Effect of calcium electroporation on tumour vasculature

Abstract

Calcium electroporation (CaEP) is a novel anti-tumour treatment that induces cell death by internalization of large quantities of calcium. The anti-tumour effectiveness of CaEP has been demonstrated in vitro, in vivo, and in preliminary clinical trials; however, its effects on the vasculature have not been previously investigated. Using a dorsal window chamber tumour model, we observed that CaEP affected to the same degree normal and tumour blood vessels in vivo, as it disrupted the vessels and caused tumour eradication by necrosis. In all cases, the effect was more pronounced in small vessels, similar to electrochemotherapy (ECT) with bleomycin. In vitro studies in four different cell lines (the B16F1 melanoma, HUVEC endothelial, FADU squamous cell carcinoma, and CHO cell lines) confirmed that CaEP causes necrosis associated with acute and severe ATP depletion, a picture different from bleomycin with electroporation. Furthermore, CaEP considerably inhibited cell migratory capabilities of endothelial cells and their potential to form capillary-like structures. The finding that CaEP has anti-vascular effects and inhibits cell migration capabilities may contribute to the explanation of the high efficacy observed in preclinical and clinical studies.

A Comprehensive Review of Calcium Electroporation—A Novel Cancer Treatment Modality

“…There was no effect of treatment with calcium alone in concentrations up to 5 mM [18,77,[80][81][82] and even up to 20 mM in the two cell lines where such high concentrations were tested [78]. This is unlike treatment with bleomycin alone where some effect is seen; however, this effect is much less than when combined with electroporation [81,84].…”

“…Calcium electroporation has been tested in vitro in 18 different cell lines (12 cancer cell lines and six normal cell lines of which five are immortalized cells and one is primary cells) [18,[77][78][79][80][81][82][83]. In all tested cell lines, calcium electroporation induced cell death in a dose-dependent manner [18,77,78,80,81] with an IC 50 ranging from 0.4-5.0 mM calcium (in combination with electroporation) in the studies where IC 50 was determined [80,81]. Similar effects can be reached with calcium electroporation as with electrochemotherapy using bleomycin, but no synergistic effect is seen when combining calcium and bleomycin before electroporation [84].…”

Evaluation of Calcium Electroporation for the Treatment of Cutaneous Metastases: A Double Blinded Randomised Controlled Phase II Trial

“…The features of Ca-EP are very similar to ECT: they are both selective to tumour cell, the same pulsing conditions can be used for both procedures, and both have an anti-angiogenic effect in vitro and in vivo on both normal and tumour blood vessels [9,10]. It has also been demonstrated that Ca-EP initiates a systemic immune response.…”

Calcium electroporation for recurrent head and neck cancer: A clinical phase I study

“…Trials using calcium electroporation both in vivo, in vitro, and in clinical trials have demonstrated cell necrosis on different tumor histologies . Additionally, recent studies testing calcium electroporation on different tumor lines against normal cells showed an increased effect on tumor cells indicating that normal tissue surrounding the tumor would be less affected by the treatment .…”

“…20 Trials using calcium electroporation both in vivo, in vitro, and in clinical trials have demonstrated cell necrosis on different tumor histologies. 1,18,21,22 Additionally, recent studies testing calcium electroporation on different tumor lines against normal cells showed an increased effect on tumor cells indicating that normal tissue surrounding the tumor would be less affected by the treatment. 20,[23][24][25][26] A new clinical trial randomizing calcium electroporation against ECT on small skin metastases has shown calcium electroporation to have a similar objective response rate compared to ECT with only limited side effects.…”