[Measuring 14C-glucose and 14C-acetate oxidation in tumour cells and tumorous host organism]. / A bioenergetikai profil vizsgálata 14C-glükóz és 14C-acetát oxidációjának összehasonlításával tumorsejtekben és tumoros szervezetben.

Tumour cell metabolism can be influenced by alterations of the extracellular microenvironment and the tumour-promoting genetically changed mechanisms. There is increasing interest to introduce appropriate bioenergetic assays to describe the therapeutic effect and metabolic subtypes of tumours in clinical oncology. The analysis of 14C-glucose and 14C-acetate oxidation could be a suitable method to examine the metabolic/bioenergetic profiles of tumour cells and tumorous host organisms. The metabolic activity of tumour cells (in vitro cell lines, primary human lymphocytes and leukaemia cells) and the tumourous host organism were examined in vitro and in vivo by detecting the released CO2 levels derived from the radioactive carbon atom labelled energy substrates. We have found that the most cancer cells of solid tumours oxidised glucose more intensively than acetate. It was interesting that AML, CML and CLL cells isolated from blood preferred acetate as an energy substrate in vitro. Furthermore, based on our observations, tumours affected the glucose or acetate oxidation of the organism when applying bioenergetic substrates per os or iv. We provided the first data about the alterations in metabolic profiles of the tumour bearing organism in xenograft models. In summary, according to our results, comparison of the energy substrate oxidation can be an indicative method related to the metabolic profile analysis of tumour cells in vitro and tumorous host organism in vivo.

Optimization of adiponectin-derived peptides for inhibition of cancer cell growth and signaling.

Adiponectin, an adipose tissue-excreted adipokine plays protective roles in metabolic and cardiovascular diseases and exerts anti-cancer activities, partially by interfering with leptin-induced signaling. Previously we identified the active site in the adiponectin protein, and generated both a nanomolar monomeric agonist of the adiponectin receptor (10-mer ADP355) and an antagonist (8-mer ADP400) to modulate various adiponectin receptor-mediated cellular functions. As physiologically circulating adiponectin forms multimeric complexes, we also generated an agonist dimer with improved biodistribution and in vitro efficacy. In the current report, we attempted to optimize the monomeric agonist structure. Neither extension of the peptide up to 14-mer analogs nor reinstallation of native residues in permissible positions enhanced significantly the activity profile. The only substitutions that resulted in 5-10-fold improved agonistic activity were the replacement of turn-forming Gly4 and Tyr7 residues with Pro and Hyp, respectively, yielding the more active native ß-sheet structure. All peptides retained good stability in human serum exhibiting half-lives >2 h. The cellular efficacy and stability rankings among the peptides followed expected structure-activity relationship trends. To investigate whether simultaneous activation of adiponectin pathways and inhibition of leptin-induced signals can result in cytostatic and anti-oncogenic signal transduction processes, we developed a chimera of the leptin receptor antagonist peptide Allo-aca (placed to the N-terminus) and ADP355 (at the C-terminus). The in vitro anti-tumor activity and intracellular signaling of the chimera were dominated by the more active Allo-aca component. The ADP355 part, however, reversed unfavorable in vivo metabolic effects of the leptin receptor antagonist.

Development of second generation peptides modulating cellular adiponectin receptor responses.

The adipose tissue participates in the regulation of energy homeostasis as an important endocrine organ that secretes a number of biologically active adipokines, including adiponectin. Recently we developed and characterized a first-in-class peptide-based adiponectin receptor agonist by using in vitro and in vivo models of glioblastoma and breast cancer (BC). In the current study, we further explored the effects of peptide ADP355 in additional cellular models and found that ADP355 inhibited chronic myeloid leukemia (CML) cell proliferation and renal myofibroblast differentiation with mid-nanomolar IC50 values. According to molecular modeling calculations, ADP355 was remarkably flexible in the global minimum with a turn present in the middle of the peptide. Considering these structural features of ADP355 and the fact that adiponectin normally circulates as multimeric complexes, we developed and tested the activity of a linear branched dimer (ADP399). The dimer exhibited approximately 20-fold improved cellular activity inhibiting K562 CML and MCF-7 cell growth with high pM-low nM relative IC50 values. Biodistribution studies suggested superior tissue dissemination of both peptides after subcutaneous administration relative to intraperitoneal inoculation. After screening of a 397-member adiponectin active site library, a novel octapeptide (ADP400) was designed that counteracted 10-1000 nM ADP355- and ADP399-mediated effects on CML and BC cell growth at nanomolar concentrations. ADP400 induced mitogenic effects in MCF-7 BC cells perhaps due to antagonizing endogenous adiponectin actions or acting as an inverse agonist. While the linear dimer agonist ADP399 meets pharmacological criteria of a contemporary peptide drug lead, the peptide showing antagonist activity (ADP400) at similar concentrations will be an important target validation tool to study adiponectin functions.

Determination of energy metabolites in cancer cells by porous graphitic carbon liquid chromatography electrospray ionization mass spectrometry for the assessment of energy metabolism.

A high performance liquid chromatography (HPLC) tandem mass spectrometric (MS/MS) method has been developed for the simultaneous determination of fifteen glucose, or acetate derived metabolites isolated from tumor cells. Glycolytic and tricarboxylic acid (TCA) cycle metabolites as well as acidic amino acids were separated on a HPLC porous graphitic carbon (PGC) column and simultaneously determined by means of triple quadrupole MS/MS using multiple reaction monitoring (MRM). Target compounds were eluted within 10 min with 8% v/v formic acid as an electronic modifier added to a 4:1 v/v methanol water mobile phase. The calibration is linear in the 1-100 µM concentration range for each analyte. The limit of detection ranges between 0.39 and 2.78 µM for the analytes concerned. To test the PGC-HPLC-MS/MS method in metabolomic studies, ZR-75.1 human mammary adenocarcinoma cells were labeled with U-(13)C glucose or 1-(13)C acetate. Applying the MRM mode, the incorporation of (13)C into metabolites, isolated from the tumor cells, and derived from glucose or acetate, could be properly identified.

Efficacy of a leptin receptor antagonist peptide in a mouse model of triple-negative breast cancer.

Triple-negative breast cancers, which represent 10-20% of all mammary tumours, are characterised by the aggressive phenotype, are often found in younger women and have been associated with poor prognosis. Obesity increases the risk for triple-negative breast cancer development. Because triple-negative breast cancer patients are unresponsive to current targeted therapies and other treatment options are only partially effective, new pharmacological modalities are urgently needed. Here we examined if the leptin (obesity hormone) receptor is a viable target for the treatment of this cancer subtype. In human triple-negative breast cancer tissues, the leptin receptor was expressed in 92% (64/69) and leptin in 86% (59/69) of cases. In a model triple-negative breast cancer cell line MDA-MB-231, the leptin receptor antagonist peptide Allo-aca inhibited leptin-induced proliferation at 50 pM concentration. In an MDA-MB-231 orthotopic mouse xenograft model, Allo-aca administered subcutaneously significantly extended the average survival time from 15.4 days (untreated controls) to 24 and 28.1 days at 0.1 and 1mg/kg/day doses, respectively. In parallel, conventional treatment with 1mg/kg/day intraperitoneal cisplatin prolonged the average survival time to 18.6 days, while administration of 20mg/kg/day oral Tamoxifen (negative control) had no significant survival effects relative to controls. In normal CD-1 mice, Allo-aca produced no systemic toxicity up to the highest studied subcutaneous bolus dose of 50mg/kg, while, as expected, it induced a modest 6-10% body weight increase. Our results indicate that leptin receptor antagonists could become attractive options for triple-negative breast cancer treatment, especially in the obese patient population.

Peptide-based leptin receptor antagonists for cancer treatment and appetite regulation.

Leptin, a multifunctional hormone, controls various processes in both the central nervous system and in peripheral tissues. Because of the presence of multiple leptin/receptor (ObR) interaction sites and diverse leptin activities, the literature lacks truly monofunctional leptin protein derivatives or fragments. To date, selective ObR antagonists have not been reported. We developed short, pharmacologically advantageous peptide analogs of ObR-binding site III of leptin that acted as selective ObR inhibitors without any partial agonistic activity. These reduced leptin-dependent growth and signaling in cancer cell lines at picomolar and low nanomolar concentrations. In immunocompromised mice the peptides suppressed the growth of rapidly proliferating orthotopic human breast cancer xenografts by 50% when administered either intraperitoneally (i.p.) or subcutaneously (s.c.) for 38 days at a 0.1 mg/kg/day dose. The peptides were distributed to the brain, and when added to growing C57BL/6 normal mice i.p., s.c., or orally, the lead antagonist accelerated normal weight increase without producing any toxic effects. Weight gain increases could not be observed after 10-12 days of treatment indicating that the mice became resistant to the central nervous system activity of leptin antagonists. However, in normal growing rats the intranasal administration at 0.1 mg/kg/day for 20 days resulted in a 2% net total body weight gain without signs of resistance induction. In addition to the potential of these peptides in drug development against primary and metastatic tumors and cachexia, our data confirm that resistance to leptin resides at the blood-brain barrier.

Differential inhibition of single and cluster type tumor cell migration.

For the control of tumor metastasis it is important to identify chemical compounds with antimigratory potency. Agents acting against single cell and cluster type migration are necessary for successful antimetastatic therapy. In the present study, the migration of HT-1080 fibrosarcoma cells and OSCORT osteosarcoma cells was compared in a Boyden chamber and in an extracellular matrix (ECM)-based three-dimensional cell culture (3-DCC) model system. The Boyden chamber offers a model of single tumor cell migration, whereas the 3-DCC model system demonstrates invasive growth in the form of a cluster. Since PD98059 (MEK inhibitor) exclusively reduced migration in the 3-DCC model, it may be plausible that the ERK/MAPK signaling pathway is essential for cluster type migration. Interestingly, single cell migration was stimulated upon blocking phosphatidylinositol 3-kinase (PI3K) and also p38-MAPK by treatment with LY294002 and SB203580 respectively. A remarkable reduction of single cell migration was observed following treatment with okadaic acid, a phosphatase 1 (PP1) and 2A (PP2A) inhibitor, which was rather intriguing. This study provided evidence that certain cytotoxic/cytostatic agents at appropriate concentrations were able to preferentially inhibit certain types of migration relative to cell proliferation. Single cell migration was selectively inhibited by taxol at very low subtoxic concentration, whereas 5-hexyl-2'-deoxyuridine (HUdR) exclusively inhibited the cluster type of migration. The borrelidin compound was able to inhibit both types of tumor cell migration, but single tumor cell migration was much less affected. It is interesting that migration was more reduced than proliferation by borrelidin, especially at the advanced growth stage. Taxol is recommended as an agent acting against single cell migration, as well as HUdR and borrelidin as leading compounds for developing antimetastatic drugs against cluster type migration.

Extracellular matrix induces doxorubicin-resistance in human osteosarcoma cells by suppression of p53 function.

BACKGROUND: Osteosarcoma is the most common primary malignant bone tumor in childhood and adolescence. The several chemotherapy-resistant cases of osteosarcoma are at a higher risk of relapse and adverse outcome. OBJECTIVE: The aim of the current study was to determine the role of extracellular matrix in the resistance developed against chemotherapeutic treatments of human osteosarcoma cells. MATERIALS AND METHODS: A cell line, named OSCORT was established from the biopsy of a 17-year-old male patient with primary osteosarcoma. Cell proliferation, apoptosis and quantification of DNA damage after treatments with doxorubicin were investigated in classical and three-dimensional cell culture systems using an extracellular matrix gel. The experimental results were related to the clinical observations of the case. RESULTS: The cells cultured in extracellular matrix gel have shown resistance to doxorubicin similar to that seen in the clinical case, as demonstrated by their proliferation, apoptosis and doxorubicin-induced DNA damage characteristics. Among the extracellular matrix components, the heparan sulfate proteoglycan and-to a lesser extent-fibronectin were involved in the doxorubicin resistance. Laminin and nidogen did not decrease the cytoreductive effect of doxorubicin, while collagen IV even increased it. The extracellular matrix gel decreased the protein levels of p53 and abrogated its cell nuclear translocalization. The most frequent known mutations in the p53 gene were not found in OSCORT cells. CONCLUSION: The current study provides experimental evidence for an epigenetical, extracellular matrix-induced loss of p53 function, which lead to a potent chemotherapy resistance showing accordance with the clinical experience.

[Study of drugs against neoplastic metastasis]. / A tumorok áttétképzését korlátozó hatóanyagok kutatása.

Further progress in the therapy of malignant diseases is expected from the introduction of potent antimetastatic drugs. Surveying of the complex and multi-step behavior of the metastatic process, compounds showing inhibitory action against tumor cell migration may be ranked among the promising antimetastatic agents. Our present study indicate, however, that the antimigratory actions of certain antitumor drugs (doxorubicin, taxol), and inhibitors of signal transduction (PD-98059, LY-294002, SB-203580) are highly dependent on the assay applied (Boyden-chamber, 3D ECM cell culture). It has been proposed that agents interrupting cell-extracellular matrix contacts (hexyldeoxyuridine, borrelidin) and others interfering with the regulatory mechanism of gene translation (rapamycin, ribavirin) could be regarded as leading compounds in the antimetastatic drug development process. Nevertheless, for introducing diagnostically based targeted therapy the forthcoming tasks must include the further elucidation of the molecular mechanisms implicated in the amoeboid and cluster type of cell migration.

Repopulation of osteosarcoma cells after treatment with doxorubicin in the presence of extracellular matrix biopolymers.

PURPOSE: To elucidate the role of extracellular matrix (ECM) in repopulation capacity of osteosarcoma cells after doxorubicin treatment. METHODS: OSCORT cells established in our laboratory from a human osteosarcoma, were treated with doxorubicin in monolayer for 4 h, then cells were further incubated either in monolayer or in ECM-containing three-dimensional cell-culture (3-DCC), apoptosis induction and changes in cell number were measured. Alkaline comet assay was applied to estimate DNA damage, immunoblot technique and immunocytochemistry were used to investigate p53 protein synthesis, and the repopulating capacity in monolayer culture and in ECM-based 3-DCC, after doxorubicin treatment was measured. In addition to OSCORT culture five other human cell lines (HT-1080, PC-3, MDA-MB231, A-431 and ZR-75-1) were used to compare the antimigratory and antiproliferative effects of doxorubicin. RESULTS: The apoptotic index, the extent of DNA damage and the representation of p53 were much lower in the OSCORT cell cultures if the cells were exposed to ECM after treatment with doxorubicin. The doxorubicin-treated OSCORT cells transferred from the monolayer culture were not able to proliferate at all, at the same time, the cytoprotection provided by ECM prevailed upon transferring the cells into plastic dish, and resulted in potent repopulation capacity of the cells. CONCLUSIONS: Present data indicate that ECM contributes to failure in therapy of human osteosarcoma in clinical situation. Overall, the application of ECM-based 3-DCC could be suggested as an appropriate model system for the better understanding of antitumor drug action and hereby to set the stage for promising novel pharmacological approaches in cancer therapy.

[Potentiation of 5-fluorouracil efficacy. Molecular mechanisms playing a role in the cytotoxic action of 5-fluorouracil and 5-ethyl-2'-deoxyuridine (EUdR) combination]. / Az 5-fluorouracil (5-FU) hatékonyságának fokozása. Az 5-FU és 5-etil-2'-dezoxiuridin (EUdR) kombináció hatásában szerepet játszó molekuláris tényezôk.

UNLABELLED: Pharmacologic modulation of 5-fluorouracil (5-FU) metabolism provides a possibility for the enhancement of its clinical efficacy. AIM: The purpose of the present work was to study the effect of 5-ethyl-2'-deoxyuridine (EUdR), a potent 5-FU modulator, on different molecular mechanisms, influenced by 5-FU itself, and to obtain further data about the mode of action of the combination. MATERIALS AND METHODS: SW620 cell line was used for the experiments. Cytotoxicity was studied by MTT test, cell kinetic changes by FACStar flow cytometer, apoptosis by fluorescent microscope after staining the cells with acridine orange and ethydium bromide, DNA fragmentation by PAGE electrophoresis after RNase and proteinase-K digestion, thymidine incorporation with 3H-thymidine, p53 and PCNA protein expression by Western blotting. RESULTS: The cytotoxicity of 5-FU was potentiated dose dependently by EUdR. One hundred muM concentration of EUdR resulted in a 40% decrease of the IC50 value of 5-FU. Cell cycle arrest in the G2/M transition phase was most pronounced after combined treatment with 5-FU+EUdR. EUdR potentiated the incorporation of 3Hthymidine into DNA. In addition to the increase of apoptosis rate, the expression of p53 protein, caused by 5-FU was further potentiated by UdR. CONCLUSION: This study demonstrated a potential novel approach to increase the efficacy of 5-FU by EUdR, which incorporated two complementary molecular actions, the selective modulation of TS inhibition and potentiation of the p53 protein expression, consequently leading to an increase in the apoptotic rate.

Thioacetamide-induced hepatic fibrosis in transforming growth factor beta-1 transgenic mice.

OBJECTIVE: Transforming growth factor beta-1 (TGF-beta 1) is thought to be one of the most important factors affecting the development of fibrotic processes in the liver. AIM: To discover whether endogenously higher TGF-beta 1 production influences the progression and reversibility of liver fibrosis in mice. METHOD: We compared thioacetamide-induced liver fibrosis between wild-type and transgenic mice overexpressing active TGF-beta 1 in the liver. Hepatic fibrosis was detected on histological sections, and fibrotic areas were measured by means of morphometric analysis. We also performed Northern blot hybridisation and gelatine zymography to improve our understanding of the process. RESULTS: The fibrotic process was faster in the transgenic animals, and regression after the withdrawal of the fibrogenic agent was slower. Fibrosis did not disappear completely from the TGF-beta 1 overexpressing mice, even at the endpoint of the experiment. CONCLUSION: Since the increased TGF-beta 1 production in the liver slowed down the regression of the liver fibrosis, the behaviour of these transgenic mice is more similar to the human situation, where cirrhosis is irreversible. We propose that this transgenic model is more suitable for investigating fibrotic liver diseases than the experiments done previously on wild-type rodents.