisers, such as phthalocyanines and chlorins, are provided with better red light-absorbing properties than Hp: their absorption maxima are located around 670 nm with extinction coefficients about 105 M-l cm-'; moreover, they are usually characterised by a good degree of purity (Zhou, 1989). Recently, naphthalocyanines have been proposed as PDT agents (Firey & Rodgers, 1987), since these compounds show intense absorption (a> IO M-l cm-') around 780 nm, namely in a spectral interval where light penetration through the skin is approximately twice that at 630 nm (Wilson & Jeeves, 1987).In this work we have studied the pharmacokinetic and phototherapeutic properties of bis(di-isobutyloctadecylsiloxy) -2,3-naphthalocyanato silicon (iso-BOSiNc) in mice bearing a transplanted tumour. Flash photolysis studies (Firey & Rodgers, 1987;Ford et al., 1988) have shown that isoBOSiNc triplet state has a long natural lifetime (331 ji...