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Biomedical subjects

P Hilgard

Publications and source records attributed to P Hilgard.

At least 19 recordsLinked to original sources
PubMed1992

Treatment of experimental DMBA induced mammary carcinoma with Cetrorelix (SB-75): a potent antagonist of luteinizing hormone-releasing hormone.

Cetrorelix, (Ac-D-Nal(2)1, D-Phe(4Cl)2, D-Pal(3)3, D-Cit6, D-Ala10)-LHRH (SB-75) is a new highly potent antagonist of LH-RH. In the model of DMBA-induced mammary carcinoma, this antagonist was very effective in reducing tumor mass. A rapid decrease in tumor weights to levels below 0.1 g total tumor mass was achieved with 300 micrograms/kg given sc. daily for 14 days. The weights of uteri and ovaries were reduced to about 40-50% of control values. In all treated rats the estrus cycle was interrupted and the animals remained in a state of anestrus. Microscopically, the effects of Cetrorelix on the tumors were characterized by a loss of mitotic activity, marked regression with apoptosis, an increase of stroma and differentiation towards a normal mammary architecture. On the basis of a dose-response curve, a dose of 100 micrograms/kg/d of Cetrorelix was determined as sufficient for a full antitumor response. Large DMBA-tumors with total tumor mass of about 6 g could also be treated very effectively with a dose of 100 micrograms/kg/d. To achieve a complete tumor regression, the treatment had to last 34 days. After the cessation of treatment with 100 micrograms/kg/d and regrowth of the tumors the animals were treated with the agonist Decapeptyl (Trp6-LHRH) using a dose of 50 micrograms/rat/d for 14 days. Again, the tumors responded well and regressed within 10 days. The treatment with an overlapping dose schedule of Cetrorelix and Decapeptyl showed a continuous antitumor response. A transient stimulation of tumor growth by the LH-RH agonist was not observed under these experimental conditions. In ovariectomized rats bearing DMBA-tumors, treatment with Cetrorelix and estradiol, produced no tumor growth inhibition as compared to estradiol control group, indicating that there is no estrogen nullifying effect of this antagonist on tumor cells in this model. On the basis of these results, Cetrorelix is a highly effective antitumor agent in this breast cancer model, which might also be useful under clinical conditions.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1991

Platelet aggregation inhibiting and anticoagulant effects of oligoamines, XVI: Cytostatic and cytotoxic side effects of oligoamines.

Selected synthetic oligoamines were able to inhibit (IC50) the growth of leukemic L 1210 cells in concentrations between 4-10 mumol/L. The essential structural features were at least two basic nitrogen functions in suitable distance, substituted with arylalkyl or alkyl groups. The favorable chain length is about eight carbon atoms. The cytostatic effect is complete after 30 min and cannot be washed out with buffer. Viability measurements showed that the leukemic cells were killed in a time dependent manner. As no influence on the cell nucleus could be observed this is most probably due to interaction with the cell membrane. When high local concentrations are applied in vivo, the oligoamines are toxic because of cytolytic properties. This toxicity can be overcome by administration of suitable prodrugs (LD50 greater than 1000 mg/kg).

Animals↗
PubMed1991

Investigation into the immunological effects of miltefosine, a new anticancer agent under development.

Miltefosine is the prototype of alkylphosphocholines, a new class of anticancer agents related to alkyl-lysophospholipids. These agents were considered to possess potent immunomodulatory properties. Miltefosine was highly active against the human KB tumour xenograft in nude mice, leading to growth inhibition as well as regression of large established tumours, which suggested that its mode of action was not mediated by the T cell system. In vivo natural killer cell activity was measured by chromium release of YAC-1 cells using spleen cells from treated animals as effector cells. Miltefosine had no significant effect on YAC-1 cytolysis. Similarly, the compound did not induce cytotoxic spleen cells against KB target cells. The results were identical when spleen cells from tumour-bearing animals were used. Humoral antibody production in rats following sheep red blood cell immunization was not changed by miltefosine pretreatment. Finally, the in vitro phagocytic activity of mouse bone marrow macrophages was not stimulated but rather inhibited in a dose-dependent manner. In conclusion, there is no experimental evidence that the miltefosine action is mediated by the host immune system and no major immunotoxicity was observed.

Animals↗
PubMed1990

Biotransformation of mafosfamide in P388 mice leukemia cells: intracellular 31P-NMR studies.

The intracellular transformation of cis-mafosfamide has been studied in P388 mice leukemia cells using 31P-NMR spectroscopy. For this purpose the cells were entrapped in low-gelling-temperature agarose threads. Internal pH of the cells, determined from the position of the intracellular inorganic phosphate, was 7.2. The cell membrane was permeable to 4-hydroxycyclophosphamide and aldophosphamide and less permeable to phosphoramide mustard. 4-Ketocyclophosphamide and carboxyphosphamide signals were not detectable in cells either sensitive or resistant to oxazaphosphorine treatment.

Animals↗
PubMed1990

Protection from ifosfamide-induced alopecia by topical thiols in young rats.

An animal model for testing substances that might prevent alopecia induced by oxazaphosphorines has been developed. It is based on the fact that the rat pups experience virtually total hair loss following administration of oxazaphosphorines. Using this model, we showed that epicutaneous treatment with sodium thioglycollate prevented ifosfamide-induced hair loss on the treated area. These experiments indicate that prevention of oxazaphosphorine-induced alopecia in man may be achieved by topical thiols.

Administration, Cutaneous↗
PubMed1990

D-19466, a new cyclobutane-platinum complex with antitumor activity.

D-19466, a new platinum complex, was characterized. It showed no nephrotoxic side-effects as determined by the measurement of blood urea. It was cytotoxic in vitro for tumor cells in concentrations comparable to or lower than cytotoxic concentrations of cisplatin. It had excellent anticancer activity in vivo against a number of murine experimental tumors, including a cisplatin-resistant P388 line. Clinical evaluation of this compound has therefore been initiated.

Animals↗
PubMed1990

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

Widespread local recurrence of breast cancer, untreatable by surgery or radiation therapy, can present a serious therapeutic problem predominantly in patients refractory to systemic therapy. In a phase I trial hexadecylphosphocholine, a new agent with high membrane affinity and antineoplastic activity was applied topically to affected skin areas of breast cancer patients. The results provide evidence that hexadecylphosphocholine may be an active agent in the topical treatment of skin metastases.

Administration, Topical↗
PubMed1990

Coagulant and fibrinolytic activities of a metastasising and non-metastasising tumour line.

The two types of transplantable methyl cholanthrene induced fibrosarcoma in rats was used to find out the possible relationship between the fibrinolytic, procoagulant activities and the metastasizing capacity of the tumours. The highly metastatic tumour seems to possess high fibrinolytic activity as compared to the low metastatic one. Interestingly enough, it was found that the procoagulant and fibrinolytic activities in the highly metastasising tumour bear inverse relationship with each other in relation to time of tumour growth. The procoagulant activity of the tumour bypasses factor VII and acts at factor X level. The plasminogen activator present in the tumour tissue has been characterized by sephadex G-200 column chromatography and PAGE.

Animals↗
PubMed1989

Augmentation of host antitumor immunity by low doses of cyclophosphamide and mafosfamide in two animal tumor models.

By cloning in vitro we have obtained two sublines of the L5222 rat leukemia, one with high (L5222-S) and the other with low (L5222-R) in vivo sensitivities to non-toxic doses of mafosfamide, a stabilized derivative of 4-hydroxy-cyclophosphamide. This sensitivity in vivo was not related to the cytotoxic activity of the drug in vitro. Treatment of rats bearing the L5222-S and of mice transplanted with the MOPC-315 plasmocytoma with low doses of mafosfamide or cyclophosphamide resulted in a high percentage of surviving animals, which were resistant to a subsequent tumor challenge. Viable leukemic cells were needed to establish antitumor immunity, since it was not possible to induce resistance by injection of mitomycin-C-treated, non-viable L5222 cells. The adoptive transfer of spleen cells from animals immune against the L5222-S and the MOPC-315 resulted in resistance of the syngeneic recipients against a rechallenge with tumor cells, provided that the animals were treated with an immunosuppressive dose (100 mg/kg) of cyclophosphamide prior to the spleen cell implantation. In nude mice treatment of the L5222 with low doses of mafosfamide also resulted in surviving animals, however resistance to a second tumor challenge occurred only sporadically. The data presented confirm that therapy with cyclophosphamide or mafosfamide enhances host antitumor immunity but, contrary to previous reports, it could be demonstrated that successful tumor rejection was independent of T cells.

Adjuvants, Immunologic↗
PubMed1989

Bone marrow purging with mafosfamide--a critical survey.

Autologous bone marrow transplantation (ABMT) is increasingly used to consolidate remissions, primarily in hematological disease. Various purging strategies have been developed to minimize the risk of reimplantation of tumor cells with the bone marrow autotransplant. Pharmacological purging with the oxazaphosphorine derivative mafosfamide has been studied extensively, and recent clinical data suggest that purging with mafosfamide may translate into superior remission duration if compared to nonpurged ABMT in acute leukemia. Chemical and experimental data relevant to mafosfamide-purging and clinical results are reviewed, with special emphasis on safety aspects.

Animals↗
PubMed1989

Evidence of a role for NK cells in oxazaphosphorine-mediated tumor regression.

The present studies showed that nude mice xenotransplanted with L5222 leukemia responded as did syngeneic BD IX rats to low doses of mafosfamide or cyclophosphamide. Unlike rats, nude mice rarely showed resistance to a second tumor challenge. The observation that concurrent treatment of rats with cyclosporin A did not alter the rate of survival clearly indicated a T-cell-independent mechanism of tumor defense. The incidence of lung colonies from i.v. injected Lewis lung-tumor cells could be enhanced by a high dose pretreatment with mafosfamide or cyclophosphamide, whereas pretreatment at low doses was inhibitory. Since identical experiments carried out in NK-cell-deficient C57Bl/6 "beige" mice did not show such an effect, NK cells appeared to represent a possible effector cell in oxazaphosphorine-mediated antitumor effects. This assumption was further supported by the fact that enhanced NK cell activity could be observed in the 51Cr release assay using spleen cells from mafosfamide-treated L5222-bearing rats. The transplantation of the unrelated syngeneic ovarian carcinoma OV-342 to animals that had previously been cured of L5222 leukemia did not lead to the rejection of this tumor. This indicates that a specific resistance against L5222 leukemia had developed. In contrast, a T-cell-dependent antitumor effect was demonstrated for mafosfamide in the MOPC-315 mouse plasmocytoma. Therefore, we conclude that the effector cell for tumor rejection depends on the type of tumor. This, of course, does not exclude a common target cell for the immunopharmacological activity of oxazaphosphorines.

Animals↗
PubMed1989

Hexadecylphosphocholine, a new ether lipid analogue. Studies on the antineoplastic activity in vitro and in vivo.

Hexadecylphosphocholine (He-PC) is a new compound synthesized according to the minimal structural requirements deducted from studies with other ether lipids. In vitro studies on He-PC revealed remarkable antineoplastic activity on HL60, U937, Raji and K562 leukemia cell lines. In addition, He-PC, applied orally, showed a superior effect in the treatment of dimethylbenzanthracene-induced rat mammary carcinomas when compared to intravenously administered cyclophosphamide. After oral application He-PC was well absorbed from the intestine and metabolized in the liver by phospholipases C and D. During a 5-week treatment no hematotoxic effects were detected. In a clinical pilot study on breast cancer patients with widespread skin involvement, topically applied He-PC showed skin tumor regressions without local or systemic side effects.

Animals↗
PubMed1989

Chloroacetaldehyde and its contribution to urotoxicity during treatment with cyclophosphamide or ifosfamide. An experimental study/short communication.

Based on clinical data, indicating that chloroacetaldehyde (CAA) is an important metabolite of oxazaphosphorine cytostatics, an experimental study was carried out in order to elucidate the role of CAA in the development of hemorrhagic cystitis. The data demonstrate that CAA after i.v. administration does not contribute to bladder damage. When instilled directly into the bladder, CAA exerts urotoxic effects, it is, however, susceptible to detoxification with mesna.

Acetaldehyde↗