Electrochemotherapy with intravenous bleomycin injection: an observational study in superficial squamous cell carcinoma in cats

The aim of this study was to evaluate the efficacy and safety of electrochemotherapy (ECT) with bleomycin for treatment of squamous cell carcinoma (SCC) in cats. Between March 2008 and October 2011, 11 cats with 17 superficial SCC nodules in different clinical stages (ranging from Tis to T4), located on nasal planum (6/11), pinnae (3/11) and both locations (2/11), were included in a prospective non-randomised study. Sixteen of 17 SCC nodules were treated with ECT (15/16 with single session and in one case with two sessions); one nodule was surgically removed. Altogether, complete response (CR) was achieved for 81.8% (9/11) cats and 87.5% (14/16) nodules, lasting from 2 months up to longer than 3 years. Only 2/9 cats in which CR was initially observed, had recurrence 2 and 8 months after the ECT procedure. In the remaining two cats with highly infiltrative spread into adjacent tissues, progression of the disease was observed, despite ECT, and both were euthanased 4 and 5 months after the procedure. ECT in cats was well tolerated and no evident local or systemic side effects were observed. The results of this study suggest that ECT is a highly effective and safe method of local tumour control of feline cutaneous SCCs. It should be considered as an alternative treatment option, especially when other treatment approaches are not acceptable by the owners, owing to their invasiveness, mutilation or high cost.

Multiple delivery of siRNA against endoglin into murine mammary adenocarcinoma prevents angiogenesis and delays tumor growth

Endoglin is a transforming growth factor-β (TGF- β) co-receptor that participates in the activation of a signaling pathway that mediates endothelial cell proliferation and migration in angiogenic tumor vasculature. Therefore, silencing of endoglin expression is an attractive approach for antiangiogenic therapy of tumors. The aim of our study was to evaluate the therapeutic potential of small interfering RNA (siRNA) molecules against endoglin in vitro and in vivo. Therapeutic potential in vitro was assessed in human and murine endothelial cells (HMEC-1, 2H11) by determining endoglin expression level, cell proliferation and tube formation. In vivo, the therapeutic potential of siRNA molecules was evaluated in TS/A mammary adenocarcinoma growing in BALB/c mice. Results of our study showed that siRNA molecules against endoglin have a good antiangiogenic therapeutic potential in vitro, as expression of endoglin mRNA and protein levels in mouse and human microvascular endothelial cells after lipofection were efficiently reduced, which resulted in the inhibition of endothelial cell proliferation and tube formation. In vivo, silencing of endoglin with triple electrotransfer of siRNA molecules into TS/A mammary adenocarcinoma also significantly reduced the mRNA levels, number of tumor blood vessels and the growth of tumors. The obtained results demonstrate that silencing of endoglin is a promising antiangiogenic therapy of tumors that could not be used as single treatment, but as an adjunct to the established cytotoxic treatment approaches.

Radiosensitizing effect of intratumoral interleukin-12 gene electrotransfer in murine sarcoma

Background

Interleukin-12 (IL-12) based radiosensitization is an effective way of tumor treatment. Local cytokine production, without systemic shedding, might provide clinical benefit in radiation treatment of sarcomas. Therefore, the aim was to stimulate intratumoral IL-12 production by gene electrotransfer of plasmid coding for mouse IL-12 (mIL-12) into the tumors, in order to explore its radiosensitizing effect after single or multiple intratumoral gene electrotransfer.

Methods

Solid SA-1 fibrosarcoma tumors, on the back of A/J mice, were treated intratumorally by mIL-12 gene electrotransfer and 24 h later irradiated with a single dose. Treatment effectiveness was measured by tumor growth delay and local tumor control assay (TCD₅₀ assay). With respect to therapeutic index, skin reaction in the radiation field was scored. The tumor and serum concentrations of cytokines mIL-12 and mouse interferon γ (mIFNγ) were measured. Besides single, also multiple intratumoral mIL-12 gene electrotransfer before and after tumor irradiation was evaluated.

Results

Single intratumoral mIL-12 gene electrotransfer resulted in increased intratumoral but not serum mIL-12 and mIFNγ concentrations, and had good antitumor (7.1% tumor cures) and radiosensitizing effect (21.4% tumor cures). Combined treatment resulted in the radiation dose-modifying factor of 2.16. Multiple mIL-12 gene electrotransfer had an even more pronounced antitumor (50% tumor cures) and radiosensitizing (86.7% tumor cures) effect.

Conclusions

Single or multiple intratumoral mIL-12 gene electrotransfer resulted in increased intratumoral mIL-12 and mIFNγ cytokine level, and may provide an efficient treatment modality for soft tissue sarcoma as single or adjuvant therapy to tumor irradiation.

Endoglin silencing has significant antitumor effect on murine mammary adenocarcinoma mediated by vascular targeted effect

New targets and therapeutic approaches for vascular targeted strategies in oncology are continuously explored. Endoglin, a co-receptor of TGF-β, is a known target, however, its silencing with vector-based RNA interference technology has not been evaluated yet. Therefore, in our study, we assembled plasmid DNA coding for shRNA against endoglin, and used gene electrotransfer as a delivery method to determine its antitumor and vascular targeted effects. In vitro and in vivo data provide evidence of vascular targeted effects of endoglin silencing. The vascular targeted action of endoglin silencing could be described as a result of two separated effect; antiangiogenic and vascular disrupting effect. This was first supported by in vitro data; predominantly by reduction of proliferation and tube formation of endothelial cells. In the TS/A murine mammary carcinoma model, in which the tumor cells do not express endoglin, reduced tumor growth and number of vessels were observed. Quick destruction of existing activated blood vessels at the site of tumor cells' injection and sustained growth of tumors afterwards was observed in tumors that were growing in dorsal window chamber by intravital microscopy. This observation supports both vascular disrupting and antiangiogenic action. In conclusion, the results of our study provide evidence of endoglin as a valid target for cancer therapy and support further development of plasmid shRNA delivery, which have prolonged antitumor effect, especially in combined schedules.

Electrochemotherapy with bleomycin is effective in BRAF mutated melanoma cells and interacts with BRAF inhibitors

BACKGROUND

The aim of the study was to explore the effectiveness of electrochemotherapy (ECT) during the treatment of melanoma patients with BRAF inhibitors. Its effectiveness was tested on BRAF mutated and non-mutated melanoma cells in vitro and in combination with BRAF inhibitors.

MATERIALS AND METHODS

ECT with bleomycin was performed on two human melanoma cell lines, with (SK-MEL-28) or without (CHL-1) BRAF V600E mutation. Cell survival was determined using clonogenic assay to determine the effectiveness of ECT in melanoma cells of different mutation status. Furthermore, the effectiveness of ECT in concomitant treatment with BRAF inhibitor vemurafenib was also determined in BRAF mutated cells SK-MEL-28 with clonogenic assay.

RESULTS

The survival of BRAF V600E mutated melanoma cells was even lower than non-mutated cells, indicating that ECT is effective regardless of the mutational status of melanoma cells. Furthermore, the synergistic interaction between vemurafenib and ECT with bleomycin was demonstrated in the BRAF V600E mutated melanoma cells.

CONCLUSIONS

The effectiveness of ECT in BRAF mutated melanoma cells as well as potentiation of its effectiveness during the treatment with vemurafenib in vitro implies on clinical applicability of ECT in melanoma patients with BRAF mutation and/or during the treatment with BRAF inhibitors.

Gene Electrotransfer of Plasmid with Tissue Specific Promoter Encoding shRNA against Endoglin Exerts Antitumor Efficacy against Murine TS/A Tumors by Vascular Targeted Effects

Vascular targeted therapies, targeting specific endothelial cell markers, are promising approaches for the treatment of cancer. One of the targets is endoglin, transforming growth factor-β (TGF-β) co-receptor, which mediates proliferation, differentiation and migration of endothelial cells forming neovasculature. However, its specific, safe and long-lasting targeting remains the challenge. Therefore, in our study we evaluated the transfection efficacy, vascular targeted effects and therapeutic potential of the plasmid silencing endoglin with the tissue specific promoter, specific for endothelial cells marker endothelin-1 (ET) (TS plasmid), in comparison to the plasmid with constitutive promoter (CON plasmid), in vitro and in vivo. Tissue specificity of TS plasmid was demonstrated in vitro on several cell lines, and its antiangiogenic efficacy was demonstrated by reducing tube formation of 2H11 endothelial cells. In vivo, on a murine mammary TS/A tumor model, we demonstrated good antitumor effect of gene electrotransfer (GET) of either of both plasmids in treatment of smaller tumors still in avascular phase of growth, as well as on bigger tumors, already well vascularized. In support to the observations on predominantly vascular targeted effects of endoglin, histological analysis has demonstrated an increase in necrosis and a decrease in the number of blood vessels in therapeutic groups. A significant antitumor effect was observed in tumors in avascular and vascular phase of growth, possibly due to both, the antiangiogenic and the vascular disrupting effect. Furthermore, the study indicates on the potential use of TS plasmid in cancer gene therapy since the same efficacy as of CON plasmid was determined.

Electrotransfer of Plasmid DNA Encoding an Anti-Mouse Endoglin (CD105) shRNA to B16 Melanoma Tumors with Low and High Metastatic Potential Results in Pronounced Anti-Tumor Effects

Endoglin overexpression is associated with highly proliferative tumor endothelium and also with some tumors, including melanoma. Its targeting has anti-tumor effectiveness, which can also be obtained by RNA interference. The aim of our study was to explore the anti-tumor effectiveness of endoglin silencing by electrotransfer of plasmid DNA encoding short hairpin RNA against endoglin in two murine B16 melanoma variants with different metastatic potential on cells, spheroids and subcutaneous tumors in mice. The results demonstrate that endoglin silencing with gene electrotransfer reduces the proliferation, survival and migration of melanoma cells and also has anti-tumor effectiveness, as the therapy resulted in a high percentage of tumor cures (23% and 58% on B16F1 and B16F10 tumors, respectively). The effectiveness of the therapy correlated with endoglin expression in melanoma cells; in vitro the effects were more pronounced in B16F1 cells, which express more endoglin than B16F10. However, the opposite was observed in vivo in tumors, where there was a higher expression of endoglin and better anti-tumor effectiveness in the B16F10 tumor. In conclusion, targeting endoglin for the treatment of melanoma seems to be a concept worthy of further exploration due to the increased therapeutic effect of the therapy based on simultaneous vascular targeting and its direct effect on tumor cells.

Abstract 1381: The vascular targeted and antitumor effects of gene electrotransfer of plasmid silencing endoglin with tissue specific and constitutive promoter

Endoglin, the transforming growth factor-β (TGF-β) co-receptor, mediates proliferation, differentiation and migration of endothelial cells forming neovasculature. It is promising target for vascular targeted therapies for the treatment of cancer, although its specific, safe and long-lasting targeting remains the challenge. One of the options for targeted and prolonged silencing is gene electrotransfer (GET) of plasmid DNA encoding shRNA against endoglin. In our study we used two plasmid DNAs; one with tissue specific promoter for endothelial cells (TS plasmid) and the other with constitutive promoter (CON promoter). In vitro, we evaluated the transfection efficacy using flow cytometry measurement of transfected cells and determined the vascular targeted effects by tube formation assay. The therapeutic potential of the GET of plasmids and comparison of theirs efficacies in vitro was obtained by measuring tumor growth and by analyzing histological sections for determining area of necrosis and a number of activated blood vessels.

In vitro, we demonstrated the tissue specificity of TS plasmid on several cell lines, and the antiangiogenic efficacy of GET of either of both plasmids, as reduced tube formation of 2H11 endothelial cells. In vivo, on a murine mammary TS/A tumor model, we demonstrated good antitumor effect of GET of either of both plasmids in treatment of smaller tumors in avascular phase of growth, as well as on bigger tumors, already well vascularized, possibly due to both, the antiangiogenic and vascular disrupting effect. In order to support that, the histological analysis has demonstrated an increase in necrosis and a decrease in the number of blood vessels in therapeutic groups. Therefore, using GET of TS plasmid we were able to demonstrate that it is specific, safe and has quite the same efficacy as the GET of CON plasmid. Therefore, our approach can represent a novel alternative to other therapeutic approaches that aim at silencing endoglin, which represents also an alternative target in VEGF resistant (unresponsive) tumors.

Citation Format: Monika Stimac, Tanja Dolinsek, Ursa Lampreht, Maja Cemazar, Gregor Sersa. The vascular targeted and antitumor effects of gene electrotransfer of plasmid silencing endoglin with tissue specific and constitutive promoter. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1381. doi:10.1158/1538-7445.AM2015-1381

Abstract 5119: Mechanisms associated with blood flow modifying effects of electric pulses used for electrochemotherapy on normal and tumor blood vessels

Electropermeabilization/electroporation (EP) is a physical method that by applying external electric pulses to cells increases cell membrane permeability and thus enables the introduction of molecules into the cells. Nowadays, it is used in treatment of tumors, where its benefits are exploited in electrochemotherapy (ECT). In vivo EP also modifies blood flow, resulting in a decreased blood flow and increased permeability of blood vessel walls; whereas ECT has a vascular disrupting effect. The aim of our study was to evaluate the effects of EP on normal blood vessels and the effects of EP and ECT with bleomycin on tumor vasculature with the use of in vivo microscopy.

The effects of pulse parameters used for ECT (8 pulses, 1300 V/cm, 100 μs, 1 Hz) on normal blood vessels were determined via a dorsal skinfold window chamber (DWC) with intravital two-photon microscopy after in vivo labelling of CD31 with fluorescently labeled antibodies. Furthermore, 70 kDa fluorescently labeled dextrans was used to visualize the increased permeability of blood vessel walls. Additionally, Fluorescence Lifetime Imaging (FLIM) was used to determine the stability of the used fluorochrome. In tumors the effects of ECT pulse parameters on tumor blood vessels after EP or ECT with bleomycin were determined using 70 kDa fluorescently labeled dextrans either with two-photon or widefield intravital microsocopy via DWC. Solid mouse sarcoma SA-1 tumors were induced by a subcutaneous injection of dense cell suspension into the area of DWC in mice and an intravenous injection of bleomycin (100 μg/mouse) was performed 3 min before the application of electric pulses.

EP resulted in immediate constriction of the affected normal blood vessels and in a rapid increase of vascular permeability. This was accompanied by the change of the endothelial cells’ shape and a decrease of CD31 labelling in the cell-to-cell junctions. In vivo 3D FLIM showed no difference in the lifetime of the used fluorochrome before and after EP. When electric pulses or ECT were applied to tumors the increase in vascular permeability and the constriction of tumor blood vessels were not as pronounced as in normal blood vessels. However, there was a complete vascular lock that lasted for more than 30 min. Furthermore, ECT had a differential vascular disrupting effect on tumor blood vessels, leaving the larger normal blood vessels surrounding the tumors functional after the therapy.

In conclusion, the results of our study provide direct in vivo evidence of the difference in vascular effects of electric pulses used for ECT in normal and tumor blood vessels, show the response of normal endothelial cells to EP with two-photon microscopy and 3D FLIM, and provide evidence of the differential vascular disrupting action of ECT.

Citation Format: Bostjan Markelc, Elisabeth Bellard, Gregor Sersa, Tanja Dolinsek, Justin Teissie, Muriel Golzio, Maja Cemazar. Mechanisms associated with blood flow modifying effects of electric pulses used for electrochemotherapy on normal and tumor blood vessels. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5119. doi:10.1158/1538-7445.AM2015-5119