Nanosecond pulsed electric fields inhibit breast cancer development and suppress tumor blood vessel growth

Breast cancer is one of the most threatening malignant tumors among women, the incidence of which is rising year by year. Despite of early screening and improvement in breast cancer management that have increased the 5-year survive rate, the requirement for novel and more efficient therapy for breast cancer is still quite urgent. In the recent decades, nanosecond pulsed electric fields, known as NsPEFs, have been proved to be able to induce cell apoptosis and tumor inhibition in various cancers. In this study, we established breast cancer animal model with MCF-7 cell line on Balb/c nude mice. An electric field over 30kV/cm was generated between to the two pads of the clamp, where the tumor was placed. Tumors were treated with nsPEFs on three consecutive days, and day 0 was set as the day when nsPEFs treatment was finished. Within 2 weeks after treatment, it was observed that tumor growth was significantly inhibited. The average volume and weight of pulsed tumors was almost 1/9 of that of unpulsed tumors. Morphological changes were observed in a 3.0T clinical magnetic resonance imaging (MRI) system with an own-made surface coil on day0, day7 and day14, which showed the shrinkage of the tumors. Apoptosis and hemorrhagic necrosis in tumor cells were inspected after nsPEFs treatement by H&E staining. Immuno-histological tests indicated VEGF expression in tumor cells was strongly suppressed. Tumor blood vessel density was calculated and found decreased after nsPEFs treatment. The results suggest nsPEFs can inhibit breast cancer development and suppress tumor blood vessel growth, which may serve as a novel therapy for breast cancer in the future.