Paul G. Munder

The influence of alkyl-lysophospholipids and lysophospholipid-activated macrophages on the development of metastasis of 3-Lewis lung carcinoma

Alkyl-lysophospholipids are synthetic analogs of natural occurring 2-lysophosphatidylcholine. They inhibit the development of metastasis of 3-Lewis lung tumor in the lung of C57Bl/6 mice if given i.v., i.c. or even orally as demonstrated by the increase of the median survival time and the number of surviving animals. Furthermore, i.v. injections of lysophospholipid-activated bone marrow macrophages increase the number of surviving animals and cause also a prolongation of the median survival time.

Cell propagation on films of polymeric fluorocarbon as a means to regulate pericellular pH and pO2 in cultured monolayers

In the intact animal, the pH, pCOZ and pOZ of the cell environment is under exquisite biochemical and physiological control. This state is not approximated by hitherto accessible techniques of monolayer cell culture; while bulk pH of the medium might be measured and even regulated electronically, this is rarely practised, and no means have been available to sense and control the pH, pCOZ and pOZ in the ceN layer. We are concerned that inadequate regulation of these parameters might introduce toxic effects and unwanted selective pressures into in vitro cell propagation, as well as clouding the biological significance of culture-dependent phenomena such as contact inhibition of movement, growth and biosynthesis [l-3] . The cellular effects of pCOZ (e.g. via formation of protein-carbamates) remain to be specified, but the need for precise regulation of pericellular pH is obvious. Moreover, it is established that oxygen tensions greater than that of air (hyperbaric) are acutely toxic to whole animal tissues [4] , as well as lymphocyte cultures [S] and can increase tumor incidence [6-l l] . The toxic effects are attributed to oxidation of protein-SH and polyenoic fatty acids in membrane phospholipids [ 121 . Only in pulmonary alveoli does the physiological oxygen level approach the pOZ of air, which most tissue culture systems attempt to approximate, while cells typically reside at much lower pOZ s, depending upon their vicinity to the proximal ends of systemic arterioles [ 131 . In most cells

Antineoplastic Actions of Ether Lipids Related to Platelet-Activating Factor

Many inorganic and organic biological response modifiers, which stimulate host defense mechanisms against infections and tumors (Oldham, 1982), share one biochemical effect. After phagocytosis by macrophages, they activate or induce a phospholipase A2 (E.C. 3.1.1.4) which degrades cellular phosphatidylcholine and phosphatidylethanolamine to the corresponding lyso compounds as 2-lysophospha-tidylcholine (2-LPC) and free fatty acids (Munder and Modolell, 1974; Munder et al., 1966, 1969, 1970, 1976). Compounds without immunopotentiating capacity do not alter the activity of phospholipase A2 (Munder et al., 1976).

Lysophosphatidylcholine (lysolecithin) and its synthetic analogues. Immunemodulating and other biologic effects

Since the early work of Bergenhem and Fahraeus on the hemolytic activity of naturally occurring 2-lysophosphatidylcholine (lysolecithin) (LPC) [12] this substance has off and on been considered as a biologically active compound. It is present as a minor phospholipid in the plasma (8–12%) [23] and cellular membranes (≥ 3%) [21, 27, for review 79]. It is highly surface-active (44.3 dyn/cm) [4] and, therefore, potentially cytotoxic if incubated with cells in serum — or plasma free —media [4, 30, 31, 33, 44, 72, 76]. Addition in sublytic amounts, however, stimulates phagocytosis [16, 20, 80], changes the surface properties of erythrocytes [36], increases the Concanavalin-A (Con-A)-induced agglutination of erythrocytes [75], and may be used as a cell-fusing agent [58]. Furthermore, it has been claimed to be involved in hypersensitivity [38, 70] and inflammatory reactions [17].

Antitumor activity of SRI 62-834, a cyclic ether analog of ET-18-OCH3

SRI 62-834, an analog of the antitumor agent ET-18-OCH3 in which the oxygen atom at carbon atom 2 has been incorporated into a five-membered heterocycle, has been prepared and evaluated as an antitumor agent. The compound exhibited good cytotoxicity in vitro against a variety of tumor cell lines and was as effective as ET-18-OCH3 given orally in the mouse Meth A sarcoma model. SRI 62-834 was shown to be an inhibitor of platelet-derived growth factor (PDGF), possibly at the receptor level, and platelet-activating factor (PAF) at the receptor level.

Increased membrane permeability for an antitumoral alkyl lysophospholipid in sensitive tumor cells

We have investigated cellular sensitivity to the antitumoral alkyl lysophospholipid (ALP) 1-O-octadecyl-2-O-methyl-rac-glycero-3-phosphocholine (ET-18-OCH3) in vitro. The permeation of this lipid into the cell was not influenced by metabolic inhibitors of ATP biosynthesis. ET-18-OCH3 uptake was not saturable within sublytic concentrations, but could be inhibited in part by cytochalasin B (CB) and dipyridamole. The activation energy of the CB-sensitive uptake process was increased up to threefold compared to CB-insensitive uptake. ET-18-OCH3 influx and equilibrium binding of ET-18-OCH3 were decreased in a fibrosarcoma cell variant (MethA) selected for ET-18-OCH3 resistance. The resistant MethA cells were also less sensitive to cytolysis by lysophosphatidylcholine and other ALP. After 72 hr, the resistant MethA cells had metabolized only 11.8% more of the absorbed ET-18-OCH3 than sensitive MethA cells. However, they tolerated at least a 30-fold concentration of this ALP. The uptake mechanism, which could be inhibited by CB, was less active in resistant MethA cells and several other ALP-resistant cell lines. The concentration of CB, required for maximal uptake inhibition, was increased more than four times in the ALP-sensitive tumor cell lines. CB-specific ET-18-OCH3 uptake was also enhanced after virus transformation of 3T3 fibroblasts by SV 40. Dipyridamole retarded the ET-18-OCH3-mediated cell destruction.

The interaction of liposomes with cells: The relation of cell specific toxicity to lipid composition

Abstract Liposomes, which have been proposed as agent carriers, can themselves produce a wide variety of effects on the viability of co-incubated cells. In this study we show that the lipid composition of empty liposomes produced varied effects on the viability, as measured by [3H]-thymidine incorporation, of leukemic cells and fibroblasts. Certain liposomal compositions, particularly those involving stearylamine, were highly toxic to both cell types. It is evident from this investigation that caution must be exercised in the choice of lipid composition if the effect of the liposomes is not to conceal that of the drug, or carried agent, either on the target cells in terms of therapeutic effect, or on normal cells in terms of toxicity. Normal lysophosphatides, having an acyl bond in sn-1, can be metabolised by both normal and leukemic cells; however the replacement of the acyl by an alkyl bond in a lysophosphatide requires an O-alkyl cleavage enzyme to be metabolised. Such an enzyme is present in a multifunctional oxygenase in normal cells but appears to be absent or inoperative in certain tumor cells. Coincubation of alkyl lysophosphatide containing liposomes is shown to produce selective destruction of L1210 leukemic cells; in addition the liposomal form of such analogs is suggested as being more effective against leukemic cells and less toxic to normal cells than when used in the free form.

Alkyl-lysophospholipid induced suppression of human lymphocyte response to mitogens and selective killing of lymphoblasts

Alkyl-analogs of 2-lysophosphatidylcholine have been found to inhibit the response of human peripheral blood lymphocytes to mitogens and allogeneic cells. Furthermore, these compounds kill selectively transformed lymphocytes in vitro while resting lymphocytes are not affected in their viability. The increased incorporation of fatty acids into cellular phospholipids during lymphocyte stimulation has been shown to be inhibited by these alkyl-lysophospholipids. Both resting and transformed lymphocytes could be shown to have an 1-0-alkyl-cleavage enzyme. Thus, selective cytotoxicity for lymphoblasts is not due to principal differences in the metabolism of alkyl-lysophospholipids as we have demonstrated to be the case between normal and leukemic cells, but is most likely due to the interference of these substances with the enhanced turnover of cellular phospholipids in stimulated lymphocytes.

Age-related changes in interleukin production in BALB/cNNia and SJL/J mice and their modification after administration of foreign macromolecules

In vitro production of Interleukin-2, -3, -4 and -10 by activated lymphocytes of BALB/cNNia and SJL/J was studied. While IL-2 production in BALB/c mice remains constant throughout the life span of the animals (8-113 weeks), an increase in production from stimulated SJL cells was seen. Age-related increases in IL-3 and IL-4 production occur between young and middle age (8-60 weeks) in both strains. Some organ differences in quantity of lymphokine produced were seen; the direction of age-related changes was the same for lymphocytes of spleen and MLN. The exceptional feature of BALB/cNNia was the relative stabilization of the levels of interleukin production, as animals approach old age. BALB/cNNia and SJL, which are at the two opposite extremes of lifespan, differ also in their response to molecular interventions: in BALB/cNNia fetal sheep liver extract and hemocyanin increase the output of interleukins. This is in striking contrast to the effects observed in older SJL mice in which the extract reduced the output of IL-3 and IL-4 by old animals, whereas hemocyanin increased the output of IL-2 and IL-3 at all ages tested.

Antitumor activity of ilmofosine (BM 41.440) in the3Lewis-lung carcinoma model

Ilmofosine (1-hexadecylthio-2-methoxymethyl-1,3-propanediol-phosphocholine, BM 41.440) is a thioether phospholipid with cytostatic/cytotoxic properties. The antineoplastic activity of this compound was investigatedin vivo in the3Lewis-lung carcinoma system.3Lewis lung tumor-bearing C57Bl/6 mice were treated with 0.625 to 40 mg Il-mofosine/kg per dayp.o. either from days 1 to 9 or from days 11 to 28 after intrafoot-pad tumor cell inoculation. Ilmofosine caused a significant dose-related response on tumor growth and metastases, expressed in terms of tumor diameter, tumor weight, survival time and number of metastases-free animals as compared to sham-treated and positive (cyclophosphamide) controls. The results suggest that direct cytostatic/cytotoxic effects, rather than immune-modulatory mechanisms, preferentially contribute to the antitumor activity of Ilmofosinein vivo.