Induction of differentiation and tetraploidy by long-term treatment of C6 rat glioma cells with erucylphosphocholine.

Induction of differentiation represents a promising concept for chemotherapy of malignant gliomas, which are often refractory even to the combined treatment with surgery, irradiation and chemotherapy. Since anti-neoplastic alkylphosphocholines can induce differentiation of leukemic cell lines, the effects of the intravenously applicable alkylphosphocholine-derivative erucylphosphocholine (ErPC) on proliferation, morphology and differentiation of the rat glioma cell line C6 was examined in vitro. Short-term exposure to ErPC induced accumulation of the cells in the G2/M-phase of the cell cycle and apoptotic cell death. In contrast, continuous exposure of C6 rat glioma cells to sublethal ErPC doses (30 and 50 microM) caused both the formation of a slower growing tetraploid cell population and astrocytic differentiation. No resistance to in vivo obtainable ErPC concentrations was observed during this treatment. We conclude that ErPC-induced differentiation might be beneficial for a long-term adjuvant chemotherapy of low grade glioma.

Effects of miltefosine and other alkylphosphocholines on human intestinal parasite Entamoeba histolytica.

The protozoan parasite Entamoeba histolytica is the cause of amoebic dysentery and liver abscess. It is therefore responsible for significant morbidity and mortality in a number of countries. Infections with E. histolytica are treated with nitroimidazoles, primarily with metronidazole. At this time, there is a lack of useful alternative classes of substances for the treatment of invasive amoebiasis. Alkylphosphocholines (alkyl-PCs) such as hexadecyl-PC (miltefosine) were originally developed as antitumor agents, but recently they have been successfully used for the treatment of visceral leishmaniasis in humans. We examined hexadecyl-PC and several other alkyl-PCs with longer alkyl chains, with and without double bond(s), for their activity against two strains of E. histolytica. The compounds with the highest activity were oleyl-PC, octadecyl-PC, and nonadecenyl-PC, with 50% effective concentrations for 48 h of treatment between 15 and 21 microM for strain SFL-3 and between 73 and 98 microM for strain HM-1:IMSS. We also tested liposomal formulations of these alkyl-PCs and miltefosine. The alkyl-PC liposomes showed slightly lower activity, but are expected to be well tolerated. Liposomal formulations of oleyl-PC or closely related alkyl-PCs could be promising candidates for testing as broad-spectrum antiprotozoal and antitumor agents in humans.

Structure-activity relationships of four anti-cancer alkylphosphocholine derivatives in vitro and in vivo.

This study was carried out to investigate whether structure-activity relationships of alkylphosphocholines, a new group of anti-neoplastic agents, which had been detected in methylnitrosourea(MNU)-induced rat mammary carcinoma, can be transferred to in vitro systems. Therefore, the anti-neoplastic activity of 4 alkylphosphocholines (APCs) was compared in 6 tumor cell lines in vitro and in MNU-induced rat mammary carcinoma in vivo. The in vitro system consisted of 2 rat mammary-carcinoma-derived cell lines (1/C2 and 1/C32), as well as 2 human mammary-gland (MDA-MB-231 and MCF-7)- and gastrointestinal tract (HT-29 and KB)-derived tumor cell lines. As assessed by both cell counting and MTT-assay, the ranking of concentrations effecting 50% growth inhibition (IC50) was parallel in all cell lines for octadecylphosphocholine (18:0-PC), octadecenyl-(trans-9.10)-phosphocholine (t-18:1-PC) and octadecenyl-(cis-9.10)-phosphocholine (c-18:1-PC). Only hexadecylphosphocholine (16:0-PC) differed in its activity, being least active in 1/C2, 1/C32 and MDA-MB-231 cells, moderately active in KB and MCF-7 cells, and most active in HT-29 cells. The IC50 concentrations of APCs in the 2 rat mammary carcinoma cell lines significantly correlated with dosages effecting a 50% tumor growth delay in vivo. Remarkably, the 2 gastrointestinal cell lines were more sensitive to APC exposure than the mammary-carcinoma cell lines. In all cell lines except KB cells, growth-stimulation effects were seen in the concentration range preceding the anti-proliferative activity; in vivo, however, no accelerated cancer growth was observed. The in vitro system failed to describe the superior therapeutic ratio of c-18:1-PC, as assessed in vivo, because it does not take the relative sensitivity of tumor vs. normal cells into account. Complementary in vivo trials are therefore indispensable for a final evaluation. Comparison of the 2 in vitro assays shows good agreement of the interrelationship of IC50 values, those obtained by MTT assay being on average 25% higher than those obtained from cell counting.

Minimum safety requirements for preclinical testing.

A wide range of biological products for medicinal use can now be produced by novel biotechnology processes. These products include naturally occurring human proteins and peptides such as hormones, cytokines, blood products as well as monoclonal antibodies of murine and human origin and bacterial and viral antigens for use as vaccines. However, there are potential safety concerns that arise from the novel processes used in their manufacture and from the complex structural and biological characteristics of the products. The acute and repeated dose toxicity testing, pharmacodynamic and immunological testing and a range of product-specific biochemical and safety tests required for these products are described.

Characterization of the antitumor activity of hexadecylphosphocholine (D 18506).

Hexadecylphosphocholine (HPC) differs from ether lipids with known antitumor activity by its lack of the glycerol part. In the experiments described here HPC revealed outstanding antitumor activity in dimethylbenzanthracene (DMBA)-induced rat mammary tumors. A dose-response relationship was seen after daily oral treatment with complete suppression of tumor growth at doses of 46.4 mg/kg/day. There was no schedule dependence and the therapeutic efficacy was independent of the tumor weight at the initiation of therapy. Another autochthonous tumor, the benzo[a]pyrene-induced sarcoma of the rat did not respond to HPC treatment, indicating a highly selective spectrum of activity of the test compound. In comparison to an optimal single dose of cyclophosphamide, a single high dose of HPC was considerably more active against the DMBA tumor. At therapeutic dose levels no major toxicity of HPC was observed. Bone marrow suppression was not encountered, on the contrary, at high doses leukocytosis became apparent. The available pharmacological and toxicological data suggest that HPC may be useful in the treatment of human cancer.