Figure S3. Tumor necrosis after treatment with different doses of calcium electroporation MDA-MB231 (human breast cancer) tumors treated with different doses of calcium electroporation: 168 mM CaCl2 injected in a volume equivalent to 20% - 80% of tumor volume and 100 - 500 mM CaCl2 injected in a volume equivalent to half the tumor volume. Calcium concentration is shown per tumor volume. Fraction of necrosis was estimated by stereological point counting of tumors removed 2 days after treatment. Each data point is shown together with linear regression for tumors treated with or without electroporation. Data points for controls are shown in the left panel in grey symbols. Ranges for controls, samples treated with electroporation, and treated without electroporation is shown left of the graph. EP = electroporation. n = 4-5 for treated and n = 3 for untreated/sham treated.
ARTICLE ABSTRACT
Calcium electroporation may offer a simple general tool for anticancer therapy. Transient permeabilization of cancer cell membranes created by applying short, high-voltage pulses in tumors enables high calcium influxes that trigger cell death. In this study, we compared the relative sensitivity of different human tumor models and normal tissues to calcium electroporation. Plasma membrane Ca2+-ATPase (PMCA) protein expression was confirmed in vitro in all cancer cell lines and normal primary dermal fibroblasts studied. In all tumor types tested in vivo, calcium electroporation effectively induced necrosis, with a range of sensitivities observed (36%–88%) 2 days after treatment. Necrosis was induced using calcium concentrations of 100–500 mmol/L and injection volumes 20%–80% of tumor volume. Notably, only limited effects were seen in normal tissue. Calcium content increased >7-fold in tumor and skin tissue after calcium electroporation but decreased in skin tissue 4 hours after treatment to levels comparable with untreated controls, whereas calcium content endured at high levels in tumor tissue. Mechanistic experiments in vitro indicated that calcium influx was similar in fibroblasts and cancer cells. However, we observed decreased PMCA expression in cancer cells compared with fibroblasts, offering a potential explanation for the different calcium content in tumor cells versus normal tissues. Overall, our results suggest that calcium electroporation can elicit a rapid and selective necrosis of solid tumors, with limited deleterious effects on surrounding normal tissues. Cancer Res; 77(16); 4389–401. ©2017 AACR.
