Synergistic Effects of Ionizing Radiation and Electrochemotherapy for In Vitro Cancer Treatment

Ionizing radiation (IR) and chemotherapy, often employing cisplatin (CIS), are widely used cancer treatment modalities. However, despite their effectiveness, these treatments often cause undesirable side effects due to high drug doses and systemic administration. This study aimed to evaluate the combined effects of IR, CIS, and electroporation (EP) on the viability of Chinese hamster ovary (CHO) cells in vitro. The goal was to determine if combination therapy, utilizing EP for CIS delivery into cells, could reduce the required CIS concentration and thus mitigate side effects while maintaining effective anti-cancer activity. Initially, the efficacy of individual treatments was assessed. Statistically significant CHO cell death was observed starting at an IR dose of 3 Gy, reducing viability to 80%. Increasing the dose to 10 Gy decreased cell viability to 1%. EP was effective from a field strength of 3500 V/cm, reducing viability to 87%, with a maximum field of 4000 V/cm resulting in 58% viability. CIS, without EP, significantly reduced cell viability only at higher concentrations – from 50 µg/ml (85% viability) and 100 µg/ml (76% viability). Subsequent experiments analyzed the effects of combined treatments. The combination of IR and EP did not produce a synergistic effect, with cell death primarily dependent on the IR dose. In contrast, the combination of CIS and EP demonstrated a pronounced synergistic effect. At low CIS concentrations (5 µg/ml) and an EP field of 1500-2500 V/cm, cell viability decreased to ~30%, and at 3000-4000 V/cm to <10%. The combined effect of IR and CIS also resulted in synergistic cell death, particularly at an IR dose of 3 Gy and a CIS concentration of >1 µg/ml, where viability decreased to <10%. Finally, the combination of all three modalities – IR, EP, and CIS – exhibited the most pronounced synergistic effect. Even at low doses of IR (1 Gy), EP (1000 V/cm), and CIS (10 µg/ml), cell viability decreased to 37%, compared to >92% with individual treatments. Increasing the CIS concentration further enhanced cell death. In conclusion, the results of this study demonstrate that combined IR, EP, and CIS therapy exhibits significant anti-cancer potential, allowing for a reduction in CIS concentration and potentially minimizing side effects.