Hexadecylphosphocholine in the topical treatment of skin metastases in breast cancer patients

Investigation of miltefosine-model membranes interactions at the molecular level for two different PS levels modeling cancer cells

Miltefosine (MLT) is a broad-spectrum drug included in the alkylphospholipids (APL) used against leishmania and various types of cancer. The most crucial feature of APLs is that they are thought to only kill cancerous cells without harming normal cells. However, the molecular mechanism of action of APLs is not completely understood. The increase in the phosphatidylserine (PS) ratio is a marker showing the stage of cancer and even metastasis. The goal of this research was to investigate the molecular effects of miltefosine at the molecular level in different PS ratios. The effects of MLT on membrane phase transition, membrane orders, and dynamics were studied using DPPC/DPPS (3:1) and DPPC/DPPS (1:1) multilayer (MLV) vesicles mimicking DPPS ratio variation, Differential Scanning Calorimetry (DSC), and Fourier Transform Infrared spectroscopy (FTIR). Our findings indicate that miltefosine is evidence at the molecular level that it is directed towards the tumor cell and that the drug's effect increases with the increase of anionic lipids in the membrane depending on the stage of cancer.

Evaluation of release and pharmacokinetics of hexadecylphosphocholine (miltefosine) in phosphatidyldiglycerol-based thermosensitive liposomes

Hexadecylphosphocholine (HePC, Miltefosine) is a drug from the class of alkylphosphocholines with an antineoplastic and antiprotozoal activity. We previously reported that HePC uptake from thermosensitive liposomes (TSL) containing 1,2-dipalmitoyl-sn-glycero-3-phosphodiglycerol (DPPG₂) into cancer cells is accelerated at mild hyperthermia (HT) resulting in increased cytotoxicity. In this study, we compared HePC release of different TSL formulations in serum. HePC showed rapid but incomplete release below the transition temperature (T_m) of investigated TSL formulations in serum. Short heating (5 min) to 42 °C increased HePC release from DPPG₂-TSL (T_m = 41 °C) by a factor of two in comparison to body temperature (37 °C). Bovine serum albumin (BSA) induced HePC release from DPPG₂-TSL comparable to serum. Furthermore, multilamellar vesicles (MLV) were capable to extract HePC from DPPG₂-TSL in a concentration- and temperature-dependent manner. Repetitive exposure of DPPG₂-TSL to MLV at 37 °C led to a fast initial release of HePC which slowed down after subsequent extraction cycles finally reaching approx. 50% HePC release. A pharmacokinetic study in rats revealed a biphasic pattern with an immediate clearance of approx. 50% HePC whereas the remaining 50% HePC showed a prolonged circulation time. We speculate that HePC located in the external leaflet of DPPG₂-TSL is rapidly released upon contact with suitable biological acceptors. As demonstrated by MLV transfer experiments, asymmetric incorporation of HePC into the internal leaflet of DPPG₂-TSL might improve HePC retention in presence of complex biological media and still give rise to HT-induced HePC release.

Lipids and Membrane Microdomains: The Glycerolipid and Alkylphosphocholine Class of Cancer Chemotherapeutic Drugs

Synthetic antitumor lipids are metabolically stable lysophosphatidylcholine derivatives, encompassing a class of non-mutagenic drugs that selectively target cancerous cells. In this chapter we review the literature as relates to the clinical efficacy of these antitumor lipid drugs and how our understanding of their mode of action has evolved alongside key advances in our knowledge of membrane structure, organization, and function. First, the history of the development of this class of drugs is described, providing a summary of clinical outcomes of key members including edelfosine, miltefosine, perifosine, erufosine, and erucylphosphocholine. A detailed description of the biophysical properties of these drugs and specific drug-lipid interactions which may contribute to the selectivity of the antitumor lipids for cancer cells follows. An updated model on the mode of action of these lipid drugs as membrane disorganizing agents is presented. Membrane domain organization as opposed to targeting specific proteins on membranes is discussed. By altering membranes, these antitumor lipids inhibit many survival pathways while activating pro-apoptotic signals leading to cell demise.

Conditional Knockdown of Osteopontin Inhibits Breast Cancer Skeletal Metastasis

High osteopontin (OPN) expression is linked to breast cancer bone metastasis. In this study we modulated osteopontin levels conditionally and investigated any related antineoplastic effects. Therefore, we established cell clones from human breast cancer MDA-MB-231 cells, in which the expression of OPN is regulated by the Tet-Off tet-off system. These cells, which conditionally express a specific miRNA targeting OPN, were used for in vitro studies as well as for a bone metastasis model in nude rats. Changes in whole-genome expression elicited by conditional OPN knockdown and vesicle formation were also analyzed. The alkylphosphocholine erufosine was used for combination therapy. Conditional OPN knockdown caused mild anti-proliferative, but more intensive anti-migratory and anti clonogenic effects, as well as partial and complete remissions of soft tissue and osteolytic lesions. These effects were associated with specific gene and protein expression modulations following miRNA-mediated OPN knockdown. Furthermore, high levels of OPN were detected in vesicles derived from rats harboring breast cancer skeletal metastases. Finally, the combination of OPN inhibition and erufosine treatment caused an additive reduction of OPN levels in the investigated breast cancer cells. Thus, knockdown of OPN alone or in combination with erufosine is a promising strategy in breast cancer skeletal metastasis treatment.

Dimethylsphingosine and miltefosine induce apoptosis in lung adenocarcinoma A549 cells in a synergistic manner

Lung cancer is one of the most common and lethal types of oncological diseases. Despite the advanced therapeutic approaches, the prognosis for lung cancer still remains poor. Apparently, there is an imperative need for more efficient therapeutic strategies. In this work we report that concurrent treatment of human adenocarcinoma A549 cells with specific concentrations of two antitumor agents, the sphingosine kinase 1 inhibitor N, N dimethylsphingosine (DMS) and the alkylphosphocholine miltefosine, induced synergistic cytotoxic effect, which was confirmed by calculation of the combination index. The simultaneous action of these agents, induced significant decrease of A549 cell number, as well as pronounced morphological alterations. Combined drugs caused substantial apoptotic events, and significant reduction of the pro-survival marker sphingosine- 1-phosphate (S1P), when compared to the individual treatments with each of the anticancer drugs alone. Miltefosine is known to affect the synthesis of choline-containing phospholipids, including sphingomyelin, but we report for the first time that it also reduces S1P. Here we suggest a putative mechanism underlying the effect of miltefosine on sphingosine kinase 1, involving miltefosine-induced inhibition of protein kinase C. In conclusion, our findings provide a possibility for treatment of lung cancer cells with lower concentrations of the two antitumor drugs, DMS and miltefosine, which is favorable, regarding their potential cytotoxicity to normal cells.

In vivo studies of the effectiveness of novel N-halomethylated and non-halomethylated quaternary ammonium salts in the topical treatment of cutaneous leishmaniasis

The physicochemical properties of four N-halomethylated and one non-halomethylated ammonium salts, with proven in vitro antileishmanial activity, were determined according to pharmaceutical standard procedures. The effectiveness and toxicity of these compounds were assessed in hamsters infected with Leishmania (Viannia) braziliensis and compared to that showed by meglumine antimoniate. Animals were followed during 90 days after the completion of treatment. Therapeutic response was determined according to the reduction of size of skin lesions. Toxicity was determined by the effect of compounds on body weight changes and serum levels of renal and hepatic metabolites. The effectiveness of compound 4 was similar to that showed by intralesional administration of meglumine antimoniate and better than that of the other ammonium salts. Levels of creatinine, alanine amino transferase, and blood urea nitrogen in serum were not significantly different between treatment groups, including healthy or untreated hamsters. Results imply that compound 4 has potential as a pharmaceutical active ingredient in the development of new and better formulations for the treatment of cutaneous leishmaniasis.

Synthesis of Novel Quaternary Ammonium Salts and Their in Vitro Antileishmanial Activity and U-937 Cell Cytotoxicity

This work describes the synthesis of a series of quaternary ammonium salts and the assessment of their in vitro antileishmanial activity and cytotoxicity. A preliminary discussion on a structure-activity relationship of the compounds is also included. Three series of quaternary ammonium salts were prepared: (i) halomethylated quaternary ammonium salts (series I); (ii) non-halogenated quaternary ammonium salts (series II) and (iii) halomethylated choline analogs (series III). Assessments of their in vitro cytotoxicity in human promonocytic cells U-937 and antileishmanial activity in axenic amastigotes of L. (Viannia) panamensis (M/HOM/87/UA140-pIR-eGFP) were carried out using the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide) micromethod. Antileishmanial activity was also tested in intracellular amastigotes of L. (V) panamensis using flow cytometry. High toxicity for human U937 cells was found with most of the compounds, which exhibited Lethal Concentration 50 (LC₅₀) values in the range of 9 to 46 μg/mL. Most of the compounds evidenced antileishmanial activity. In axenic amastigotes, the antileishmanial activity varied from 14 to 57 μg/mL, while in intracellular amastigotes their activity varied from 17 to 50 μg/mL. N-Chloromethyl-N,N-dimethyl-N-(4,4-diphenylbut-3-en-1-yl)ammonium iodide (1a), N-iodomethyl-N,N-dimethyl-N-(4,4-diphenylbut-3-en-1-yl)ammonium iodide (2a), N,N,N-trimethyl-N-(4,4-diphenylbut-3-en-1-yl)ammonium iodide (3a) and N,N,N-trimethyl-N-(5,5-diphenylpent-4-en-1-yl)ammonium iodide (3b) turned out to be the most active compounds against intracellular amastigotes of L. (V) panamensis, with EC₅₀ values varying between 24.7 for compound 3b and 38.4 μg/mL for compound 1a. Thus, these compounds represents new “hits” in the development of leishmanicidal drugs.

Caenorhabditis elegans as a platform to study the mechanism of action of synthetic antitumor lipids

Drugs capable of specifically recognizing and killing cancer cells while sparing healthy cells are of great interest in anti-cancer therapy. An example of such a drug is edelfosine, the prototype molecule of a family of synthetic lipids collectively known as antitumor lipids (ATLs). A better understanding of the selectivity and the mechanism of action of these compounds would lead to better anticancer treatments. Using Caenorhabditis elegans, we modeled key features of the ATL selectivity against cancer cells. Edelfosine induced a selective and direct killing action on C. elegans embryos, which was dependent on cholesterol, without affecting adult worms and larvae. Distinct ATLs ranked differently in their embryonic lethal effect with edelfosine > perifosine > erucylphosphocholine >> miltefosine. Following a biased screening of 57 C. elegans mutants we found that inactivation of components of the insulin/IGF-1 signaling pathway led to resistance against the ATL edelfosine in both C. elegans and human tumor cells. This paper shows that C. elegans can be used as a rapid platform to facilitate ATL research and to further understand the mechanism of action of edelfosine and other synthetic ATLs.

Antileishmanial drug discovery: comprehensive review of the last 10 years

This review covers the current aspects of leishmaniasis including marketed drugs, new antileishmanial agents, and possible drug targets of antileishmanial agents.

Anticancer mechanisms and clinical application of alkylphospholipids

Synthetic alkylphospholipids (ALPs), such as edelfosine, miltefosine, perifosine, erucylphosphocholine and erufosine, represent a relatively new class of structurally related antitumor agents that act on cell membranes rather than on DNA. They selectively target proliferating (tumor) cells, inducing growth arrest and apoptosis, and are potent sensitizers of conventional chemo- and radiotherapy. ALPs easily insert in the outer leaflet of the plasma membrane and cross the membrane via an ATP-dependent CDC50a-containing 'flippase' complex (in carcinoma cells), or are internalized by lipid raft-dependent endocytosis (in lymphoma/leukemic cells). ALPs resist catabolic degradation, therefore accumulate in the cell and interfere with lipid-dependent survival signaling pathways, notably PI3K-Akt and Raf-Erk1/2, and de novo phospholipid biosynthesis. At the same time, stress pathways (e.g. stress-activated protein kinase/JNK) are activated to promote apoptosis. In many preclinical and clinical studies, perifosine was the most effective ALP, mainly because it inhibits Akt activity potently and consistently, also in vivo. This property is successfully exploited clinically in highly malignant tumors, such as multiple myeloma and neuroblastoma, in which a tyrosine kinase receptor/Akt pathway is amplified. In such cases, perifosine therapy is most effective in combination with conventional anticancer regimens or with rapamycin-type mTOR inhibitors, and may overcome resistance to these agents. This article is part of a Special Issue entitled Phospholipids and Phospholipid Metabolism.

Lysolipid containing liposomes for transendothelial drug delivery

BACKGROUND

Designing efficient 'vectors', to deliver therapeutics across endothelial barriers, in a controlled manner, remains one of the key goals of drug development. Recently, transcytosis of liposome encapsulated fluorescence marker calcein across a tight cell barrier was studied. The most efficient liposomes were found to be liposomes containing sufficient amount of alkyl phospholipid (APL) perifosine. APLs have similar structure as lysophosphatidyl choline (LPC), since APLs were synthesized as metabolically stable analogues of LPC, which increases endothelial permeability directly by inducing endothelial cell contraction, resulting in formation of gaps between endothelial cells. Since one of the unique properties of lysolipid, containing liposomal formulations is dynamic equilibrium of lysolipids, which are distributed among liposomes, micelles, and free form, such liposomes represent a reservoir of free lysolipids. On the other hand lysolipid containing liposomes also represent a reservoir of an encapsulated hydrophilic drug.

PRESENTATION OF THE HYPOTHESIS

We hypothesize that free lysolipids, with highest concentration in vicinity of drug carrying liposomes, compromise endothelial integrity, primarily where concentrations of liposomes is the highest, in a similar manner as LPC, by formation of gaps between endothelial cells. Liposome encapsulated drug, which leaks from liposomes, due to liposome destabilization, caused by lysolipid depletion, can therefore be efficiently transported across the locally compromised endothelial barrier.

TESTING THE HYPOTHESIS

This hypothesis could be verified: by measuring binding of perifosine and other lysolipids to albumin and to lysophospholipid receptor (LPL-R) group; formation of stress fibers and subsequent cell contraction; activation of RhoA, and endothelial barrier dysfunction; by a synthesis of other LPC analogues with high critical micellar concentration and measuring their effect on transendothelial permeability in presence and absence of albumin.

IMPLICATIONS OF THE HYPOTHESIS

We propose that lysolipid containing liposomal formulations might be used as nonspecific transendothelial transport vector, since leakage of liposome encapsulated active drug occurs simultaneously with the release of the lysolipids. The concentration of the active drug is therefore expected to be the highest at the site of compromised endothelial barrier. By appropriate choice of the lysolipids an endothelial barrier would stay open only for a short time. Use of such liposomes would potentially maximize the delivery of the drug while limiting the passage of toxic substances and pathogens across the endothelial barrier. Combining lysolipid containing liposomes with superparamagnetic iron oxide nanoparticles or a targeting ligand might be required to efficiently localize drug delivery to a disease affected tissue and to avoid endothelial disruption over the entire body.

Glycosidated phospholipids: uncoupling of signalling pathways at the plasma membrane

Cell expansion and metastasis are considered hallmarks of tumour progression. Therefore, efforts have been made to develop novel anti-cancer drugs that inhibit both the proliferation and the motility of tumour cells. Synthetic alkylphospholipids, compounds with aliphatic side chains that are ether linked to a glycerol backbone, are structurally derived from platelet-activating factor and represent a new class of drugs with anti-proliferative properties in tumour cells. These compounds do not interfere with the DNA or mitotic spindle apparatus of the cell. Instead, they are incorporated into cell membranes, where they accumulate and interfere with lipid metabolism and lipid-dependent signalling pathways. Recently, it has been shown that the most commonly studied alkylphospholipids inhibit proliferation by inducing apoptosis in malignant cells while leaving normal cells unaffected. This review focuses on a novel group of synthetic alkylphospholipids, the glycosidated phospholipids, which contain carbohydrates or carbohydrate-related molecules at the sn-2 position of the glycerol backbone. Members of this subfamily also exhibit anti-proliferative capacity and modulate the cell adhesion, differentiation, and migration of tumour cells. Among this group, Ino-C2-PAF shows the highest efficacy and low cytotoxicity. Apart from its anti-proliferative effect, Ino-C2-PAF strongly reduces cell motility via its inhibitory effect on the phosphorylation of the cytosolic tyrosine kinases FAK and Src. Signalling pathways under the control of the FAK/Src complex are normally required for both migration and proliferation and play a prominent role in tumour progression. We intend to highlight the potential of glycosidated phospholipids, especially Ino-C2-PAF, as a promising new group of drugs for the treatment of hyperproliferative and migration-based skin diseases.

Rationale and clinical application of alkylphospholipid analogues in combination with radiotherapy

Concurrent treatment with radiotherapy and chemotherapy has emerged as an effective strategy to improve clinical outcome of cancer. In addition to combining radiation with classical anticancer agents, several new biological response modifiers are under investigation in pre-clinical and clinical studies. Synthetic alkylphospholipids are anticancer agents that in contrast to most anticancer drugs, do not target DNA, but insert in the plasma membrane and subsequently induce a broad range of biological effects, ultimately leading to cell death. Alkylphospholipids kill tumor cells directly by induction of both apoptotic and non-apoptotic cell death, and indirectly by interference with critical signal transduction pathways involved in phospholipid metabolism and survival. Due to their distinct mode of action, these drugs are considered as attractive candidates to combine with radiotherapy. In this review, we will discuss several alkylphospholipids that reached clinical application. These include first-generation alkyl-lysophospholipids edelfosine and ilmofosine, second-generation alkylphosphocholine-prototype miltefosine and more recently developed analogues perifosine and erucylphosphocholine. We focus on mechanisms of action and the rationale to combine these agents with radiotherapy. The preclinical results on molecular targeting underlying this approach will be reviewed, concluded with first clinical data on combined treatment of radiotherapy with perifosine.

Miltefosine induces apoptosis-like death in Leishmania donovani promastigotes

Miltefosine (hexadecylphosphocholine [HePC]) has proved to be a potent oral treatment for human visceral leishmaniasis due to Leishmania donovani. The molecular mechanisms that contribute to the antileishmanial activity of HePC are still unknown. We report that in wild-type promastigotes of Leishmania donovani HePC is able to induce a cell death process with numerous cytoplasmic, nuclear, and membrane features of metazoan apoptosis, including cell shrinkage, DNA fragmentation into oligonucleosome-sized fragments, and phosphatidylserine exposure. None of these changes were detected in an HePC-resistant clone treated with the same drug concentration. Therefore, HePC does not appear to kill L. donovani promastigotes by a direct toxic mechanism but, rather, kills the promastigotes by an indirect one. Pretreatment of wild-type promastigotes with two broad caspase inhibitors, z-Val-Ala-DL-Asp(methoxy)-fluoromethylketone and Boc-Asp(methoxy)-fluoromethylketone, as well as a broad protease inhibitor, calpain inhibitor I, prior to drug exposure interfered with DNA fragmentation but did not prevent cell shrinkage or phosphatidylserine externalization. These data suggest that at least part of the apoptotic machinery operating in wild-type promastigotes involves proteases. Identification of the death-signaling pathways activated in HePC-sensitive parasites appears to be essential for a better understanding of the molecular mechanisms of action and resistance in these parasites.

Effects of etherlipid analogs on cell membrane functions

Hexadecylphosphocholine and other etherlipid-derived substances show a pronounced antiproliferative activity on neoplastic cells and a broad spectrum of other biological effects on many cell types in vitro and in vivo. Though the precise molecular mechanism by which these etherlipid analogs act still remains unresolved, it seems clear that it most probably involves some essential function of the cell membrane. We investigated the effect of different etherlipids with and without cytotoxic activity in etherlipid-susceptible and -resistant tumor cell lines on three important membrane functions. We observed various inhibitory activities on endocytosis and the uptake of small precursor molecules as sugars, amino acids, and alcohols by toxic and nontoxic substances in resistant as well as susceptible cells. There was no correlation between the antiproliferative characteristics of the compounds and the effects on these membrane transport functions. Furthermore, the substances reduced the number of membrane tumor necrosis factor-alpha receptors regardless of their antiproliferative properties. The results of these investigations suggest that etherlipid analogs may interfere with many membrane functions in an unspecific manner. Therefore, many of the previously reported biological effects of etherlipids have to be viewed under a different light. Future investigation on these compounds should always contain appropriate control substances and cell models to really prove the specificity of the observed effects.

Hexadecylphosphocholine does not influence phospholipase D and sphingomyelinase activity in human leukemia cells

Hexadecylphosphocholine (HePC) is the first representative of the alkylphosphocholines (APC), a new group of biologically active compounds. HePC has pronounced antiproliferative effects on neoplastic cells in vitro and in vivo. The molecular mechanism by which HePC exerts its biological effects is still under investigation. Recently there has been growing evidence that HePC probably interferes with cellular signalling via phospholipases. It has been shown to inhibit both forms of phospholipase C (PLC), the phosphatidylinositol- and the phosphatidylcholine-specific PLC, and phospholipase A2. Here we present data showing that HePC inhibits the activity of phospholipase D in vitro, whereas the action of this enzyme in leukemic cell lines is not affected. Furthermore HePC does not seem to disturbed the activity of sphingomyelinase, another enzyme of phospholipid metabolism which has been shown to play an important role in cellular signalling as well.

Effects of hexadecylphosphocholine on phosphatidylcholine and phosphatidylserine metabolism in human lymphoma cells

Hexadecylphosphocholine (HePC) belongs to a new group of antineoplastic agents, the alkylphosphocholines (APC). HePC shows a broad spectrum of biological effects in various cells in vitro and in vivo. It has pronounced antiproliferative effects on neoplastic cells. The molecular mechanism by which HePC exerts its biological effects is still under investigation. By generating a HePC-resistant cell variant of the lymphoma cell line Raji, we established a model to investigate which molecular mechanism may be responsible for the antiproliferative action of HePC. Here we present data showing that HePC substantially interferes with the metabolism of cellular phosphatidylcholine (PC) and phosphatidylserine (PS) in the human lymphoma cell line Raji. HePC leads to an inhibition of PC synthesis via CDP-choline and as a compensatory mechanism enhances the generation of PC via PS indicating that the reduced PC synthesis seems to significantly disturb cellular homeostasis. In HePC-resistant Raji cells, PC synthesis via CDP-choline is constitutively less active and is not further reduced by HePC. Resistant Raji cells do not seem to use the alternative pathway of PC synthesis via PS nor can this be induced by HePC. The resistance mechanism may therefore be independent of cell membrane metabolism.

Randomized, double-blind, placebo-controlled, multicenter trial of 6% miltefosine solution, a topical chemotherapy in cutaneous metastases from breast cancer

PURPOSE

To compare 6% miltefosine solution (Miltex; Asta Medica, Frankfurt, Germany), a new topical cytostatic drug, with placebo as palliative treatment for cutaneous metastases from breast cancer.

PATIENTS AND METHODS

In a double-blind, placebo-controlled, multicenter phase III study, a total of 52 patients with inoperable progressive skin lesions from histologically or cytologically confirmed breast cancer, not manageable by radiotherapy or systemic treatment, with superficial or flat skin lesions (estimated depth of invasion < or = 1 cm) were randomized to receive either 6% miltefosine solution or placebo. The solution was applied at the dose of 2 drops/10 cm(2), once daily during the first week and twice daily thereafter until treatment failure.

RESULTS

Treatment groups were well balanced for patient characteristics at study entry except for a small difference in age. Time to treatment failure (TTF), the primary parameter of this study, showed miltefosine solution to be significantly superior to placebo (P = .007); the median TTF in the miltefosine solution group was nearly three times longer than that in the placebo group (56 days v 21 days). The rate of response based on intention to treat patients was 33.3% for miltefosine solution compared with 3.7% for placebo (P = .006). Cutaneous reactions were seen mainly in the miltefosine group, with the type and frequency similar to those observed in previous studies.

CONCLUSION

6% Miltefosine solution is confirmed as an effective palliative treatment option for cutaneous metastases from breast cancer. Skin reactions, when present, are well tolerated and only occasionally require cessation of treatment.

Effects of hexadecylphosphocholine on thrombocytopoiesis

Hexadecylphosphocholine (HePC) is the first representative of the alkylphosphocholines, a novel group derived from the cytotoxic etherlysophospholipids. HePC shows a broad spectrum of antiproliferative effects in neoplastic cells in vitro and in vivo. HePC has been tested successfully in several clinical studies. One of the remarkable features of this compound has been the induction of a leucocytosis and a thrombocytosis in most of the patients receiving HePC systemically. In this paper, we have investigated the biological and molecular mechanisms by which HePC exerts this interesting effect. We found that HePC acts as an unspecific costimulator on human megakaryocytic proliferation in a soft agar assay system predominantly together with thrombopoietin (TPO). Furthermore, HePC leads to the synthesis and secretion of several haematopoietic growth factors in monocytes and bone marrow fibroblasts, determined by the direct measurement of growth factors in cellular supernatants and by the measurement of growth factor mRNA in cell extracts. Thus, HePC seems to produce the increase of blood platelets in tumour patients by two different mechanisms.

Phase II study of miltefosine 6% solution as topical treatment of skin metastases in breast cancer patients

Topical treatment of skin metastases with a cytotoxic agent is attractive for its easy self-administration and absence of major systemic interference. Miltefosine exerts its cytotoxicity by acting on cell membrane phospholipids and can be administered topically. Twenty breast cancer patients with progression of skin metastases were treated with a 6% solution of miltefosine, which was topically administered once daily during the first week and twice daily thereafter. Sixteen out of 20 patients also had metastatic disease at other sites. Concomitant systemic treatment when ongoing for at least 2 months prior to study entry was permitted, and consisted of chemotherapy and hormonal therapy in seven and nine patients, respectively. Prior palliative cytotoxic and hormonal therapy had been administered to 11 and 19 patients, respectively. No grade 3 and 4 toxicity occurred. Miltefosine therapy was discontinued in two patients due to nausea and in one patient due to skin toxicity. Grade 1 and 2 adverse skin reactions, and nausea and vomiting were seen in 11 and two patients, respectively. In 18 patients evaluable for response, four partial responses were noted (response rate 22%), while seven patients had stable disease. Three partial responses were observed in patients in whom the skin lesions were smaller than 1.5 cm2. Median duration of response was 2.5 months and median time to progression for all patients was 1.9 months. In this study topically applied miltefosine for metastatic skin lesions of breast cancer showed modest activity in a relatively heavily pretreated patient population, without serious systemic toxicity.

Separation and quantification of alkylphosphocholines by reversed phase high performance liquid chromatography

Alkylphosphocholines represent a new class of drugs with remarkable antineoplastic and antiprotozoal activity. For instance, hexadecylphosphocholine has been approved for the topical treatment of skin metastasis. In addition, it was successfully studied in India for the treatment of leishmaniasis. Different phase-I and phase-II-trials resulted in cure rates of more than 97%. To optimize antitumor or antiprotozoal activity, we have prepared alkylphosphocholines differing in chain length and unsaturation. For the qualitative and quantitative analysis of these longer chain analogues, we have used isocratic high performance liquid chromatography. The separation of the alkylphosphocholines with different chain lengths in this reversed phase HPLC system was achieved on a YMC-TMS column with a mobile phase consisting of methanol-water (85:15; v/v) at a flow rate of 1.0 ml/min. Furthermore the cis-/trans-isomers such as oleylphosphocholine and elaidylphosphocholine were clearly separated on a YMC-C8 column with a methanol-water mixture (80:20; v/v) as mobile phase. In the described reversed phase HPLC systems simple refractive index detection and UV detection allow the sensitive and quantitative determination of alkylphosphocholines. These methods are very important for reproducible identification and quantitative determination of saturated and mono-unsaturated alkylphosphocholines with alkyl residues containing up to 25 carbon atoms.

Human urinary bladder carcinoma cell lines respond to treatment with alkylphosphocholines

Alkylphosphocholines (APC) constitute a new group of antineoplastic agents without haematological toxicity. Their first clinically available derivative hexadecylphosphocholine (miltefosine) is locally used to control skin metastases of breast cancer. Since intravesical chemotherapy represents a form of topical treatment we investigated whether a new APC with a long alkyl chain would be active against 5637 and EJ bladder cancer cell lines. Their antineoplastic activity was inversely related to the alkyl chain length of the respective APC. Erucylphosphocholine and its congener with modified phosphocholine head erucylphospho-N,N,N-trimethylpropanolamine were the most effective derivatives. APC with alkyl chains over 16 carbons in length induced programmed cell death in both cell lines, as determined by oligonucleosomal DNA fragmentation and morphology. The distinct antineoplastic effects lead us to predict that urinary bladder instillation of APC will be of therapeutic benefit for patients with urinary bladder neoplasia.

Clinical pharmacology of anticancer agents in relation to formulations and administration routes

In the past years, alternative administration routes and pharmaceutical formulations of anticancer agents have been investigated in order to improve conventional chemotherapy treatment. The impact of these adjustments on the pharmacokinetics and pharmacodynamics is discussed. A review of the literature shows many examples of alternative administration forms of anticancer agents with improved pharmacokinetics. Local administration routes have been investigated in order to reduce the systemic toxicity and to enhance the local efficacy of conventional chemotherapy. Oral administration of anticancer agents is preferred by patients for its convenience and its potential for outpatient treatment. In addition, oral administration facilitates a prolonged exposure to the cytotoxic agent. However, poor bioavailability and substantial interpatient variability are noted as limitations for oral chemotherapy. Increased tumour selectivity can also be achieved by the use of specific pharmaceutical formulations, such as liposomes and macromolecular drug conjugates. The composition of these formulations often determine the pharmacokinetic behaviour of the formulated drug. In conclusion, several alternative administration forms of anticancer agents have been designed in the past years, with the potential for improvement of conventional chemotherapy, however, more extensive clinical evaluation of these novel strategies is warranted to prove their real clinical value.

Phase II trial of topically applied miltefosine solution in patients with skin-metastasized breast cancer

Skin deposits from breast cancer can present serious therapeutic problems, especially when resistant to conventional therapy. Topical application of a cytotoxic drug may represent an attractive new treatment modality devoid of major systemic toxicity. Miltefosine was selected because of its efficacy in breast cancer models. A mixture of alkylated glycerols of various chain lengths and water was used as the pharmaceutical vehicle to dissolve and to further facilitate tissue penetration of miltefosine. In our Institute a phase II study was performed to determine the efficacy and tolerability of topically applied miltefosine in patients with cutaneous metastases from breast cancer. Thirty-three patients in total entered the trial. A 6% miltefosine solution was applied once daily in the first week and twice daily in the following weeks. The planned minimum treatment duration was 8 weeks. We found an overall response rate of 43% for 30 evaluable patients, composed of 23% complete response and 20% partial response. The median response duration was 18 weeks, range 8-68. Toxicity consisted mainly of localized skin reactions, which could be controlled by a paraffin-based skin cream and, where appropriate, by dose modification. No systemic toxicities were observed. We conclude that topical miltefosine is an effective treatment modality in patients with skin metastases from breast cancer.

Cytotoxic etherphospholipid analogues

1. Alkyllyso-derivatives of physiologic cell membrane phospholipids show remarkable cytostatic and cytotoxic activity on many malignant tumor cell lines and tumors in vitro and in vivo. Three of these etherphospholipid analogues have already been tested in clinical phase II studies and one of these compounds, hexadecylphosphocholine (HePC), is now commercially available as a drug for the treatment of mammary carcinoma in Germany. 2. Etherphospholipid analogues possess a variety of interesting biological characteristics like induction of cellular maturation, inhibition of tumor cell invasion or modulation of the immune response with high potential value for tumor therapy. 3. Though there have been extensive investigations on the biochemical mode of action of these substances, the precise mechanism responsible for the majority of biological effects has not yet been identified. 4. In recent years growing evidence has been accumulated that etherphospholipid analogues substantially interfere with intracellular signal transduction.

[Spectrographic studies on the radioresistance of Miltex and miltefosine]

AIM

With simultaneous application of Miltex and radiation therapy in the combined treatment of topical relapses and skin metastases in breast carcinoma patients the question arises, how radioresistant is the new cytotoxic agent. Because of the long penetration times of the active agent miltefosine the answer is important with particular regard to the time of the external application of Miltex.

MATERIAL AND METHOD

After the application of a single dose of 10 Gy we studied the stability of the commercial preparation and its active agent miltefosine by means of absorption spectroscopy.

RESULTS

Immediately following the irradiation no alterations in absorption spectra of Miltex and miltefosine were found. However, 2 and 8 h post radiation the absorption curves of Miltex and miltefosine solutions were distinctly changed. The radiation induced changes of Miltex dilutions were smaller than those of the miltefosine solutions. For the commercial preparation the amount of the radiation-induced destruction is 0.10.

CONCLUSIONS

Consequently Miltex has shown a sufficient radioresistance or its decrease in the effectiveness is small. With daily single doses of 2 Gy in the radiotherapy of the topical relapses and skin metastases the destruction degree should be reduced to 0.02 assuming linear changes. Because of the distinct changes in the spectra and relative slow penetration of miltefosine in various cell lines [10, 11, 14] we will propose an application of the commercial cytotoxic agent 5 h before the radiation fractions. The smaller effect on Miltex is discussed in relation to the solution mediators of the active agent.

Determination of alkylphosphocholines by high-performance liquid chromatography with light-scattering mass detection

A rapid and sensitive method for the determination of five different alkylphosphocholines including the antineoplastic phospholipid analogues hexadecylphosphocholine and octadecylphosphocholine is presented. The method is based on the separation of the lipids by high-performance liquid chromatography and quantitation by light-scattering mass detection. The lower limit of detection is approximately 50 pmol for each alkyphosphocholine tested. Quantitation is linear over the range 0.05-75 nmol. Hexane-isopropanol extracts of cultured cells can be applied to the column without further cleanup. The high resolution of separation and the sensitivity of detection render this method useful for pharmacokinetic investigations dealing with the uptake of alkylphosphocholines into different types of cells.

Topical administration of hexadecylphosphocholine in patients with cutaneous lymphomas: results of a phase I/II study

BACKGROUND

Hexadecylphosphocholine is a new antineoplastic drug that inhibits tumor cell growth directly and, in addition, might have immunoregulatory properties.

OBJECTIVES

We investigated the topical application of this phospholipid in patients with cutaneous lymphoma.

METHODS

Twenty-four patients with histologically documented cutaneous lymphoma were treated for 8 weeks. Lesions that responded to treatment were biopsied and evaluated histologically.

RESULTS

Of 15 patients with cutaneous T-cell lymphomas, 12 were evaluable. Two complete remissions, four partial remissions, and one minor remission were observed. Of seven patients with B-cell lymphomas, six were evaluable. One complete remission, three partial remissions, one case of stable disease, and one case of progressive disease were seen. However, histologic monitoring demonstrated only a partial clearing of infiltrating lymphocytes in lesions that showed a partial or complete response clinically. Both patients with lymphomatoid papulosis had complete clearing of the lesions clinically. An objective response rate (partial and complete response) of 56% (10/18) was achieved in the patients with cutaneous lymphoma who were treated in this study.

CONCLUSION

Hexadecylphosphocholine appears to be effective topically in the treatment of some cases of cutaneous lymphomas.

Hexadecylphosphocholine differs from conventional cytostatic agents

Alkylphosphocholines, and especially their main representative hexadecylphosphocholine (HPC), show high anticancer activity in methylnitrosourea (MNU)-induced autochthonous rat mammary carcinoma. The regression of MNU-induced rat mammary carcinoma during HPC treatment can be evaluated by computed tomography and sonography. This allows a noninvasive monitoring of therapy in vivo (tumor size, morphology, and blood supply). Both diagnostic modalities can show a rapid concentric decrease in tumor volume as well as the appearance of cystic, scarry, and necrotic areas in the tumor tissue as a result of HPC treatment. In addition, prior to, during and after therapy tumor perfusion can be assessed by color Doppler sonography in vivo. A more than 4-fold difference in HPC efficacy was observed when the colony growth of explanted MNU-induced mammary carcinoma cells was measured in the methylcellulose colony assay (IC50 = 180 mumol HPC/l) and the Hamburger Salmon colony assay (IC50 = 740 mumol HPC/l). In the latter assay, growth of concomitantly seeded untransformed cells, especially of fibroblasts, is much lower than in the methyl-cellulose colony assay. We therefore assume that the antitumor efficacy of HPC against MNU-induced mammary carcinoma is enhanced by neighboring cells such as fibroblasts. Cell culture experiments with the three MNU-induced rat mammary carcinoma cell clones 1-C-2, 1-C-30, and 1-C-32 revealed IC50 values in the range of 50-70 mumol HPC/l. The volume of 1-C-2 cells increased up to 4-fold after 72 h of permanent exposure to 100 mumol HPC/l, a concentration that completely inhibited proliferation of tumor cell numbers without being cytotoxic. Nucleotide triphosphate levels dropped significantly after 24 h and were slowly restored in spite of continued exposure. After 72 h, they nearly reached those levels observed in plateau-phase cells. This suggests that HPC-induced growth inhibition has similarities with physiologically occurring growth arrest. Finally, replication of RNA viruses and DNA viruses was suppressed 30-fold and 7-fold, respectively, at low concentrations of HPC (12 mumol/l), which caused no or negligible growth inhibition in the virus-harboring cells, thus demonstrating specific antiviral activity of HPC. From these observations we conclude that HPC differs in many important aspects from conventional cytostatic agents and is certainly worth following-up in further investigations.

Antitumour activity of miltefosine alone and after combination with platinum complexes on MXT mouse mammary carcinoma models

Miltefosine, an alkylphosphocholine structurally related to alkyllysophospholipids showed highly selective antitumour activity against the hormone-sensitive variant of the s.c. transplantable MXT mouse mammary adenocarcinoma, the ovary-dependent MXT (M3.2), whereas it was inactive against the hormone-insensitive MXT (M3.2) OVEX variant. A dose of 32 mg/kg miltefosine p.o. daily for 5 weeks was well tolerated. Histopathological evaluation gave no signs of gastroenteral toxicity. After therapy the microarchitecture of the MXT (M3.2) tumours changed from that of a moderately differentiated adenocarcinoma to that of an anaplastic mammary carcinoma. A dose of 16 mg/kg miltefosine p.o. daily, though in effective per se, enhanced the antitumour activity of suboptimal i.p. doses of cisplatin and the hormone-like platinum analogue meso-1,2-bis(2,6-dichloro-4-hydroxyphenyl) ethylenediamine]dichloroplatinum(II). Furthermore, it was shown, that miltefosine exhibited no (anti)hormonal properties. However, the mechanism of action of miltefosine remains unclear.

Inhibition of phospholipase C delta by hexadecylphosphorylcholine and lysophospholipids with antitumor activity

The antineoplastic compound hexadecylphosphorylcholine (HPC) was shown to be a highly effective inhibitor of phospholipase C delta (PLC delta 1), with an I50 of about 30 nmol/mL (30 microM) in the presence and absence of 200 microM spermine. A number of lysophospholipids, of which HPC can be considered to be a structural analog, also inhibited PLC. Lysosphingomyelin, lysophosphatidylserine, and lysophosphatidylcholine exhibited I50 values of 15, 10, and 7 nmol/mL, respectively, in the presence of 200 microM spermine. The I50 values were increased to 21-53 nmol/mL in the absence of spermine. N,N-Dimethylsphingosine and N,N,N-trimethylsphingosine, which inhibit the metastatic potential of human and murine tumor cells, were weak activators of PLC delta 1. It is postulated that HPC is more effective as an antineoplastic agent than lysophospholipids because HPC is metabolized slowly, while the lysophospholipids are metabolized rapidly in vivo.

Cytotoxic effects of anticancer agents on subconfluent and multilayered postconfluent cultures

The cytotoxic effects of conventional (doxorubicin, 5-fluorouracil, cisplatin) and investigational (2',2'-difluorodeoxycytidine, hexadecylphosphocholine, EO9, rhizoxin) anticancer drugs were studied in subconfluent and multilayered postconfluent cultures of human colon and ovarian carcinoma cell lines. Chemosensitivity was assessed 4 days after a 24-h drug exposure with the sulphorhodamine B assay. Except for rhizoxin, all drugs tested yielded an EC50 (drug concentration producing absorbance readings 50% lower than those of non-treated wells) in postconfluent cultures that were higher than an EC50 obtained with subconfluent cultures. Compared with subconfluent cultures, postconfluent cultures showed decreased cellular nucleotide concentrations and ATP/ADP ratios, in addition to an increased percentage of G0/G1 cells. The activity of DT-diaphorase, a reductase involved in the bioactivation of EO9, was similar in sub- and postconfluent cultures. These results indicate similarity of the postconfluent model presented with those obtained with in vivo models and more complex in vitro techniques.

Characterization of two human mammary carcinomas, MT-1 and MT-3, suitable for in vivo testing of ether lipids and their derivatives

The human mammary carcinomas MT-1 and MT-3 originate from surgical material and were transplanted in nude mice. Both tumors have been classified as estradiol- and progesterone receptor-negative. Therapeutic doses of hormones and anti-hormones remained without growth inhibitory effect. MT-1 and MT-3 proved to be sensitive to conventional cytostatic drugs used for treatment of mammary carcinomas; striking is their sensitivity to ether lipids. Therefore, they are considered suitable tumor models for this class of substances.