Biomedical subjects

S Orlowski

Publications and source records attributed to S Orlowski.

At least 19 recordsLinked to original sources

PubMed1999

Mechanisms of electrochemotherapy.

Electrochemotherapy is a new therapeutic approach providing delivery into cell interiors of nonpermeant drugs with intracellular targets. It is based on the local application of short and intense electric pulses that transiently permeabilize cells in tissues. To date, its main application has been the treatment of tumor nodules when the electric pulses are associated with nonpermeant drugs having high intrinsic cytotoxicity. The most convenient drug is bleomycin, a currently used anticancer drug, but cytotoxicity of cisplatin is also increased in vivo by means of this original drug delivery approach. The efficacy of this new method is based on the following mechanisms: (i) electropermeabilization of cells in tissues; (ii) use of nonpermeant drugs having a high intrinsic cytotoxicity; (iii) existence of vascular effects due to the permeabilizing electric pulses; (iv) complementary role of the host's immune system. Preclinical trials have shown the efficacy of this new therapeutic modality in various tumor models. Clinical trials are in progress, demonstrating its feasibility in humans as well as the interest of the method.

Journal Article↗

PubMed1999

Internalisation of the bleomycin molecules responsible for bleomycin toxicity: a receptor-mediated endocytosis mechanism.

Bleomycin (BLM) does not diffuse through the plasma membrane but nevertheless displays cytotoxic activity due to DNA break generation. The aim of the study was to describe the mechanism of BLM internalisation. We previously provided evidence for the existence of BLM-binding sites at the surface of DC-3F Chinese hamster fibroblasts, as well as of their involvement in BLM cytotoxicity on DC-3F cells and related BLM-resistant sublines. Here we report that A253 human cells and their BLM-resistant subline C-10E also possessed a membrane protein of ca. 250 kDa specifically binding BLM. Part of this C-10E cell resistance could be explained by a decrease in the number of BLM-binding sites exposed at the cell surface with respect to A253 cells. The comparison between A253 and DC-3F cells exposing a similar number of BLM-binding sites revealed that the faster the fluid phase endocytosis, the greater the cell sensitivity to BLM. Moreover, the experimental modification of endocytotic vesicle size showed that BLM cytotoxicity was directly correlated with the flux of plasma membrane area engulfed during endocytosis rather than with the fluid phase volume incorporated. Thus, BLM would be internalised by a receptor-mediated endocytosis mechanism which would first require BLM binding to its membrane receptor and then the transfer of the complex into intracellular endocytotic vesicles, followed by BLM entry into the cytosol, probably from a nonacidic compartment.

Animals↗

PubMed1998

Multidrug resistance transporter P-glycoprotein has distinct but interacting binding sites for cytotoxic drugs and reversing agents.

P-Glycoprotein, the plasma membrane protein responsible for the multidrug resistance of some tumour cells, is an active transporter of a number of structurally unrelated hydrophobic drugs. We have characterized the modulation of its ATPase activity by a multidrug-resistance-related cytotoxic drug, vinblastine, and different multidrug-resistance-reversing agents, verapamil and the dihydropyridines nicardipine, nimodipine, nitrendipine, nifedipine and azidopine. P-Glycoprotein ATPase activity was measured by using native membrane vesicles containing large amounts of P-glycoprotein, prepared from the highly multidrug-resistant lung fibroblasts DC-3F/ADX. P-Glycoprotein ATPase is activated by verapamil and by nicardipine but not by vinblastine. Among the five dihydropyridines tested, the higher the hydrophobicity, the higher was the activation factor with respect to the basal activity and the lower was the half-maximal activating concentration. The vinblastine-specific binding on P-glycoprotein is reported by the inhibitions of the verapamil- and the nicardipine-stimulated ATPase. These inhibitions are purely competitive, which means that the bindings of vinblastine and verapamil, or vinblastine and nicardipine, on P-glycoprotein are mutually exclusive. In contrast, verapamil and nicardipine display mutually non-competitive interactions. This demonstrates the existence of two distinct specific sites for these two P-glycoprotein modulators on which they can bind simultaneously and separately to the vinblastine site. The nicardipine-stimulated ATPase activity in the presence of the other dihydropyridines shows mixed-type inhibitions. These dihydropyridines have thus different binding sites that interact mutually to decrease their respective, separately determined affinities. This could be due to steric constraints between sites close to each other. This is supported by the observation that vinblastine binding is not mutually exclusive with nifedipine or nitrendipine binding, whereas it is mutually exclusive with nicardipine. Moreover, verapamil binding also interacts with the five dihydropyridines by mixed inhibitions, with different destabilization factors. On the whole our enzymic data show that P-glycoprotein has distinct but interacting binding sites for various modulators of its ATPase function.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1998

Bromocriptine modulates P-glycoprotein function.

The multidrug resistance (MDR)-associated P-glycoprotein (P-gp) is a membrane transporter which carries, at the expense of MgATP hydrolysis, many amphiphilic molecules, such as the MDR-related cytotoxic drugs vincristine and vinblastine, and the MDR-reversing agents verapamil and progesterone. We have tested the effects on P-gp function of bromocriptine (BCT), an ergot alkaloid known as a D2 dopaminergic receptor agonist. BCT (at 4 microM) partially reverses the P-gp-mediated vincristine resistance of the Chinese hamster lung fibroblasts DC-3F/ADX, a MDR cell line. P-gp containing membrane vesicles prepared from the DC-3F/ADX cells exhibit, in the absence of any added drug, a basal MgATPase activity due to P-gp. BCT inhibits this basal ATPase activity, with a half-inhibiting concentration of 0.30 +/- 0.15 microM. BCT also inhibits the verapamil-induced P-gp ATPase stimulation competitively (Ki approximately 0.2 microM), and the progesterone-induced P-gp ATPase stimulation non-competitively (Ki approximately 0.07-0.10 microM). BCT also non-competitively inhibits the vinblastine-dependent P-gp ATPase activity within the same concentration range. Hydroxylated metabolites of BCT have different effects on P-gp ATPase, only the monohydroxylated being able to modulate both the basal and the drug-stimulated ATPase activities. In conclusion, these effects of BCT on P-gp function can be linked to a specific interaction with P-gp, probably involving inhibition of P-gp-mediated drug transport.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1998

Electrochemotherapy on liver tumours in rabbits.

Electrochemotherapy (ECT) is a new therapeutic approach combining the effects of a low-permeant cytotoxic drug, bleomycin (BLM), administered i.v. and cell-permeabilizing electric pulses (EPs) locally delivered to tumours. The transient permeabilization of the cell membrane by the EPs allows free access of BLM to its intracellular targets, largely enhancing BLM's cytotoxic effects. ECT efficacy has been proved so far on transplanted subcutaneous murine tumours and on subcutaneous metastases in humans. Here, we present the first study of the effects of ECT on tumours transplanted to livers in rabbits. We used a recently developed EP applicator consisting of an array of parallel and equidistant needles to be inserted in tissues. Effects of EPs alone or of ECT were assessed by histological analysis, tumour growth rates and survival of the treated animals. A transient blood hypoperfusion was seen in the electropulsed areas, with or without BLM, related to EP-dependent vasoconstriction but this had no major effects on cell survival. Long-term effects depended on the presence of BLM at the time of EP delivery. Almost complete tumour necrosis was observed after ECT, resulting from both BLM direct cytotoxic effects on electropermeabilized tumour cells and indirect effects on the tumour vessels. A large reduction in tumour growth rate and significantly longer survival times were scored in comparison with control rabbits. Moreover, ECT of liver tumours was well tolerated and devoid of systemic side-effects. When ECT was associated with a local interleukin 2-based immunotherapy, increased local anti-tumour effectiveness as well as a large decrease in the number of metastases were observed. Thus, ECT could become a novel treatment modality for liver tumours and other solid internal malignancies.

Animals↗

PubMed1998

Effective treatment of cutaneous and subcutaneous malignant tumours by electrochemotherapy.

Electrochemotherapy (ECT) enhances the effectiveness of chemotherapeutic agents by administering the drug in combination with short intense electric pulses. ECT is effective because electric pulses permeabilize tumour cell membranes and allow non-permeant drugs, such as bleomycin, to enter the cells. The aim of this study was to demonstrate the anti-tumour effectiveness of ECT with bleomycin on cutaneous and subcutaneous tumours. This article summarizes results obtained in independent clinical trials performed by five cancer centres. A total of 291 cutaneous or subcutaneous tumours of basal cell carcinoma (32), malignant melanoma (142), adenocarcinoma (30) and head and neck squamous cell carcinoma (87) were treated in 50 patients. Short and intense electric pulses were applied to tumours percutaneously after intravenous or intratumour administration of bleomycin. The tumours were measured and the response to the treatment evaluated 30 days after the treatment. Objective responses were obtained in 233 (85.3%) of the 273 evaluable tumours that were treated with ECT. Clinical complete responses were achieved in 154 (56.4%) tumours, and partial responses were observed in 79 (28.9%) tumours. The application of electric pulses to the patients was safe and well tolerated. An instantaneous contraction of the underlying muscles was noticed. Minimal adverse side-effects were observed. ECT was shown to be an effective local treatment. ECT was effective regardless of the histological type of the tumour. Therefore, ECT offers an approach to the treatment of cutaneous and subcutaneous tumours in patients with minimal adverse side-effects and with a high response rate.

Adenocarcinoma↗

PubMed1998

Antimetastatic effects of electrochemotherapy and of histoincompatible interleukin-2-secreting cells in the murine Lewis lung tumor.

Murine Lewis lung (3LL) tumors are characterized by the appearance of lung metastases after a regular period following their s.c. transplantation. We tested the respective efficiencies of various antitumor treatments: (i) electrochemotherapy (ECT), i.e. the systemic injection of bleomycin associated with electric pulses, locally delivered, that permeabilizes the tumor cells; (ii) intratumoral injection of histoincompatible cells that have been engineered in vitro to secrete high amounts of interleukin-2; and (iii) the combination of these two treatments. The growth of the s.c. transplanted tumors was followed up and the number of lung metastases was counted 14 days after the treatment. ECT alone resulted in the reduction of both the size of the tumor and the number of lung metastases. This latter effect can be partially explained by the effects of ECT on the s.c. tumor mass from which 3LL cells escape to colonize the lungs. The injection of IL-2-secreting cells alone had no effect on the s.c. mass and only a limited effect on the number of lung metastases. However, the combined treatment ECT plus IL-2-secreting cells resulted in antimetastatic effects potentiation that could result from stimulation of a non-specific immune response through an increase of NK activity.

Animals↗

PubMed1998

Effects of detergents on P-glycoprotein atpase activity: differences in perturbations of basal and verapamil-dependent activities.

P-glycoprotein (P-gp), a plasma membrane glycoprotein associated with the multidrug resistance phenotype, is responsible for the ATP-dependent efflux of various amphiphilic drugs. Using membrane vesicles prepared from the multidrug resistant cell line DC-3F/ADX, we studied the perturbation of the basal (i.e. in the absence of drug) and verapamil-dependent P-gp ATPase activities induced by various detergents, at non-solubilizing, as well as at solubilizing, concentrations. The progressive membrane solubilization with increasing detergent concentration was monitored by light scattering and centrifugation experiments. For non-solubilizing detergent concentrations, all tested detergents except DOC induced a partial inhibition of P-gp ATPase activity, which was not correlated with the amount of the various tested detergents incorporated in the membranes. Analysis of the verapamil-induced P-gp activation reveals that P-gp ATPase activity is differently modulated by the various detergents at non-solubilizing concentrations. Thus, specific interactions between P-gp and detergents are more likely to occur rather than a global membrane perturbation. After solubilization by the various tested detergents, the basal P-gp ATPase activity was virtually completely inhibited, except in the presence of CHAPS which was able to preserve this activity at a level comparable to that measured in native membranes. However, the verapamil-induced P-gp ATPase activation was lost during P-gp solubilization by CHAPS, but recovered after dilution of CHAPS below its critical micellar concentration. These observations indicate specific interactions between P-gp and CHAPS molecules within the mixed micelles. On the whole, our data evidencing specific interactions P-gp/detergents are consistent with the location of the drug transport sites on P-gp transmembrane domains.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1997

Competitive and non-competitive inhibition of the multidrug-resistance-associated P-glycoprotein ATPase--further experimental evidence for a multisite model.

P-glycoprotein, a plasma membrane protein overexpressed in multidrug-resistant (MDR) cells, exhibits in vitro an ATPase activity and is responsible for the energy-dependent efflux of structurally unrelated cytotoxic drugs (like vinblastine) and various MDR-reversing agents (like verapamil and progesterone) from these MDR cells. To investigate the mechanism of P-glycoprotein interaction with various compounds, we measured the P-glycoprotein ATPase activity on membrane vesicles prepared from the MDR cell line DC-3F/ADX, and we studied the effects of vinblastine, verapamil and progesterone on this ATPase activity. The basal P-glycoprotein ATPase activity is increased by verapamil and progesterone, with respective half-maximal activating concentrations of approximately 1.5 microM and approximately 25 microM, and activation factors of approximately 1.7 and approximately 2.2. Vinblastine inhibits the activation of P-glycoprotein ATPase induced by verapamil or progesterone with an inhibition constant approximately 0.5 microM in both cases. This demonstrates that vinblastine has a specific modulating site on P-glycoprotein. The combined modulation of P-glycoprotein ATPase by vinblastine and verapamil reveals that these two drugs are mutually exclusive. Since these two molecules have different effects both on the basal P-glycoprotein ATPase activity and on the MgATP concentration dependence of P-glycoprotein ATPase activity, they could bind P-glycoprotein either on different and overlapping sites, or on distant but interacting sites. In contrast, the combined modulation of P-glycoprotein ATPase by vinblastine and progesterone reveals a non-competitive relationship between these two drugs, and hence shows that they can independently and simultaneously bind P-glycoprotein on distinct sites. Since verapamil and progesterone are mutual inhibitors of P-glycoprotein ATPase stimulation in a non-competitive manner, these two molecules can also bind independently P-glycoprotein on separated sites. This is confirmed here by the observation of a synergistic effect when mixtures of verapamil and progesterone are tested for the modulation of P-glycoprotein ATPase. Three MDR-related molecules, taken as models for interaction with P-glycoprotein, appear thus to bind on at least two different separated specific sites. These results favor a multisite model rather than a universal site model to describe the broad substrate specificity characterizing P-glycoprotein function.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1997

First clinical trial of cat soft-tissue sarcomas treatment by electrochemotherapy.

Electrochemotherapy combines bleomycin and local electric pulses that allow cell permeabilization and free access of bleomycin to its intracellular target. We report the first veterinarian clinical trial of electrochemotherapy in 12 cats with spontaneous large soft-tissue sarcomas that suffered relapse after treatment with conventional therapies. Permeabilizing electric pulses were delivered using external surface electrodes, as well as new needle-shaped electrodes that were designed to be inserted in tumours for more effective treatment of several-centimetre-thick tumour nodules. The electric pulses were applied to the tumours several times from 4 to 15-30 min after a bolus intravenous injection of 0.5 mg kg(-1) bleomycin. Tolerance to treatment was excellent without general side-effects. The cats showed local inflammatory reactions for a few days and disease stabilization lasted from 2 weeks to 7 months. One partial regression was observed, and the general absence of nodule volume decrease can be explained by local fibrotic reactions. Histological analysis of biopsies also revealed massive tumour cell death. The cats' lifespan increased (P<<0.001), with a mean survival time of 6.1 months (maximum 18 months) compared with 0.8 months (maximum 1.5 months) for a group of 11 untreated control cats displaying similar carcinological features. Electrochemotherapy is clearly effective as a salvage treatment for large spontaneous solid tumours in adverse clinical situations and this is promising for future applications.

Animals↗

PubMed1996

Effects of steroids and verapamil on P-glycoprotein ATPase activity: progesterone, desoxycorticosterone, corticosterone and verapamil are mutually non-exclusive modulators.

P-glycoprotein (P-gp) is a membranous ATPase responsible for the multidrug resistance (MDR) phenotype. Using membrane vesicles prepared from the highly resistant cell line DC-3F/ADX we studied the influence of P-gp ATPase activity of four progesterone derivatives which specifically bind to P-gp and reverse MDR. Progesterone and desoxycorticosterone stimulate P-gp ATPase activity with, respectively, apparent concentrations giving half-maximal activation of 20-25 microM and 40-50 microM, and activation factors of 2.3 (at 100 microM progesterone) and 1.8 (at 170 microM desoxycorticosterone). Hydrocortisone above 100 microM stimulates P-gp ATPase activity while corticosterone has no apparent stimulating effect. Our data are consistent with the location of the binding sites for the progesterone derivatives on the P-gp membranous domain. The effects of these steroids on verapamil-stimulated P-gp ATPase activity support a non-competitive mechanism, i.e. the binding sites for verapamil and steroids are mutually non-exclusive for P-gp ATPase modulation. A similar non-competitive inhibition of progesterone-stimulated P-gp ATPase activity by desoxycorticosterone or by corticosterone leads to the conclusion that these steroids, although sharing related structures, have distinct modulating sites on P-gp. As expected from their mutually non-exclusive interactions on P-gp, progesterone and verapamil when mixed induce a synergistic modulation of P-gp ATPase activity. Since drug transport by P-gp is believed to be coupled to its ATPase activity, a corresponding synergistic effect of these two modulators for the inhibition of P-gp-mediated drug resistance can be expected.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1996

Antitumor electrochemotherapy: new advances in the clinical protocol.

BACKGROUND: Electrochemotherapy (ECT) is a new antitumor approach that combines systemic bleomycin (BLM) with electric pulses (EP) delivered locally at the tumor site. These EP permeabilize the cells in the tissue, allow BLM delivery inside the cells, and increase BLM cytotoxicity. As an extension of our initial Phase I trial on patients with head and neck squamous cell carcinoma (HNSCC) permeation nodules, we tested variations of ECT protocol to determine how to improve it. METHODS: Seven patients with multiple and/or large permeation nodules of HNSCC or of salivary or breast adenocarcinoma were treated in 10 sessions. They received BLM followed by runs of four or eight short (100 microseconds) and intense (1000 or 1300 V/cm-1) EP delivered at adjacent positions on the nodules to cover all of the tumor surface. RESULTS: We determined the therapeutic window for EP delivery to be between 8 and 28 minutes after BLM intravenous injection. We showed patient tolerance to a high number of EP, along with ECT feasibility after BLM intraarterial injection or on adenocarcinoma nodules. Clear antitumor effects were obtained, especially in the small nodules. In the largest nodules we observed extended tumor necrosis. CONCLUSIONS: Relatively efficient ECT can be performed for large and think nodules, and ECT remains safe even when a large number of EP are delivered. However, in this study, ECT's effectiveness on large nodules was lower than on the previously treated small nodules, probably due to external electrodes inadequacy. The data reported stimulated us to design a new device for EP delivery.

Adult↗

PubMed1996

Bleomycin: revival of an old drug.

1. Bleomycin (BLM) is a cytotoxic drug currently used in anticancer chemotherapy. We present here a summary of the well established "old" knowledge concerning BLM structure, properties and activity at the molecular level, as well as its current clinical uses. 2. Then, we introduce "new" recent facts concerning BLM interaction with animal cells, that demonstrate the peculiar characteristics of that drug and its potentialities. Indeed, BLM has an high intrinsic cytotoxicity (i.e. it is a very potent drug once inside the cell). However, BLM cytotoxicity is limited because BLM is unable to diffuse through the plasma membrane. The very low amounts of BLM that can reach the cell interior enter the cells by a mechanism that requires BLM interaction with a plasma membrane protein. 3. Finally, we present and discuss a new possible use of BLM in an antitumor approach that we term electrochemotherapy. This new treatment, still under development, is based on the increased BLM delivery into tumor cells after cell permeabilization by electric pulses administered locally at the solid tumor site. This results in a huge local potentiation of BLM activity, in the absence of systemic adverse effects. Clinical trials are in progress.

Animals↗

PubMed1996

Pennsylvania physicians can now share the risk.

Good news for Pennsylvania physicians: Early last month, the state announced major changes in policy toward integrated delivery systems (IDSs). This article summarizes the major regulatory changes which physicians considering involvement in any type of IDS need to know.

Humans↗

PubMed1995

Systemic antitumor effects of electrochemotherapy combined with histoincompatible cells secreting interleukin-2.

Electrochemotherapy is an antitumor treatment that combines a cytotoxic drug with the local administration of electric pulses delivered at the tumor site. We previously found that in mice the cure rate of subcutaneous transplanted tumors treated by electrochemotherapy is increased by repeated systemic interleukin-2 (IL-2) injections. Moreover, histoincompatible cells engineered to secrete IL-2 allow the rejection of syngeneic tumor cells when both cells are inoculated together. In this study of preestablished tumors in mice we show that after electrochemotherapy, delayed peritumoral injections of histoincompatible IL-2-producing cells result in the cure of almost all the tumors. Moreover, this combined local treatment leads to cures of untreated, contralaterally transplanted tumors. This systemic antitumor immunity also resulted in complete protection of the cured mice against further inocula of the tumor cells. These results, which were obtained using allogeneic as well as xenogeneic IL-2-secreting cells, suggest that electrochemotherapy combined with such cellular immunotherapy might be a useful approach for the treatment of metastasizing cancers.

Animals↗

PubMed1994

Involvement of membrane bleomycin-binding sites in bleomycin cytotoxicity.

The authors have recently shown the existence of bleomycin (BLM)-binding sites at the surface of DC-3F cells. In order to study the involvement of these sites in the sensitivity of the cells to bleomycin several BLM-resistant cell lines from DC-3F cells were analysed. These mutants were obtained by electrotransfection of the Sh ble gene (D/BlmI cells) or the Sh ble-beta Gal fusion gene (D/BlmII cells) and/or by continuous culture in the presence of BLM (D/BlmIR and D/Blm40 cells). The resistance levels of the D/BlmII and D/Blm40 cells were 50- and 22-fold, respectively, determined at the EC50 level. The D/BlmI cells were only 2-fold resistant, whereas D/BlmIR cells were so resistant that almost no cytotoxicity was detected up to 200 microM BLM external concentration. Electropermeabilization was used in an attempt to bypass the plasma membrane of the cells and permit the distinction between internal resistance and membrane resistance. The former was observed when the products of the transfected genes were present. With respect to membrane resistance, differences were detected in the number of BLM-binding sites in several mutant cell lines, which could account for the differences in cell sensitivity to BLM. This suggests that the BLM-binding sites found at the cell surface may play a crucial role in BLM internalization and consequently in its cytotoxicity.

Animals↗

PubMed1994

Electropermeabilization of cells in tissues assessed by the qualitative and quantitative electroloading of bleomycin.

Using cells in suspension, electropermeabilization is a technique extensively used to transfect living cells or to introduce a variety of compounds inside the cells. Here we demonstrate the reality of the tissue electropermeabilization using qualitative and quantitative determinations of the electroloading of bleomycin considered as an nonpermeant molecule that serves as an indicator of the permeabilization. In tissues, cell electropermeabilization is achieved for electric field intensities lower than those necessary to permeabilize the same cells in suspension. We also emphasize the importance of the geometry of the electric field lines defined by the electrodes for permeabilizing a whole tissue, for example a tumor.

Animals↗

PubMed1993

Electrochemotherapy, a new antitumor treatment. First clinical phase I-II trial.

BACKGROUND: Electrochemotherapy is a new antitumor treatment consisting of electrical pulses administered to the tumor several minutes after intravenous injection of bleomycin. In mice, important antitumor effects were observed on subcutaneously transplanted tumors and on spontaneously occurring mammary carcinomas. Cures were obtained after one single treatment combining bleomycin and electric pulses. In humans, permeation nodules seemed an adequate oncologic situation to assay this new procedure. The authors report the first Phase I-II trial of electrochemotherapy. METHODS: Eight patients with 40 permeation nodules of head and neck squamous cell carcinomas were treated with 10 mg/m2 bleomycin intravenous bolus, followed by four or eight short (100 microseconds) and intense (1300 V/cm) pulses administered through two external electrodes located on each side of the treated nodule. RESULTS: An instantaneous painless contraction of the underlying muscles was regularly observed. Neither local nor general side effects were observed, and electrochemotherapy was well tolerated. In addition, a clear local antitumor efficacy was found: 23 (57%) nodules were in clinical complete response within a few days. CONCLUSION: The absence of toxicity, the good tolerance by the patients, and the net antitumor effects observed are encouraging for additional electrochemotherapy developments in clinical oncology.

Adult↗