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.

SPON2, a newly identified target gene of MACC1, drives colorectal cancer metastasis in mice and is prognostic for colorectal cancer patient survival.

MACC1 (metastasis associated in colon cancer 1) is a prognostic biomarker for tumor progression, metastasis and survival of a variety of solid cancers including colorectal cancer (CRC). Here we aimed to identify the MACC1-induced transcriptome and key players mediating the MACC1-induced effects in CRC. We performed microarray analyses using CRC cells ectopically overexpressing MACC1. We identified more than 1300 genes at least twofold differentially expressed, including the gene SPON2 (Spondin 2) as 90-fold upregulated transcriptional target of MACC1. MACC1-dependent SPON2 expression regulation was validated on mRNA and protein levels in MACC1 high (endogenously or ectopically) and low (endogenously or by knockdown) expressing cells. Chromatin immunoprecipitation analysis demonstrated the binding of MACC1 to the gene promoter of SPON2. In cell culture, ectopic SPON2 overexpression induced cell viability, migration, invasion and colony formation in endogenously MACC1 and SPON2 low expressing cells, whereas SPON2 knockdown reduced proliferative, migratory and invasive abilities in CRC cells with high endogenous MACC1 and SPON2 expression. In intrasplenically transplanted NOD/SCID mice, metastasis induction was analyzed with control or SPON2-overexpressing CRC cells. Tumors with SPON2 overexpression induced liver metastasis (vs control animals without any metastases, P=0.0036). In CRC patients, SPON2 expression was determined in primary tumors (stages I-III), and survival time was analyzed by Kaplan-Meier method. CRC patients with high SPON2 expressing primary tumors demonstrated 8 months shorter metastasis-free survival (MFS) compared with patients with low SPON2 levels (P=0.053). Combining high levels of SPON2 and MACC1 improved the identification of high-risk patients with a 20-month shorter MFS vs patients with low biomarker expression. In summary, SPON2 is a transcriptional target of the metastasis gene MACC1. SPON2 induces cell motility in vitro and CRC metastasis in mice. In patients, SPON2 serves as prognostic indicator for CRC metastasis and survival, and might represent a promising target for therapeutic approaches.

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.

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.

Radiosensitisation of U87MG brain tumours by anti-epidermal growth factor receptor monoclonal antibodies.

As epidermal growth factor receptor (EGFR) has been reported to be a radiation response modulator, HER inhibitors are regarded to act as potential radiosensitisers. Our study examined the role of nimotuzumab and cetuximab both, the two monoclonal antibodies (mAbs) to EGFR, as radiosensitisers in a murine glioma model in vivo. Co-administration of both the antibodies with radiation increased the radiosensitivity of U87MG, resulting in a significant delay of subcutaneous (s.c.) tumour growth. Furthermore, the addition of antibodies to the radiation decreased brain tumour sizes and is inhibited by 40-80% the increased tumour cell invasion provoked by radiotherapy, although promoted tumour cell apoptosis. Whereas nimotuzumab led to a reduction in the size of tumour blood vessels and proliferating cells in s.c. tumours, cetuximab had no significant antiangiogenic nor antiproliferative activity. In contrast, cetuximab induced a more marked inhibition of EGFR downstream signalling compared with nimotuzumab. Moreover, both antibodies reduced the total number of radioresistant CD133+ cancer stem cells (CSCs). These results were encouraging, and showed the superiority of combined treatment of mAbs to EGFR and radiation over each single therapy against glioblastoma multiforme (GBM), confirming the role of these drugs as radiosensitisers in human GBM. In addition, we first showed the ability of mAb specifics against EGFR to target radioresistant glioma CSC, supporting the potential use in patients.

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.

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.

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)

Carboplatin-liposomes as activators of hematopoiesis.

Recombinant colony stimulating factors are studied in clinical trials with the purpose being the relief of the side effects of high dose chemotherapy and to make an optimized treatment regimen possible. The broad use of such factors is hindered by their relatively high costs, their short elimination half-lives, the occurrence of mild side effects, and the limitation of their action to the stimulation of mainly neutrophils. Therefore, exogenous preparations inducing an endogenous activation of hematopoiesis are being sought. In experiments in mice we have shown that carboplatin-liposomes injected intraperitoneally in a single dose of 100 mg/kg led to a strong two-peak increase in white blood cell counts. A maximum 10-fold elevation compared to controls of free carboplatin or empty liposomes was observed on day 2 and was probably due to the release and mobilization of cells from storage compartments. The second peak of about a 6-fold increase occurred on day 7-8 and can be seen as an indicator of bone marrow stimulation. Differentiation of blood cells revealed that neutrophils, lymphocytes and platelets multiplied. We presume that this effect of carboplatin-liposomes is due to a relatively fast uptake of these vesicles by macrophages as their natural target. Within these cells carboplatin is metabolized, leading to an almost total loss of antineoplastic activity against the murine P388 leukemia. Concomitantly, cytokines are apparently induced in and released from macrophages producing secondarily hematopoietic growth factors either directly or in combination with other cytokines. An involvement of macrophages is indicated by the fact that an intraperitoneal pretreatment of mice with zymosan caused a partial but significant suppression of hematopoietic stimulation. In an in vitro colony forming assay of serum of mice treated 1, 3, or 7 days with carboplatin-liposomes, the number of colonies increased 20-fold compared to serum from saline treated animals. Additionally, a combined intraperitoneal treatment of mice with 100 mg/kg of cyclophosphamide followed by carboplatin-liposomes one hour later demonstrated that prevention of cytostatic-induced leukopenia is possible by this method. Although the mechanism of stimulation of hematopoiesis by carboplatin-liposomes is still partially unknown our results suggest that there should be further development of such a preparation for possible use in the treatment of cancer or other inherited or acquired hematopoietic disorders.

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.

Determination of antineoplastic activity and toxicity of tumor necrosis factor (TNF) in animal experiments. Correlation to clinical findings.

Because of the deep evolutionary roots which macrophages and their products have, it should be possible to relate effects of the biological response modifier TNF observed in cancer patients with those determined in animal species. We have tested this hypothesis both with regard to antitumor efficacy and unwanted side-effects in murine tumor models. In the intramuscularly (i.m.) transplanted B16 melanoma, TNF had both after intratumoral (i.t.) and intravenous (i.v.) administration (qd 7-11, 14-17) a significant and dose-dependent effect on tumor growth. This effect was transitory and led only to a moderate increase in survival time of the animals. This correlates well with the also unsatisfactory clinical antineoplastic activity of TNF. From the measurement of body weight reduction, WBC counts, platelets, recalcification time, transaminases and body temperature in tumor bearing mice it can be concluded that there are close similarities to the side-effects observed in patients, although the level and/or time course of the noticed changes were differently expressed. In principle, it seems possible to predict clinical effects of biological response modifiers in animal experiments even if not all mechanisms are clearly understood.

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.