Efficacy And Mechanism Of Locoregional Ablation Of Breast Cancer In Mice With Novel Nanosecond Pulsed Electric Field

Background and intention:Breast cancer is a kind of malignant tumor that seriously affects women health.Surgery is still the main treatment,but has many complications and affects the beauty.The treatment of breast cancer tends to be minimally invasive.Nanosecond pulsed electric field(ns PEF)is a novel locoregional ablation methodology that has the advantages of small trauma,no thermal injury,no inflammatory reaction,and is suitable for ablation of body surface tumors.In this study,the nanosecond pulses were applied to treat breast cancer by means of in vitro experiments and in vivo models to select the appropriate parameters to verify its efficacy,and to find the dose-response relationship,and to provide basic data for the clinical application of nanosecond pulsed electric field.Methods:(1)4T1 breast cancer cell lines were cultured in vitro and counted after digestion by trypticase in logarithmic growth phase.1×10~5cells/m L suspension cell solution was prepared and placed in an electric shock cup.Fifty pulses of 0 k V/cm,20 k V/cm,30k V/cm,40 k V/cm were set.After ablation,the cells were placed in 96-well plate and100?L per well.The cells were cultured for 24 hours and 48 hours respectively.The optical density(OD)value at 450 nm was measured by CCK-8 test to observe the growth and proliferation of 4T1 cells.(2)4T1 cells in logarithmic growth phase were selected.After ablation with the same electric field intensity and pulse parameters,the apoptosis of tumor cells was detected by flow cytometry after 0 h and 24 h,respectively.(3)Balb/c female mice aged 6-8 weeks were inoculated subcutaneously with 100?L and 5×10~6cells/m L 4T1 cell suspensions below the right mammary gland.The mice were divided into 6 groups after 2 weeks:normal group,tumor control group,surgery group,20 k V/cm pulsed group,25 k V/cm pulsed group and 30 k V/cm pulsed group.Eleven to twelve mice in each group were observed regularly after different treatments.After 14 days,the mice were sacrificed for hematoxylin-eosin staining(HE staining).Tumor sizes and pathological types in mice were compared after ablation with different therapeutic parameters.Results:(1)With the increase of electric field intensity,the optical density(OD)value gradually decreased which meant the total number of living cells decreased gradually.(2)With 50 pulses,the apoptotic rate gradually increased under 0 k V/cm,20 k V/cm,30k V/cm and 40 k V/cm electric field,and 30 k V/cm pulsed field induced the early apoptosis rate highest.(3)The tumors of 20 k V/cm,25 k V/cm and 30 k V/cm pulsed group achieved different degrees of ablation effect.The tumors in 30 k V/cm pulsed group could be completely ablated.Conclusion:Nanosecond pulsed electric field can induce apoptosis,and the ablation effect has a certain dose effect relationship with the electric field intensity.Appropriate electric field parameters can ablate the subcutaneous transplanted tumor of mouse breast cancer effectively.Nanosecond pulsed electric field is a possible means of local ablation and minimally invasive treatment of breast cancer in the future.