# Calcium Electrochemotherapy and Challenges in Combined Treatment with Dendritic Cell Vaccination

## TL;DR

This study explores combining calcium electrochemotherapy with dendritic cell vaccination to treat tumors, but finds no improvement in survival or immune response.

## Contribution

The study evaluates the novel combination of calcium-based electrochemotherapy with dendritic cell vaccination in a tumor model.

## Key findings

- Calcium electrochemotherapy showed strong antitumor activity and induced immune responses.
- Combining calcium electrochemotherapy with dendritic cell vaccination did not improve therapeutic outcomes.
- Adding cyclophosphamide also failed to enhance survival or immune response.

## Abstract

Background/Objectives: Electrochemotherapy (ECT) is a reliable and potent technique for managing primary tumors; however, significant efforts are being made to characterize and improve the systemic immune response, which is crucial for metastasis prevention. Current evidence suggests that the advancement of ECT will depend on its integration with complementary immunomodulatory methods. Methods: In this study, we examined the combined effects of calcium-based electrochemotherapy (CaECT, 1.3 kV/cm × 100 µs, eight pulses delivered at 1 Hz repetition frequency) with dendritic cell vaccination (DCV). Lewis lung carcinoma (LLC1) was used as a tumor model. We characterized the effects of CaECT alone and in combination with DCV therapy on tumor growth, analyzed the changes in immune cell subpopulations, and studied the humoral immune response dynamics on day 10, 20, and 30. Given the limited effect of DCV, additional experiments were conducted with the chemotherapeutic drug cyclophosphamide (CP), known for its immunomodulatory properties. Results: Although CaECT demonstrated potent antitumor activity and induced a significant immune response, its combination with DCV did not result in enhanced therapeutic efficacy. The combination of CP also failed to improve median survival. Conclusions: It is concluded that CaECT is a promising alternative to standard ECT involving bleomycin or cisplatin. However, further optimization is necessary to enhance the therapeutic synergy of CaECT when combined with DCV.