Assessing antitumor effects of plasma-activated phosphate buffered saline in breast cancer cell 2D and 3D models

Cold plasma-based therapy shows potential as a new method of tumor reduction, especially beneficial for patients who do not respond positively to conventional therapy or struggle with health complications associated with such treatment. This study investigates the plasma-activated phosphate-buffered saline (PAPBS) that exhibits significant antitumor efficacy against human breast adenocarcinoma cells in a dose-dependent manner. The activation of phosphate-buffered saline (PBS) was performed using a cold atmospheric plasma of streamer corona discharge. By testing PAPBS on both paclitaxel-sensitive MCF-7 human breast adenocarcinoma cell line and its paclitaxel-resistant subline, MCF-7/PAX, it is shown that PAPBS significantly reduced cell viability and triggered apoptosis in both cell lines after a 1-h incubation. PAPBS effectively inhibited the growth of breast cancer cell 3D physiologically relevant tumor models—spheroids and caused their shrinkage depending on plasma treatment time and the duration of PAPBS exposure. Furthermore, cells in 3D models of resistant breast tumor cells completely lost their viability after 24-h treatment with PAPBS treated 30 min by plasma. These findings indicate that PAPBS enriched by RONS can overcome acquired drug resistance in breast cancer, representing a promising anticancer therapeutic strategy.