Esophageal varices during pregnancy in the course of cirrhosis

Esophageal variceal bleeding is one of the most severe complications that may occur during pregnancy in patients with liver cirrhosis. It may result in death of the mother and the fetus. Therefore, screening endoscopy should be performed both before the conception and in the second trimester. Endoscopic band ligation is a method of choice in case of variceal bleeding. Close cooperation of hepatologist, obstetrician-gynecologist and endoscopist is recommended in order to provide maximum care and increase the chances of successful delivery. We present a case of 28-years-old primigravida, at 27 weeks pregnant with esophageal varices and liver cirrhosis.

Mayer-Rokitansky-Küster-Hauser syndrome - case studies, methods of treatment and the future prospects of human uterus transplantation

OBJECTIVE

We aimed to present patients with the Mayer-Rokitansky-Küster-Hauser syndrome (MRKH) coming from one center and presenting all the possibilities of its treatment, at the forefront with the uterine transplantation.

PATIENTS AND METHODS

The presented work is an example of different types of MRKH syndrome diagnosed in 25 women who were diagnosed in the Department of Gynecological Endocrinology due to the primary amenorrhea from 01/2001 to 06/2018.

RESULTS

Patients suffering from MRKH syndrome are capable of having genetic offspring but are unable to give birth to their own child, due to an absence of the uterus, blindly terminated vagina, and normal ovaries. Patients suffering from this syndrome have the opportunity to receive treatment in accordance with their current needs. However, there are many medical, technical, and ethical limitations in achieving the most important therapeutic target: uterine transplantation and childbirth.

CONCLUSIONS

Until a few years ago, patients with an absolute uterine factor of infertility, including women with MRKH syndrome, had a real choice of only two equally controversial options giving a chance for motherhood - surrogacy and adoption. However, modern transplantation has shown that a third option - a uterine transplant - exists and is available.

Preclinical study on combined chemo- and nonviral gene therapy for sensitization of melanoma using a human TNF-alpha expressing MIDGE DNA vector

Nonviral gene therapy represents a realistic option for clinical application in cancer treatment. This preclinical study demonstrates the advantage of using the small-size MIDGE(®) DNA vector for improved transgene expression and therapeutic application. This is caused by significant increase in transcription efficiency, but not by increased intracellular vector copy numbers or gene transfer efficiency. We used the MIDGE-hTNF-alpha vector for high-level expression of hTNF-alpha in vitro and in vivo for a combined gene therapy and vindesine treatment in human melanoma models. The MIDGE vector mediated high-level hTNF-alpha expression leads to sensitization of melanoma cells towards vindesine. The increased efficacy of this combination is mediated by remarkable acceleration and increase of initiator caspase 8 and 9 and effector caspase 3 and 7 activation. In the therapeutic approach, the nonviral intratumoral in vivo jet-injection gene transfer of MIDGE-hTNF-alpha in combination with vindesine causes melanoma growth inhibition in association with increased apoptosis in A375 cell line or patient derived human melanoma xenotransplant (PDX) models. This study represents a proof-of-concept for an anticipated phase I clinical gene therapy trial, in which the MIDGE-hTNF-alpha vector will be used for efficient combined chemo- and nonviral gene therapy of malignant melanoma.

Ready-to-use injectable calcium phosphate bone cement paste as drug carrier

Current developments in calcium phosphate cement (CPC) technology concern the use of ready-to-use injectable cement pastes by dispersing the cement powder in a water-miscible solvent, such that, after injection into the physiological environment, setting of cements occurs by diffusion of water into the cement paste. It has also been demonstrated recently that the combination of a water-immiscible carrier liquid combined with suitable surfactants facilitates a discontinuous liquid exchange in CPC, enabling the cement setting reaction to take place. This paper reports on the use of these novel cement paste formulations as a controlled release system of antibiotics (gentamicin, vancomycin). Cement pastes were applied either as a one-component material, in which the solid drugs were physically dispersed, or as a two-component system, where the drugs were dissolved in an aqueous phase that was homogeneously mixed with the cement paste using a static mixing device during injection. Drug release profiles of both antibiotics from pre-mixed one- and two-component cements were characterized by an initial burst release of ∼7-28%, followed by a typical square root of time release kinetic for vancomycin. Gentamicin release rates also decreased during the first days of the release study, but after ∼1 week, the release rates were more or less constant over a period of several weeks. This anomalous release kinetic was attributed to participation of the sulfate counter ion in the cement setting reaction altering the drug solubility. The drug-loaded cement pastes showed high antimicrobial potency against Staphylococcus aureus in an agar diffusion test regime, while other cement properties such as mechanical performance or phase composition after setting were only marginally affected.

Properties of injectable ready-to-use calcium phosphate cement based on water-immiscible liquid

Calcium phosphate cements (CPCs) are highly valuable materials for filling bone defects and bone augmentation by minimal invasive application via percutaneous injection. In the present study some key features were significantly improved by developing a novel injectable ready-to-use calcium phosphate cement based on water-immiscible carrier liquids. A combination of two surfactants was identified to facilitate the targeted discontinuous exchange of the liquid for water after contact with aqueous solutions, enabling the setting reaction to take place at distinct ratios of cement components to water. This prolonged the shelf life of the pre-mixed paste and enhanced reproducibility during application and setting reactions. The developed paste technology is applicable for different CPC formulations. Evaluations were performed for the formulation of an α-TCP-based CPC as a representative example for the preparation of injectable pastes with a powder-to-carrier liquid ratio of up to 85:15. We demonstrate that the resulting material retains the desirable properties of conventional CPC counterparts for fast setting, mechanical strength and biocompatibility, shows improved cohesion and will most probably show a similar degree of resorbability due to identical mineral structure of the set products.

Systemic shRNA mediated knock down of S100A4 in colorectal cancer xenografted mice reduces metastasis formation

The metastasis-inducing protein S100A4 was found to be a prognostic indicator for the development of metachronous metastases. S100A4 expression levels correlate with the formation of human colorectal cancer metastases and shorter patients’ survival. Inhibition of S100A4 expression in patients might therefore result in decreased metastasis formation and prolonged survival. In the present study, we used shRNA expression plasmids to inhibit S100A4 expression in the colorectal cancer cell lines HCT116, SW620 and DLD-1. Cell lines with reduced S100A4 expression showed reduced cell migration and invasion in vitro. The knock-down of S100A4 expression also led to significantly diminished formation of liver metastases when intrasplenically transplanted in mice (P = 0.004). We then focused on the therapeutic potential of systemically applied shRNA expression plasmids acting on S100A4 via repeated hydrodynamics-based tail vein injection of plasmid DNA. Mice, intrasplenically transplanted with HCT116 cells and treated systemically with S100A4-shRNA plasmids, showed a decrease of S100A4 and MMP9 expression levels, resulting in significantly reduced liver metastases (P = 0.005). In summary, we show for the first time the intratumoral knock-down of S100A4 via systemic application of S100A4-shRNA plasmid DNA, which restricts metastasis formation in a xenografted mouse model of colorectal cancer.

Anti-Proliferative Efficacy of Icariin on HepG2 Hepatoma and Its Possible Mechanism of Action

The aim of the present work was to explore the anti-hepatoma effects of icariin both in vitro and in vivo and to elucidate its potential mechanism of action. The MTT assay was applied to test the anti-proliferative effects of icariin in vitro. HepG2 bearing NMRI nu/nu mice were used to test the anticancer effects of icariin in vivo. Immunohistochemical assay and flow cytometry assay (FACS) were applied to detect the possible mechanisms of action of icariin. MTT assay illustrated that icariin inhibited the proliferation of HepG2 cells in a concentration dependent manner; meanwhile, icariin inhibited the tumor growth in HepG2 bearing NMRI nu/nu mice. The tumor weight was inhibited by 55.6% and tumor volume was inhibited by 47.2%. Icariin did not influence the spleen and body weights or blood parameters. Immunohistochemical analysis indicated that the expressions of both CD31 and Ki67 in the icariin treated group were significantly lower than those in the control group (p < 0.01). FACS assay showed that icariin dramatically decreased the percentage of CD4+ and CD8+ cells in bone marrow and CD19+ cells in blood on day 8. On day 17, the percentage of CD8+ cells in blood was lower than those in the control group. CD4/CD8 ratio in icariin group was significantly elevated in bone marrow on day 17. Icariin showed anticancer efficacy both in vitro and in vivo. The possible mechanism of action could be related to its anti-angiogenesis and anti-proliferative effects in tumors.

Treatment of experimental brain metastasis with MTO-liposomes: impact of fluidity and LRP-targeting on the therapeutic result

PURPOSE

To test targeted liposomes in an effort to improve drug transport across cellular barriers into the brain.

METHODS

Therefore we prepared Mitoxantrone (MTO) entrapping, rigid and fluid liposomes, equipped with a 19-mer angiopeptide as ligand for LDL lipoprotein receptor related protein (LRP) targeting.

RESULTS

Fluid, ligand bearing liposomes showed in vitro the highest cellular uptake and transcytosis and were significantly better than the corresponding ligand-free liposomes and rigid, ligand-bearing vesicles. Treatment of mice, transplanted with human breast cancer cells subcutaneously and into the brain, with fluid membrane liposomes resulted in a significant reduction in the tumor volume by more than 80% and in a clear reduction in drug toxicity. The improvement was mainly depended on liposome fluidity while the targeting contributed only to a minor degree. Pharmacokinetic parameters were also improved for liposomal MTO formulations in comparison to the free drug. So the area under the curve was increased and t(1/2) was extended for liposomes.

CONCLUSION

Our data show that it is possible to significantly improve the therapy of brain metastases if MTO-encapsulating, fluid membrane liposomes are used instead of free MTO. This effect could be further enhanced by fluid, ligand bearing liposomes.

Novel Clostridium perfringens enterotoxin suicide gene therapy for selective treatment of claudin-3- and -4-overexpressing tumors

Bacterial toxins are known to be effective for cancer therapy. Clostridium perfringens enterotoxin (CPE) is produced by the bacterial Clostridium type A strain. The transmembrane proteins claudin-3 and -4, often overexpressed in numerous human epithelial tumors (for example, colon, breast, pancreas, prostate and ovarian), are the targeted receptors for CPE. CPE binding to them triggers formation of membrane pore complexes leading to rapid cell death. In this study, we aimed at selective tumor cell killing by CPE gene transfer. We generated expression vectors bearing the bacterial wild-type CPE cDNA (wtCPE) or translation-optimized CPE (optCPE) cDNA for in vitro and in vivo gene therapy of claudin-3- and -4-overexpressing tumors. The CPE expression analysis at messenger RNA and protein level revealed more efficient expression of optCPE compared with wtCPE. Expression of optCPE showed rapid cytotoxic activity, hightened by CPE release as bystander effect. Cytotoxicity of up to 100% was observed 72 h after gene transfer and is restricted to claudin-3-and -4-expressing tumor lines. MCF-7 and HCT116 cells with high claudin-4 expression showed dramatic sensitivity toward CPE toxicity. The claudin-negative melanoma line SKMel-5, however, was insensitive toward CPE gene transfer. The non-viral intratumoral in vivo gene transfer of optCPE led to reduced tumor growth in MCF-7 and HCT116 tumor-bearing mice compared with the vector-transfected control groups. This novel approach demonstrates that CPE gene transfer can be employed for a targeted suicide gene therapy of claudin-3- and -4-overexpressing tumors, leading to the rapid and efficient tumor cell killing in vitro and in vivo.

Novel effect of antihelminthic Niclosamide on S100A4-mediated metastatic progression in colon cancer

BACKGROUND

Metastasis formation in colon cancer severely reduces the survival rate in patients. S100A4, a calcium-binding protein, is implicated in promoting metastasis formation in colon cancer.

METHODS

To identify a transcription inhibitor of S100A4, high-throughput screening of 1280 pharmacologically active compounds was performed using a human colon cancer cell line expressing a S100A4 promoter-driven luciferase (LUC) reporter gene construct (HCT116-S1004p-LUC). Niclosamide, an antihelminthic agent, was identified as a potential candidate. Colon cancer cell lines (HCT116, SW620, LS174T, SW480, and DLD-1) were treated with 1 μM niclosamide to analyze the effect on S100A4 mRNA and protein expression by quantitative reverse transcription-polymerase chain reaction and immunoblot assays, and effects on cell migration, invasion, proliferation, and colony formation were also assessed in vitro. The effect of niclosamide on liver metastasis was assessed in a xenograft mouse model of human colon cancer (n = 8 mice) by in vivo imaging. The long-term effect of niclosamide on metastasis formation after discontinued treatment was quantified by scoring, and overall survival (n = 12 mice) was analyzed by Kaplan-Meier method after discontinuation of treatment. All statistical tests were two-sided.

RESULTS

Reduced S100A4 mRNA and protein expression, and inhibited cell migration, invasion, proliferation, and colony formation were observed in niclosamide-treated colon cancer cells in vitro. In vivo imaging of niclosamide-treated mice showed reduced liver metastasis compared with solvent-treated control mice (n = 4 mice per group). Compared with the control group, discontinuation of treatment for 26 days showed reduced liver metastasis formation in mice (n = 6 mice per group) (control vs discontinuous treatment, mean metastasis score = 100% vs 34.9%, mean difference = 65.1%; 95% confidence interval [CI] = 18.4% to 111.9%, P < .01) and increased overall survival (n = 6 mice per group; control vs discontinuous treatment, median survival = 24 vs 46.5 days, ratio = 0.52, 95% CI = 0.19 to 0.84, P = .001).

CONCLUSION

Niclosamide inhibits S100A4-induced metastasis formation in a mouse model of colon cancer and has therapeutic potential.

Sagopilone crosses the blood-brain barrier in vivo to inhibit brain tumor growth and metastases

The aim of this study was to determine the efficacy of sagopilone (ZK-EPO), a novel epothilone, compared with other anticancer agents in orthotopic models of human primary and secondary brain tumors. Autoradiography and pharmacokinetic analyses were performed on rats and mice to determine passage across the blood-brain barrier and organ distribution of sagopilone. Mice bearing intracerebral human tumors (U373 or U87 glioblastoma, MDA-MB-435 melanoma, or patient-derived non-small-cell lung cancer [NSCLC]) were treated with sagopilone 5-10 mg/kg, paclitaxel 8-12.5 mg/kg (or temozolomide, 100 mg/kg) or control (vehicle only). Tumor volume was measured to assess antitumor activity. Sagopilone crossed the blood-brain barrier in both rat and mouse models, leading to therapeutically relevant concentrations in the brain with a long half-life. Sagopilone exhibited significant antitumor activity in both the U373 and U87 models of human glioblastoma, while paclitaxel showed a limited effect in the U373 model. Sagopilone significantly inhibited the growth of tumors from CNS metastasis models (MDA-MB-435 melanoma and patient-derived Lu7187 and Lu7466 NSCLC) implanted in the brains of nude mice, in contrast to paclitaxel or temozolomide. Sagopilone has free access to the brain. Sagopilone demonstrated significant antitumor activity in orthotopic models of both glioblastoma and CNS metastases compared with paclitaxel or temozolomide, underlining the value of further research evaluating sagopilone in the treatment of brain tumors. Sagopilone is currently being investigated in a broad phase II clinical trial program, including patients with glioblastoma, NSCLC, breast cancer, and melanoma.

Early macrophage and cytokine response during the growth of immunogenic and non-immunogenic murine tumors

Very little data exist on the mechanisms of innate immunity during the first days after syngeneic tumor inoculation. Nonspecific macrophage reaction precedes the development of specific immune response and is important for further tumor growth and stroma formation. We investigated two lymphoma cell lines of the same origin, differing in immunogenicity: non-immunogenic parental strain P388 and its highly immunogenic subline P388/adria. Early systemic inflammatory response resulted in the enhancement of nitric oxide (NO) and superoxide production by peritoneal macrophages which was at a maximum on the first day after s.c. tumor inoculation and was observed in mice bearing either of these tumors independently of immunogenicity. It was followed by a transient elevation of the serum levels of pro-inflammatory cytokines: TNF-alpha IL-6. In order to evaluate the role of inflammatory response, vaccinations with lethally irradiated lymphoma cells were performed. After two weekly injections, the mice were challenged s.c. with live tumor cells of the same subline. Effective vaccination with P388/adria lymphoma cells induced retardation of tumor growth in parallel with down-regulation of peritoneal macrophage activity and abrogation of serum cytokine release. Non-effective immunization with P388 cells influenced neither tumor growth nor macrophage functions and cytokine level. Thus, a positive correlation was found between down-regulation of the inflammatory response and inhibition of tumor growth. We suppose that, in efficiently immunized mice, special mechanisms exist which are responsible for down-regulation of the inflammatory reaction. Macrophage products may facilitate tumor cell survival by preventing apoptosis or participate in the activation of tumor neoangiogenesis. Suppression of these activities may serve as an important tool for the inhibition of tumor growth at the early stages of malignant transformation.

Nonviral in vivo gene delivery into tumors using a novel low volume jet-injection technology

The jet-injection technology has developed as an applicable alternative to viral or liposomal gene delivery systems. In this study a novel, low-volume, 'high-speed jet injector' hand-held system was used for the direct gene transfer of naked DNA into tumors. Lewis-lung carcinoma bearing mice were jet-injected with the beta-galactosidase (LacZ), the green fluorescence (GFP) or the human tumor necrosis factor alpha (TNF-alpha) gene carrying vector plasmids. The animals received five jet injections into the tumor at a pressure of 3.0 bar, delivering 3--5 microl plasmid DNA (1 microg DNA/microl in water) per single jet injection. The jet injection of DNA leads to a widespread expression pattern within tumor tissues with penetration depths of 5--10 mm. Analysis of tumor cryosections revealed moderate LacZ or GFP expression at 48 h and strong reporter gene expression 72 h and 96 h after jet injection. The simultaneous jet injection of the TNF-alpha and LacZ carrying vectors demonstrated efficient expression and secretion of both the cytokine, as well as LacZ expression within the tumor 24 h, 48 h, 72 h, 96 h and 120 h after jet injection. These studies demonstrate the applicability of jet injection for the efficient in vivo gene transfer into tumors for nonviral gene therapy of cancer using minimal amounts of naked DNA.

Expression of CD44 isoforms in human breast carcinoma xenografts is not influenced by the treatment of mice with cytostatics or (anti-)hormones

CD44 standard (s) and variant (v) isoforms have been discussed to be implicated in progression and metastasis of different malignomas. For breast carcinomas, the results of different studies are contradictory. These apparent discrepancies suggest that CD44 isoforms are not available on the tumour cell surface, but could be regulated by different endogenous and exogenous factors. Here we report the regulation of CD44 isoforms in xenografted breast cancer cell lines by cytostatics, hormones and antihormones. The human breast cancer models MDA-MB 435, MCF-7, NCI/ADR, 4296, 4151 and 4134 were transplanted into the mammary fat pad of nude mice. When tumours reached a palpable size, animals were treated with farmorubicine, cyclophosphamide, estradiol, tamoxifen or progesterone, respectively. At different times after treatment, serum and tumours were taken. The expression of CD44 and its isoforms was determined by immunohistochemistry and RT-PCR, serum levels were measured by human specific ELISA kits. Serum levels of CD44s and v6 varied among the tumours. For 3/6 tumours we found differences between control groups and treated animals. Immunohistochemical results remained unchanged: each tumour showed a specific pattern of CD44 expression, but this pattern did not change when the animals received cytostatics, hormones or antihormones. The same held true for RT-PCR-results. Also, the time of tumour collection had no influence on CD44 expression. Therefore, it can be concluded, that in the xenografted breast cancer cell lines a regulation of CD44 isoforms by farmorubicine, cyclophosphamide, estradiol, progesterone or tamoxifen could not be found, while serum levels were influenced in some cases probably due to tumour cell kill and shedding of surface proteins into blood stream.

Development and characterisation of novel human multidrug resistant mammary carcinoma lines in vitro and in vivo

Clinical chemotherapy of breast carcinomas must be considered insufficient, mainly due to the appearance of drug resistance. The multidrug resistance (MDR) phenotype, either intrinsically occurring or acquired, e.g., against a panel of different antineoplastic drugs, is discussed in relation to several MDR-associated genes such as the MDR-gene mdr1 encoding the P-glycoprotein (PGP), the MRP gene (multidrug resistance protein) encoding an MDR-related protein or the LRP gene encoding the lung resistance protein. Numerous experimental and clinical approaches aiming at reversing resistance require well-characterised in vitro and in vivo models. The aim of our work was to develop multidrug resistant sublines from human xenotransplanted breast carcinomas, in addition to the broadly used line MCF-7 and its multidrug resistant subline MCF-7/AdrR. MDR was induced in vitro with increasing concentrations of Adriablastin (ADR) for several weeks, resulting in a 3.5- to 35-fold increase in IC50 values using the MTT-test. Cell lines were cross-resistant toward another MDR-related drug, vincristine, but remained sensitive to non-MDR-related compounds such as cisplatin and methotrexate. The resistance toward Adriamycin and vincristine was confirmed in vivo by a lack of tumour growth inhibition in the nude mouse system. Gene expression data for the mdr1/PGP, MRP/MRP and LRP/LRP on both the mRNA (RT-PCR) and the protein levels (immunoflow cytometry) demonstrated that induction of mdr1 gene expression was responsible for the acquired MDR phenotype. Rhodamine efflux data, indicated by PGP overexpression, underlined the development of this MDR mechanism in the newly established breast carcinoma lines MT-1/ADR, MT-3/ADR and MaTu/ADR.

Effects of amifostine (WR-2721, ethyol) on tumor growth and pharmacology of cytotoxic drugs in human xenotransplanted neuroblastomas

Amifostine was developed as a radio- and chemoprotective agent. It has shown protection against whole-body irradiation, and myelo- and nephrotoxicity of cytotoxic agents both in experimental and clinical studies. Some experimental trials revealed an influence of amifostine on tumor growth or the activity of cytotoxic drugs under certain circumstances. Therefore, it was the aim of our work to evaluate the pharmacological potential of amifostine in a preclinical in vivo situation with human xenotransplanted neuroblastomas. Human neuroblastoma cells (IMR5-75 and Kelly) were grown s.c. as xenografts in nude mice to palpable sizes (approximately 4 x 5 mm). Then the animals received 200 mg/kg amifostine i.p. and were treated 30 min later with one of the following cytotoxic drugs: cyclophosphamide, doxorubicin, cisplatin, ifosfamide, vincristine and etoposide. Amifostine as the only treatment did not influence the growth of the neuroblastomas IMR5-75 and Kelly. We observed no side effects of the compound itself. In no case did amifostine interact significantly with the antitumor effect of any cytostatic used in combination. However, amifostine mitigated the body weight loss induced by vicristine and the leukopenia induced by cyclophosphamide, cisplatin or ifosfamide, respectively. The side effects of the remaining cytostatics were--if observed at all--unchanged. We conclude that amifostine did not influence the tumor growth of xenotransplanted neuroblastomas and did not reduce the antineoplastic activity of the tested cytostatic drugs. Further investigation of amifostine as a protectant from side effects of chemotherapy in a clinical setting is warranted.

Involvement of macrophages and cytokines into rejection mechanism of the drug-resistant and immunogenic murine lymphoma P388/adria

Macrophages and their products may exert either inhibitory or stimulatory effects on malignant cells,thus preventing or supporting tumor growth, however, the mechanisms of this interaction are not fully understood. It was the aim of the present study to elucidate the role of macrophage activation during the growth and rejection of highly immunogenic murine leukemia P388/adria cell line which was made resistant by suboptimal treatment of mice with adriablastin during the serial passaging of parental P388 cells. The functional activity of peritoneal macrophages and the serum level of cytokines IL-1 beta, IL-6 and TNF-alpha were studied in different groups of mice. Mice from group 1 (control) received saline. Mice from group 2 (tumor bearers) with fast subcutaneous (s.c) 100% tumor growth were compared with animals from group 3 that had been twice previously immunized with lethally irradiated P388/adria cells and later inoculated with viable tumor cells. Tumors grew in only 25% of group 3 animals with a significant delay. The activity of peritoneal macrophages was studied by NO2- production and the NBT-test. Both tests revealed the early high systemic activation of macrophages in group 2. This coincided with the elevation of serum TNF-alpha and IL-6 levels. This effect was not dependent on whether alive or lethally irradiated tumor cells were inoculated. The NO2- production by peritoneal macrophages correlated well with the dynamics of serum cytokine levels while the NBT-test did not. Studies on group 3 showed total abrogation of early macrophage and cytokine reactions. The production of inhibitory factors by macrophages in previously immunized mice is suggested. The fact that the early activation of macrophages and increase of serum levels of proinflammatory cytokines occurred in animals with fast growing tumors, which was decreased or absent in animals with tumor delay or rejections, allows us to suppose that this reaction plays more a supporting than a protecting role for tumor growth.

In vivo characterization of immunogenicity of a mitoxantrone-resistant murine P388 leukemia

The Mitoxantrone-resistant murine leukemia P388/Mitox, expressing the multidrug-resistant phenotype, has a higher immunogenicity than the parent sensitive P388. This could be shown in vivo by immunization with lethally-irradiated tumor cells. If the P388/Mitox was used for immunization before subsequent challenge with viable tumor cells of the same line, this resulted in a partial rejection of tumors and production of a substantial number of tumor-free survivors. For an effective immunization at least two primings s.c., i.v. or i.p. with at least 10(6) irradiated cells were necessary. This protected the recipient mice from a challenge of up to 10(8) viable cells over a period of at least 75 days. Treatment of BDF1 mice with the T-cell suppressor Cyclosporin A prevents immunization. In nude mice no immunization effect could be obtained. It was possible to transfer immunity adoptively with spleen cells from mice, which were treated with irradiated tumor cells of the P388/Mitox line. Treatment of tumor-bearing mice with IL-2 resulted in a prolongation of survival both when it was administered prophylactically before transplantation of P388/Mitox and at an advanced stage (day 7-11). Also the alkyl-phosphocholine hexadecylphosphocholine was significantly effective in the resistant but not in the parent P388 leukemia. The data presented demonstrate that by development of a multidrug-resistance, concomitantly a xenogenization must have taken place which leads to a recognition of cells by immune mechanisms. In our model, T-lymphocytes and NK-/LAK-cells probably play a role in the immunologically conditioned rejection of tumor cells of the P388/Mitox leukemia.(ABSTRACT TRUNCATED AT 250 WORDS)

In vivo distribution and antitumour activity of liposomal 3',5'-O-dipalmitoyl-5-fluoro-2'-deoxyuridine

3',5'-O-dipalmitoyl-5-fluoro-2'-deoxyuridine (FUdR-dipalmitate), a lipophilic prodrug of 5-fluoro-2'-deoxyuridine (FUdR), was incorporated in different types of liposomes. The in vivo distribution and intrahepatic deacylation of liposomal FUdR-dipalmitate was found to be strongly dependent on liposome composition and on drug to lipid ratio. The use of fluid-type liposomes (egg PC/PS/CHOL) rendered FUdR-dipalmitate more susceptible to enzymatic breakdown than solid-type liposomes (DSPC/DPPG/CHOL). A decrease of the retention of the drug in the body was also obtained when FUdR-dipalmitate was incorporated in solid-type liposomes with high drug to lipid ratio (1:10) than with low ratio (1:50). In spite of these substantial differences in the rates at which FUdR was liberated from liposomes with different fluidity, size, or drug to lipid ratio, only minor differences in therapeutic effect were observed in a number of murine tumour models (P388 leukaemia, Lewis Lung carcinoma, B16 melanoma and a C26 adenocarcinoma liver metastasis model). The lipophilic prodrug of FUdR exhibited antitumour activity at 100-600 times lower doses than the free drug. However, at these therapeutic doses FUdR-dipalmitate was also far more toxic. This prohibited the use of higher doses to increase antitumour activity.

Development of a mitoxantrone-resistant P 388 in vivo: approaches to overcome resistance

A normally, relatively sensitive P 388 developed resistance within few passages (P 388/Mitox) by in vivo treatment with suboptimal doses (1 mg/kg i.v.) of mitoxantrone. This resistance remained stable over 50 generations without further drug treatment. Immunization with irradiated cells (30 Gy) 7 days before tumor challenge led to partial rejection, proving that there was a higher immunogenicity of the resistant line in comparison to the parenteral P 388 line. The P 388/Mitox showed cross-resistance towards doxorubicin, daunorubicin and vincristine. Cis-DDP and bleomycin had in the resistant line significantly better antineoplastic efficacy than in the source P 388 and should be taken into consideration as second-line therapy following development of clinical mitoxantrone resistance. Nifedipine, a calcium channel blocker, and the immunosuppressive agent ciclosporin A were able to overcome resistance partially, but the mechanisms are still unclear. The P 388/Mitox can be considered as an interesting in vivo model for further research concerning resistance mechanisms and reversal of resistance.