Electrochemotherapy of tumours resistant to cisplatin: a study in a murine tumour model

Threshold Interphase Delay for Bipolar Pulses to Prevent Cancellation Phenomenon during Electrochemotherapy

Electroporation-based procedures employing nanosecond bipolar pulses are commonly linked to an undesirable phenomenon known as the cancelation effect. The cancellation effect arises when the second pulse partially or completely neutralizes the effects of the first pulse, simultaneously diminishing cells' plasma membrane permeabilization and the overall efficiency of the procedure. Introducing a temporal gap between the positive and negative phases of the bipolar pulses during electroporation procedures may help to overcome the cancellation phenomenon; however, the exact thresholds are not yet known. Therefore, in this work, we have tested the influence of different interphase delay values (from 0 ms to 95 ms) using symmetric bipolar nanoseconds (300 and 500 ns) on cell permeabilization using 10 Hz, 100 Hz, and 1 kHz protocols. As a model mouse hepatoma, the MH-22a cell line was employed. Additionally, we conducted in vitro electrochemotherapy with cisplatin, employing reduced interphase delay values (0 ms and 0.1 ms) at 10 Hz. Cell plasma membrane permeabilization and viability dependence on a variety of bipolar pulsed electric field protocols were characterized. It was shown that it is possible to minimize bipolar cancellation, enabling treatment efficiency comparable to monophasic pulses with identical parameters. At the same time, it was highlighted that bipolar cancellation has a significant influence on permeabilization, while the effects on the outcome of electrochemotherapy are minimal.

Electrochemotherapy for head and neck cancers: possibilities and limitations

Head and neck cancer continues to be among the most prevalent types of cancer globally, yet it can be managed with appropriate treatment approaches. Presently, chemotherapy and radiotherapy stand as the primary treatment modalities for various groups and regions affected by head and neck cancer. Nonetheless, these treatments are linked to adverse side effects in patients. Moreover, due to tumor resistance to multiple drugs (both intrinsic and extrinsic) and radiotherapy, along with numerous other factors, recurrences or metastases often occur. Electrochemotherapy (ECT) emerges as a clinically proven alternative that offers high efficacy, localized effect, and diminished negative factors. Electrochemotherapy involves the treatment of solid tumors by combining a non-permeable cytotoxic drug, such as bleomycin, with a locally administered pulsed electric field (PEF). It is crucial to employ this method effectively by utilizing optimal PEF protocols and drugs at concentrations that do not possess inherent cytotoxic properties. This review emphasizes an examination of diverse clinical practices of ECT concerning head and neck cancer. It specifically delves into the treatment procedure, the choice of anti-cancer drugs, pre-treatment planning, PEF protocols, and electroporation electrodes as well as the efficacy of tumor response to the treatment and encountered obstacles. We have also highlighted the significance of assessing the spatial electric field distribution in both tumor and adjacent tissues prior to treatment as it plays a pivotal role in determining treatment success. Finally, we compare the ECT methodology to conventional treatments to highlight the potential for improvement and to facilitate popularization of the technique in the area of head and neck cancers where it is not widespread yet while it is not the case with other cancer types.

Micro- and Nanosecond Pulses Used in Doxorubicin Electrochemotherapy in Human Breast and Colon Cancer Cells with Drug Resistance

(1) Background: Pulsed electric field (PEF) techniques are commonly used to support the delivery of various molecules. A PEF seems a promising method for low permeability drugs or when cells demonstrate therapy resistance and the cell membrane becomes an impermeable barrier. (2) Methods: In this study, we have used doxorubicin-resistant and sensitive models of human breast cancer (MCF-7/DX, MCF-7/WT) and colon cancer cells (LoVo, LoVoDX). The study aimed to investigate the susceptibility of the cells to doxorubicin (DOX) and electric fields in the 20–900 ns pulse duration range. The viability assay was utilized to evaluate the PEF protocols’ efficacy. Cell confluency and reduced glutathione were measured after PEF protocols. (3) Results: The obtained results showed that PEFs significantly supported doxorubicin delivery and cytotoxicity after 48 and 72 h. The 60 kV/cm ultrashort pulses × 20 ns × 400 had the most significant cytotoxic anticancer effect. The increase in DOX concentration provokes a decrease in cell viability, affected cell confluency, and reduced GSSH when combined with the ESOPE (European Standard Operating Procedures of Electrochemotherapy) protocol. Additionally, reactive oxygen species after PEF and PEF-DOX were detected. (4) Conclusions: Ultrashort electric pulses with low DOX content or ESOPE with higher DOX content seem the most promising in colon and breast cancer treatment.

The Impact of Extracellular Ca2+ and Nanosecond Electric Pulses on Sensitive and Drug-Resistant Human Breast and Colon Cancer Cells

Simple Summary

The drug resistance phenomenon in cancer constantly induces problems in therapeutic protocols. Pulsed electric fields (PEFs) seem to be a promising method in drug molecule delivery. Here we have proved that electroporation supported by calcium ions can alternate the activity of drug resistance proteins. Our results indicated that MDR1 expression is not significantly modified by nanosecond electroporation in multidrug-resistant cells. However, PEF significantly inhibited MDR1 activity and cell viability when combined with calcium ions.

Abstract

(1) Background: Calcium electroporation (CaEP) is based on the application of electrical pulses to permeabilize cells (electroporation) and allow cytotoxic doses of calcium to enter the cell. (2) Methods: In this work, we have used doxorubicin-resistant (DX) and non-resistant models of human breast cancer (MCF-7/DX, MCF-7/WT) and colon cancer cells (LoVo, LoVo/DX), and investigated the susceptibility of the cells to extracellular Ca²⁺ and electric fields in the 20 ns–900 ns pulse duration range. (3) Results: We have observed that colon cancer cells were less susceptible to PEF than breast cancer cells. An extracellular Ca²⁺ (2 mM) with PEF was more disruptive for DX-resistant cells. The expression of glycoprotein P (MDR1, P-gp) as a drug resistance marker was detected by the immunofluorescent (CLSM) method and rhodamine-123 efflux as an MDR1 activity. MDR1 expression was not significantly modified by nanosecond electroporation in multidrug-resistant cells, but a combination with calcium ions significantly inhibited MDR1 activity and cell viability. (4) Conclusions: We believe that PEF with calcium ions can reduce drug resistance by inhibiting drug efflux activity. This phenomenon of MDR mechanism disruption seems promising in anticancer protocols.

Biological factors of the tumour response to electrochemotherapy: Review of the evidence and a research roadmap

The beneficial effects of electrochemotherapy (ECT) for superficial tumours and, more recently, deep-seated malignancies in terms of local control and quality of life are widely accepted. However, the variability in responses across histotypes needs to be explored. Currently, patient selection for ECT is based on clinical factors (tumour size, histotype, and exposure to previous oncological treatments), whereas there are no biomarkers to predict the response to treatment. In this field, two major areas of investigation can be identified, i.e., tumour cell characteristics and the tumour microenvironment (vasculature, extracellular matrix, and immune infiltrate). For each of these areas, we describe the current knowledge and discuss how to foster further investigation. This review aims to provide a summary of the currently used guiding clinical factors and delineates a research roadmap for future studies to identify putative biomarkers of response to ECT. These biomarkers may allow researchers to improve ECT practice by customising treatment parameters, manipulating the tumour and its microenvironment, and exploring novel therapeutic combinations.

Electropermeabilization of metastatic chondrosarcoma cells from primary cell culture

Primary cell cultures are challenging, but reliable model reflecting tumor response in vitro. The study was designed to examine if the increased electropermeabilization can overcame initial drug insensitivity in chondrosarcoma cells from lung metastasis. We established a primary cell culture and evaluated the cytotoxic impact of four drugs-cisplatin (CDDP), camptothecin, 2-methoxyestradiol, and leucovorin calcium (LeuCa). After determination of parameters allowing for electropermeabilization, we performed electrochemotherapy in vitro with the least toxic drugs-CDDP and LeuCa. Although combining CDDP and leucovorin together increased their toxicity and supported apoptosis, application of pulsed electric fields (PEFs) brought no advantage for their efficacy. The study emphasizes the need for introduction of primary cell cultures into studies on pulse electric fields as model frequently less sensitive to PEF-based treatments than continuous cell lines.

A Novel Method for Controlled Gene Expression via Combined Bleomycin and Plasmid DNA Electrotransfer

Electrochemotherapy is an efficient method for the local treatment of cutaneous and subcutaneous metastases, but its efficacy as a systemic treatment remains low. The application of gene electrotransfer (GET) to transfer DNA coding for immune system modulating molecules could allow for a systemic effect, but its applications are limited because of possible side effects, e.g., immune system overactivation and autoimmune response. In this paper, we present the simultaneous electrotransfer of bleomycin and plasmid DNA as a method to increase the systemic effect of bleomycin-based electrochemotherapy. With appropriately selected concentrations of bleomycin and plasmid DNA, it is possible to achieve efficient cell transfection while killing cells via the cytotoxic effect of bleomycin at later time points. We also show the dynamics of both cell electrotransfection and cell death after the simultaneous electrotransfer of bleomycin and plasmid DNA. Therefore, this method could have applications in achieving the transient, cell death-controlled expression of immune system activating genes while retaining efficient bleomycin mediated cell killing.

Connecting the in vitro and in vivo experiments in electrochemotherapy - a feasibility study modeling cisplatin transport in mouse melanoma using the dual-porosity model

In electrochemotherapy two conditions have to be met to be successful - the electric field of sufficient amplitude and sufficient uptake of chemotherapeutics in the tumor. Current treatment plans only take into account critical electric field to achieve cell membrane permeabilization. However, permeabilization alone does not guarantee uptake of chemotherapeutics and consequently successful treatment. We performed a feasibility study to determine whether the transport of cisplatin in vivo could be calculated based on experiments performed in vitro. In vitro, a spectrum of parameters can be explored without ethical issues. Mouse melanoma B16-F1 cell suspension and inoculated B16-F10 tumors were exposed to electric pulses in the presence of chemotherapeutic cisplatin. The uptake of cisplatin was measured by inductively coupled plasma mass spectrometry. We modeled the transport of cisplatin with the dual-porosity model, which is based on the diffusion equation, connects pore formation with membrane permeability, and includes transport between several compartments. In our case, there were three compartments - tumor cells, interstitial fraction and peritumoral region. Our hypothesis was that in vitro permeability coefficient could be introduced in vivo, as long as tumor physiology was taken into account. Our hypothesis was confirmed as the connection of in vitro and in vivo experiments was possible by introducing a transformation coefficient which took into account the in vivo characteristics, i.e., smaller available area of the plasma membrane for transport due to cell density, presence of cell-matrix in vivo, and reduced drug mobility. We thus show that it is possible to connect in vitro and in vivo experiments of electrochemotherapy. However, more experimental work is required for model validation.

Electroporation with Cisplatin against Metastatic Pancreatic Cancer: In Vitro Study on Human Primary Cell Culture

Despite the rapid progression of cancer pharmacotherapy, the high drug resistance of pancreatic ductal adenocarcinoma (PDA) makes it one of the most lethal malignancies. Therefore, there are high expectations associated with experimental therapies, such as electrochemotherapy (ECT). This technique involves the application of short electric pulses to induce transitional permeabilization of the cellular membrane, thus enhancing drug molecules influx. The aim of the study was to investigate the influence of electroporation with cisplatin (CisEP) on the primary culture of human PDA cells from lung metastases-their survival and stress response. Considering the growing importance of various research models, two established human PDA cell lines, EPP85-181P (sensitive to daunorubicin) and EPP85-181RDB (resistant to daunorubicin), were utilized as a reference control. Cisplatin revealed higher cytotoxicity towards established cell lines. Following CisEP application, we observed a significant decrease of cells viability in the primary culture model. After CisEP therapy, an increased immunoreactivity with SOD-2 and Casp-3 antibodies was noticed. In conclusion, we discovered that electroporation can enhance the cytotoxic effect of cisplatin in pancreatic cancer cells in vitro. This effect was evident for cells from the primary culture. The obtained results confirm the importance of primary cells models in studies on the efficacy of experimental cancer therapies.

In Vitro and in vivo Evaluation of Electrochemotherapy with trans-platinum Analogue trans-[PtCl2(3-Hmpy)2]

Background

Cisplatin is used in cancer therapy, but its side effects and acquired resistance to cisplatin have led to the synthesis and evaluation of new platinum compounds. Recently, the synthesized platinum compound trans-[PtCl₂(3-Hmpy)₂] (3-Hmpy = 3-hydroxymethylpyridine) (compound 2) showed a considerable cytotoxic and antitumour effectiveness. To improve compound 2 cytotoxicity in vitro and antitumour effectiveness in vivo, electroporation was used as drug delivery approach to increase membrane permeability (electrochemotherapy).

Materials and methods

In vitro, survival of sarcoma cells with different intrinsic sensitivity to cisplatin (TBLCl2 sensitive, TBLCl2Pt resistant and SA-1 moderately sensitive) was determined using a clonogenic assay after treatment with compound 2 or cisplatin electrochemotherapy. In vivo, the antitumour effectiveness of electrochemotherapy with compound 2 or cisplatin was evaluated using a tumour growth delay assay. In addition, platinum in the serum, tumours and platinum bound to the DNA in the cells were performed using inductively coupled plasma mass spectrometry.

Results

In vitro, cell survival after treatment with compound 2 electrochemotherapy was significantly decreased in all tested sarcoma cells with different intrinsic sensitivity to cisplatin (TBLCl2 sensitive, TBLCl2Pt resistant and SA-1 moderately sensitive). However, this effect was less pronounced compared to cisplatin. Interestingly, the enhancement factor (5-fold) of compound 2 cytotoxicity was equal in cisplatin-sensitive TBLCl2 and cisplatin-resistant TBLCl2Pt cells. In vivo, the growth delay of subcutaneous tumours after treatment with compound 2 electrochemotherapy was lower compared to cisplatin. The highest antitumour effectiveness after cisplatin or compound 2 electrochemotherapy was obtained in TBLCl2 tumours, resulting in 67% and 11% of tumour cures, respectively. Compound 2 induced significantly smaller loss of animal body weight compared to cisplatin. Furthermore, platinum amounts in tumours after compound 2 or cisplatin electrochemotherapy were approximately 2-fold higher compared to the drug treatment only, and the same increase of platinum bound to DNA was observed.

Conclusions

The obtained results in vitro and in vivo suggest compound 2 as a potential antitumour agent in electrochemotherapy.

Enhanced Anti-tumour Effect of Cisplatin with Low-voltage Electrochemotherapy in Hamster Oral Fibrosarcoma

The aim of this study was to determine the effects of low-voltage electrochemotherapy with intraperitoneal cisplatin on hamster oral fibrosarcoma. Oral fibrosarcoma was transplanted sub-mucosally into the cheek pouch mucosa of 100 hamsters. After transplantation, the hamsters were randomly divided into four equal groups. These groups received no treatment (D-E-); 2 mg/kg body weight cisplatin treatment without electroporation (D+E-); electroporation without cisplatin treatment (D-E+);or 2 mg/kg body weight cisplatin treatment followed by electroporation (D+E+). Electrical pulse treatment together with cisplatin injection markedly reduced the size of the tumour, whereas cisplatin injection or electrical pulse treatment alone did not. These results clearly indicate that the anti-tumour effect of cisplatin on hamster oral fibrosarcoma was considerably potentiated or enhanced by the administration of local electrical pulses at low voltages.

Locally enhanced chemotherapy by electroporation: clinical experiences and perspective of use of electrochemotherapy

Electroporation is used to enhance drug diffusion and gene delivery into the cytosol. The combination of electroporation and cytotoxic drugs, electrochemotherapy (ECT), is used to treat metastatic tumor nodules located at the skin and subcutaneous tissue. The objective response rate following a single session of treatment exceeds 80%, with minimal toxicity for the patients. The efficacy of ECT in the bone and visceral metastasis is currently investigated, and Phase II studies have been completed. ECT has been used to treat skin primary tumors, except melanoma, and is under investigation for locally advanced pancreatic cancer. Early evidence suggests that treatment of tumor nodules with ECT recruits components of the immune system and eliciting a systemic immune response against cancer is a challenging clinical perspective. Considering the proven safety in several different clinical applications electroporation should be viewed as a clinical platform technology with wide perspectives for use in ECT, gene therapy and DNA vaccination.

Electrochemotherapy: from the drawing board into medical practice

Electrochemotherapy is a local treatment of cancer employing electric pulses to improve transmembrane transfer of cytotoxic drugs. In this paper we discuss electrochemotherapy from the perspective of biomedical engineering and review the steps needed to move such a treatment from initial prototypes into clinical practice. In the paper also basic theory of electrochemotherapy and preclinical studies in vitro and in vivo are briefly reviewed. Following this we present a short review of recent clinical publications and discuss implementation of electrochemotherapy into standard of care for treatment of skin tumors, and use of electrochemotherapy for other targets such as head and neck cancer, deep-seated tumors in the liver and intestinal tract, and brain metastases. Electrodes used in these specific cases are presented with their typical voltage amplitudes used in electrochemotherapy. Finally, key points on what should be investigated in the future are presented and discussed.

In vivo MRI Follow-up of Murine Tumors Treated by Electrochemotherapy and other Electroporation-based Treatments

In vivo cell electropermeabilization can be used alone or in combination with a hydrophilic, nonpermeant cytotoxic drug such as bleomycin (electrochemotherapy) to efficiently treat tumors. We used magnetic resonance imaging to detect rapid structural modifications in tumors treated by electroporation-based methods. Water diffusion coefficient (ADC), transverse relaxation time (T2) and tumor volume of fibrosarcomas xenografted on syngenic mice were measured upon 3 groups of 6 treated mice within the 48 hrs following ECT done with a normal (BE) or a high dose of bleomycin (HBE), and after irreversible electroporation (IRE), and in three control groups. As expected, the tumor volume increased in the control groups at 48 hrs (p < 0.05) and the values of ADC and T2 did not varied significantly in the control groups except for ADC decrease and T2 increase observed between 3 hrs and 24 hrs (p < 0.03) in the group that received bleomycin only. Tumor volumes decreased significantly at 24 hrs in the IRE and HBE groups. The mean tumor ADC increased significantly at 24 hrs (+17.6%, p < 0.03) in the BE group, probably reflecting apoptosis, while in the HBE group the mean tumor ADC increased earlier, at 10 hrs (+19%, p < 0.03) because of the speed of the pseudoapopototic process. In the IRE group, the mean tumor ADC decreased significantly at 1 hrs (p < 0.05) and 3 hrs (p < 0.03), and T2 decreased (p < 0.03), both probably reflecting cell swelling induced by the vascular lock. Thus ADC and T2 changes in the treated tumors correlated with previous histological observations on the same tumor models. Noteworthy, ADC allowed the visualization of early and rapid changes in the treated tumors, when tumor volume monitoring was not yet able to detect any effect of the treatments.

Potentiation of electrochemotherapy by intramuscular IL-12 gene electrotransfer in murine sarcoma and carcinoma with different immunogenicity

Background.

Electrochemotherapy provides good local tumor control but requires adjuvant treatment for increased local response and action on distant metastasis. In relation to this, intramuscular interleukin-12 (IL-12) gene electro-transfer, which provides systemic shedding of IL-12, was combined with local electrochemotherapy with cisplatin. Furthermore, the dependence on tumor immunogenicity and immunocompetence of the host on combined treatment response was evaluated.

Materials and methods.

Sensitivity of SA-1 sarcoma and TS/A carcinoma cells to electrochemotherapy with cisplatin was tested in vitro. In vivo, intratumoral electrochemotherapy with cisplatin (day 1) was combined with a single (day 0) or multiple (days 0, 2, 4) intramuscular murine IL-12 (mIL-12) gene electrotransfer. The antitumor effectiveness of combined treatment was evaluated on immunogenic murine SA-1 sarcoma in A/J mice and moderately immunogenic murine TS/A carcinoma, in immunocompetent BALB/c and immunodeficient SCID mice.

Results.

Electrochemotherapy in vitro resulted in a similar IC₅₀ values for both sarcoma and carcinoma cell lines. However, in vivo electrochemotherapy was more effective in the treatment of sarcoma, the more immunogenic of the tumors, resulting in a higher log cell kill, longer specific tumor growth delay, and also 17% tumor cures compared to carcinoma where no tumor cures were observed. Adjuvant intramuscular mIL-12 gene electrotransfer increased the log cell kill in both tumor models, potentiating the specific tumor growth delay by a factor of 1.8-2 and increasing tumor cure rate by approximately 20%. In sarcoma tumors, the potentiation of the response by intramuscular mIL-12 gene electrotransfer was dose-dependent and also resulted in a faster onset of tumor cures. Comparison of the carcinoma response to the combined treatment modality in immunocompetent and immunodeficient mice demonstrated that the immune system is needed both for increased cell kill and for attaining tumor cures.

Conclusions.

Based on the comparison of the antitumor effectiveness of electrochemotherapy to intratumoral cisplatin administration, we can conclude that the fraction of cells killed and the tumor cure rate are higher in immunogenic sarcoma tumor compared to moderately immunogenic carcinoma tumor. The tumor cell kill and cure rate depend on the immune response elicited by the destroyed tumor cells, which might depend on the tumor immunogenicity. The effect of adjuvant intramuscular mIL-12 gene electrotransfer is dependent on the amount of IL-12 in the system and the immune competence of the host, as demonstrated by the dose-dependent increase in the cure rate of SA-1 tumors after multiple intramuscular mIL-12 gene electrotransfer and in the differential cure rate of TS/A tumors growing in immunocompetent and immunodeficient mice.

A system for the determination of planar lipid bilayer breakdown voltage and its applications

In this paper, we focus on measurement principles used in electroporation studies on planar lipid bilayers. In particular, we point out the voltage-clamp measurement principle that has great importance when the breakdown voltage of a planar lipid bilayer is under consideration; however, it is also appropriate for the determination of other planar lipid bilayer electrical properties such as resistance and capacitance. A new experimental system that is based on the voltage-clamp measurement principle is described. With the use of a generator that can generate arbitrary-type signals, many specific shapes of a voltage signal could be generated, and therefore, the experimental system is appropriate for a broad spectrum of measurements.

Low-intensity ultrasound and microbubbles enhance the antitumor effect of cisplatin

Cell permeabilization using microbubbles (MB) and low-intensity ultrasound (US) have the potential for delivering molecules into the cytoplasm. The collapsing MB and cavitation bubbles created by this collapse generate impulsive pressures that cause transient membrane permeability, allowing exogenous molecules to enter the cells. To evaluate this methodology in vitro and in vivo, we investigated the effects of low-intensity 1-MHz pulsed US and MB combined with cis-diamminedichloroplatinum (II) (CDDP) on two cell lines (Colon 26 murine colon carcinoma and EMT6 murine mammary carcinoma) in vitro and in vivo on severe combined immunodeficient mice inoculated with HT29-luc human colon carcinoma. To investigate in vitro the efficiency of molecular delivery by the US and MB method, calcein molecules with a molecular weight in the same range as that of CDDP were used as fluorescent markers. Fluorescence measurement revealed that approximately 10(6)-10(7) calcein molecules per cell were internalized. US-MB-mediated delivery of CDDP in Colon 26 and EMT6 cells increased cytotoxicity in a dose-dependent manner and induced apoptosis (nuclear condensation and fragmentation, and increase in caspase-3 activity). In vivo experiments with xenografts (HT29-luc) revealed a very significant reduction in tumor volume in mice treated with CDDP + US + MB compared with those in the US + CDDP groups for two different concentrations of CDDP. This finding suggests that the US-MB method combined with chemotherapy has clinical potential in cancer therapy.

99mTc-DTPA Uptake and Electrical Impedance Measurements in Verification ofIn VivoElectropermeabilization Efficiency in Rat Muscle

OBJECTIVE

In vivo electropermeabilization of cell membranes in rat muscle tissue cause a significant decrease of the electrical impedance, in the frequency region of 1-10 kHz. We aimed to study how the 99mTc-DTPA uptake in the electropermeabilized region correlates to the change of admittance Y = 1/absZ, where Z is the measured impedance.

METHODS

The electropermeabilization was performed in vivo by applying high-voltage (0.5-2 kV) short (0.1-2 ms) pulses through gold-plated needle electrodes in skeletal muscle. The impedance was measured before and after each electropermeabilization pulse. The uptake of 99mTc-DTPA uptake in the electropermeabilized region was measured after 6 and 24 hours with a gamma camera.

RESULTS

The pulse shape (square and exponential), duration, and amplitude of the applied electric field were varied, and electropermeabilization efficiency was evaluated using the various measurement modalities. Good correlations were found (correlation coefficient approximately 0.9) between the 99mTc-DTPA uptake in the electropermeabilized and control "region of interest" the admittance ratio Y (post-treatment)/Y (pretreatment), and charge displacement parameter Q.

CONCLUSION

The electrical impedance measurements method can be utilized in clinical settings to verify the efficiency of electropermeabilization applied to chemotherapy and to power RNAi (RNA-interference) and DNA-plasmid transfection in vaccination, immunization, and gene-therapy.

Electrochemotherapy a novel approach to the treatment of metastatic nodules on the skin and subcutaneous tissues

Electrochemotherapy (ECT) is a new treatment for metastatic nodules of solid tumors on the skin or subcutaneous tissue. ECT is a combination of a physical effect, cell membrane poration, and cytotoxic drug administration. Cell membrane poration is achieved by applying short intense electric filed pulses. Pore formation on the cell membrane allows low permeant drugs like bleomycin or cisplatin to enter the cell and thus locally increase their toxicity: up to 10.000 times for bleomycin and 80 times for cisplatin. ECT has been investigated in a multicenter study European Standard Operating Procedures for Electrochemotherapy (ESOPE) that demonstrates how by ECT over 80% of the cutaneous or subcutaneous metastatic nodules can be healed, thus confirming the results of previous studies. ECT efficacy is independent of tumor histology. The experience gathered in the ESOPE study allowed to prepare standard operating procedures that are key to the dissemination of the technology. ECT is safe effective, the treatment is completed in one session usually on an out-patient basis with minimum side-effects. ECT is cost-effective and, although palliative, it ameliorates patients' quality of life. ECT is the treatment of choice for tumors refractory to conventional treatment, can be used in form of cytoreductive therapy before conventional treatment for organ sparing and functions saving, finally can be adopted to treat hemorrhagic or painful nodules, it can be applied in previously irradiated areas.

Electroporation of transplantable tumour for the enhanced accumulation of photosensitizers

The aim of this study was to verify whether electroporation could increase the accumulation of the hydrophilic photosensitizers: aluminium phthalocyanine tetrasulphonate (AlPcS(4)) and chlorin e(6) (C e(6)) in tumour tissue. The experiment was performed in vivo using hybrid mice (C57Bl/CBA) bearing hepatoma A22 (MH-A22) tumours transplanted in the right haunch. The time dependence of the fluorescence intensity of administered photosensitizers was measured after the ordinary and electrically stimulated delivery. The obtained fluorescence spectroscopy results implied the tumour being affected by an electrical field in a way, which led to a higher accumulation of both photosensitizers (AlPcS(4) and C e(6)) in the periphery of the tumour and it superficial layer. Our pilot study suggests that electroporation could be considered as a useful procedure seeking for the more effective application of photodynamic tumour treatment.

Uptake of antitumor platinum(II)-complexes by cancer cells, assayed by inductively coupled plasma mass spectrometry (ICP-MS)

A systematic study on intracellular Pt uptake and Pt accumulation ratio in breast cancer MCF-7 cell line has been performed on a number of Pt(II)-complexes, namely cisplatin, carboplatin and oxaliplatin, clinically employed as antitumor drugs, trans- and cis-[Pt(Cl)2(pyridine)2] and cis-[Pt(Cl)2(pyridine)(5-SO3H-isoquinoline)] complexes, previously investigated also as potential telomerase inhibitors. In particular, long incubation times have been chosen in order to understand the fate of the complexes in the cells. For this purpose, sub-acute drug concentrations must be employed and, therefore, a very sensitive method of analysis like as inductively coupled plasma mass spectrometry (ICP-MS) superior to the widely employed atomic absorption spectroscopy (AAS) has been adopted. Any relationships among uptake/accumulation and several parameters such as drug structure, lipophilicity, drug concentration and incubation time have been sought and analyzed: the bulk of data point for a passive diffusion mechanism through the cell membrane.

Digression on membrane electroporation for drug and gene delivery

Membrane electroporation (ME) defines an electrical technique to render lipid membranes porous and permeable, transiently and reversibly, by external voltage pulses. Although there are numerous applications of ME to manipulate cells, organelles and tissues in cell biology, biotechnology and medicine, yet the molecular mechanism of ME is only slowly being understood. A general chemical- thermodynamical approach for the quantitative description of cell membrane electroporation has been developed to provide the framework to quantitatively rationalize electroporative cell transformation and electroporative uptake of drug-like dyes into cells, as well as electrolyte efflux from salt-filled electroporated vesicles. Mechanistically, the electroporative transfer of gene and drug-like dyes involves the coupling between an interactive contact formation of the permeates with the cell surface membrane and the structural electroporation-resealing cycle C <--> (P) where C is the closed and (P) represents a number of different porated membrane states, respectively. The experimentally accessible concentration fraction f(p) = [(P)] / ([C] + [(P)]) of porous states is related to thermodynamic and electro-mechanic parameters such as temperature and the electric field strength, membrane rigidity or curvature. The results of the theoretical approach, mainly based on electrooptical data of lipid vesicles, have been successfully used to analyze single cells and to specify conditions for the practical purpose of direct electroporative gene transfer and drug delivery, in particular in the new medical disciplines of electroporative chemotherapy and electroporative gene vaccination.

Enhancing the effectiveness of drug-based cancer therapy by electroporation (electropermeabilization)

Many conventional chemotherapeutic drugs, as well as DNA for cancer gene therapy, require efficient access to the cell interior to be effective. The cell membrane is a formidable barrier to many of these drugs, including therapeutic DNA constructs. Electropermeabilization (EP, often used synonymously with "electroporation") has become a useful method to temporarily increase the permeability of the cell membrane, allowing a broad variety of molecules efficient access to the cell interior. EP is achieved by the application of short electrical pulses of relatively high local field strength to the target tissue of choice. In cancer therapy, EP can be applied in vivo directly to the tumor to be treated, in order to enhance intracellular uptake of drugs or DNA. Alternatively, EP can be used to deliver DNA into cells of healthy tissue to achieve longer-lasting expression of cancer-suppressing genes. In addition, EP has been used in ex vivo therapeutic approaches for the transfection of a variety of cells in suspension. In this paper, we communicate results related to the development of a treatment for squamous cell carcinomas of the head and neck, using electropermeabilization to deliver the drug bleomycin in vivo directly into the tumor cells. This drug, which is not particularly effective as a conventional therapeutic, becomes highly potent when the intracellular concentration is enhanced by EP treatment. In animal model experiments we found a drug dose of 1 U/cm(3) tumor tissue (delivered in 0.25 mL of an aqueous solution/cm3 tumor tissue) and an electrical field strength of 750 V/cm or higher to be optimal for the treatment of human squamous cell tumors grown subcutaneously in mice. Within 24-48 hours, the majority of tumor cells are rapidly destroyed by this bleomycin-electroporation therapy (B-EPT). This raises the concern that healthy tissue may be similarly affected. In studies with large animals we showed that normal muscle and skin tissue, normal tissue surrounding major blood vessels and nerves, as well as healthy blood vessels and nerves themselves, are much less affected than tumor tissue. Normal tissues did show acute, focal, and transitory effects after treatment, but these effects are relatively minor under standard treatment conditions. The severity of these effects increases with the number of electric pulse cycles and applied voltage. The observed histological changes resolved 20 to 40 days after treatment or sooner, even after excessive EP treatment. Thus, B-EPT is distinct from other ablative therapies, such as thermal, cryo, or photodynamic ablation, which equally affect healthy and tumor tissue. In comparison to surgical or radiation therapy, B-EPT also has potential as a tissue-sparing and function-preserving therapy. In clinical studies with over 50 late stage head and neck cancer patients, objective tumor response rates of 55-58%, and complete tumor response rates of 19-30% have been achieved.