Calcium Electrochemotherapy for Tumor Eradication and the Potential of High-Frequency Nanosecond Protocols

Abstract: Calcium electroporation (CaEP) is an innovative approach to treating cancer, involving the internalization of supraphysiological amounts of calcium through electroporation, which leads to cell death. CaEP enables replacement of the usage of chemotherapeutics (e.g., bleomycin). Here we present a standard microsecond (μsCaEP) and novel high-frequency nanosecond protocols for calcium electroporation (nsCaEP) for the elimination of carcinoma tumors in C57BL/6J mice. We show the efficacy of CaEP to eliminate tumors and increase their survival rates in vivo. The antitumor immune response after the treatment was observed by investigating immune cell populations in tumors, spleens, lymph nodes, and blood as well as assessing antitumor antibodies. CaEP treatment resulted in an increased percentage of CD4⁺ and CD8⁺ central memory T cells and decreased tumor-associated and splenic myeloid-derived suppressor cells (MDSC). Also, increased levels of antitumor IgG antibodies after CaEP treatment were detected. The experimental results demonstrated that the administration of CaEP led to tumor growth delay, increased survival rates, and stimulated immune response, indicating a potential synergistic relationship between CaEP and immunotherapy.