Effects of electrochemotherapy with bleomycin on normal liver tissue in a rat model

Preliminary studies that used electric pulses in vivo to facilitate entry of chemotherapeutic agents into tumour cells resulted in a 69% complete response rate for hepatocellular carcinoma in rats. This success motivated a focused investigation to define the adverse effects of this treatment on normal liver tissue. Bleomycin doses ranging from 0.5 to 2.5 U and electric fields from 500 to 2250 V/cm were investigated. Electrical treatment was administered using an array of six needles arranged in a circular pattern. Necrosis and four other histological parameters were examined 14 and 56 days after treatment. Results indicated that treatment effects were localised to the volume of treated tissue. These parameters, at both time points, were not significantly altered for liver tissue that was treated with all drug doses and electric fields of 1250 V/cm and below. Only the combination of more intense electric pulses with bleomycin produced adverse histological events in the form of localised liver necrosis at day 14. These effects were not visible at day 56. Liver function was normal through all of the treatment except for an elevation of several enzymes 1 day post-treatment.

Treatment of hepatocellular carcinoma in a rat model using electrochemotherapy

The effectiveness of antineoplastic agents has been augmented by applying pulsed electric fields directly to tumours after the administration of the drug. This treatment, known as electrochemotherapy (ECT), has been successful for cutaneous malignancies in animal models and in recent clinical trials. This study was aimed at investigating the applicability of ECT in a surgical setting for hepatocellular carcinomas induced in the livers of rats. Established tumours were injected with bleomycin, and electric pulses were then administered locally. Animals were followed based on tumour volumes and histological samples. Dose response data were obtained for both electric field intensity and bleomycin. Complete response rates for animals treated with electrochemotherapy ranged from 26.67% to 93.33 and were durable. In contrast, tumours that received no treatment, pulses only or drug only responded minimally. This supports the feasibility of using a ECT as a modality for treating hepatocellular carcinoma.

In vivo electroporation of plasmids encoding GM-CSF or interleukin-2 into existing B16 melanomas combined with electrochemotherapy induces long-term antitumour immunity

When cancer cells, including melanoma cells, are genetically altered to secrete cytokines, irradiated and injected into subjects, long-term antitumour immunity is induced. Optimally, existing melanomas induced to produce cytokines in vivo could stimulate this same immune response. Although in vivo electroporation enhances plasmid expression, electroporation of plasmids encoding granulocyte-monocyte colony stimulating factor (GM-CSF) and interleukin-2 (IL2) into B16 mouse melanomas did not significantly alter tumour growth at the concentration tested. Electrochemotherapy, which causes short-term, complete regressions of treated tumour but no resistance to challenge, was combined with plasmid delivery. The combination treatment resulted in the induction of long-term immunity to recurrence and resistance to challenge in up to 25% of mice.

Electrically mediated plasmid DNA delivery to hepatocellular carcinomas in vivo

Gene therapy by direct delivery of plasmid DNA has several advantages over viral gene transfer, but plasmid delivery is less efficient. In vivo electroporation has been used to enhance delivery of chemotherapeutic agents to tumors in both animal and human studies. Recently, this delivery technique has been extended to large molecules such as plasmid DNA. Here, the successful delivery of plasmids encoding reporter genes to rat hepatocellular carcinomas by in vivo electroporation is demonstrated.

Toxicity of anticancer agents mediated by electroporation in vitro

Electroporation is a physical event that temporarily reduces cell membrane barrier properties. Diminished membrane barrier properties are achieved by exposing cells to pulsed electric fields. When a cell has been treated with electric fields it is possible for extracellular agents to gain access to the cell interior. This process has been used in vivo to increase the uptake of chemotherapeutic agents by tumor cells which results in dramatically higher response rates than when drug is used alone. This type of treatment is called electrochemotherapy (ECT); bleomycin is most often used as the drug for this type of treatment. It was hypothesized that electroporation could be used to augment the cytotoxicity of other anticancer agents. Therefore, this study was performed in order to screen 44 different combinations of drug and cell type in vitro to identify drugs that may have higher cytotoxicity when combined with electroporation. Results from seven cell types indicate that the IC50 of bleomycin can be reduced by a factor of 100-5000 when electroporation is used to facilitate internalization. The IC50 values of cisplatin and carboplatin could be reduced by factors ranging from 3 to 13 in six different cell lines as a result of electroporation. These IC50 reductions in multiple cell lines suggest that cisplatin and carboplatin may be effective in vivo as part of ECT treatment.

Electrically mediated drug delivery for treating subcutaneous and orthotopic pancreatic adenocarcinoma in a hamster model

BACKGROUND

Current therapies for pancreatic adenocarcinoma only benefit a fraction of those diagnosed with this disease. New strategies for improving treatment are clearly needed. This study investigated the use of electrically mediated drug delivery for the treatment of pancreatic adenocarcinoma in a hamster model.

MATERIALS AND METHODS

Hamster PC-1 pancreatic adenocarcinoma cells and Golden Syrian hamsters were used as a model.

RESULTS

In vitro testing indicated that bleomycin was more effective than Cisplatin and Doxorubicin when delivered using pulsed electric fields. Treatment of subcutaneous tumors with bleomycin and electric fields resulted in a 100 percent complete response rate. No effect was observed when either drug or pulses were used alone. Treatment of tumors induced in the gland resulted in a 25 percent complete response rate.

CONCLUSIONS

Electrochemotherapy was highly effective for subcutaneous tumors. There was also a significant antitumor effect for the more complex and clinically relevant intraoperative treatment of tumors in the pancreas.