EMT6/P

Cytotoxicity Study of CeO₂@PQQ NPs on Mouse Fibroblasts (L929) and Mouse Adenocarcinoma Cells (EMT6/P)

Ionising radiation, a critical component of cancer radiotherapy, unfortunately induces oxidative stress in cancerous cells as well as normal ones, disrupting vital functions when ROS levels are not properly monitored. The problem has prompted research into novel antioxidants such as cerium oxide nanoparticles (CeO₂ NPs), which act as pH-sensitive redox regulators, and pyrroloquinoline quinone (PQQ), which modulates mitochondrial function. Zamyatina's team precipitated CeO₂@PQQ NPs, and measured its physical and catalytic characteristics. They then tested the cytotoxicity of cerium oxide-pyrroloquinoline quinone nanoparticles (CeO₂@PQQ NPs) against mouse fibroblasts (L929) and mouse adenocarcinoma cells (EMT6/P) to determine non-toxic concentrations for future studies. Based on MTT measurements, they observed that 10 M CeO₂@PQQ NPs significantly inhibited NADPH-dependent oxidoreductase activity in L929 cells by 35% after 48 hours; 50 M and 100 M NPs reduced activity by 51% (Fig. 1A). Co-incubation at 0.1 to 2 μM had minimal effects, but at 20 μM, viability sharply decreased by 64%, and by 87% and 81% at 50 and 100 μM, respectively. In EMT6/P cells, metabolic activity remained high up to 20 μM but decreased significantly at higher concentrations (Fig. 1B). A 20 μM concentration reduced metabolic activity for both cell types to the IC₅₀ value, with 50 and 100 μM proving highly toxic even at 48 and 72 hours, decreasing viability by 82% and 96%, respectively.

Fig. 1. Cell viability of L929 (A) and EMT6/P (B) cells (Zamyataina EA, Goryacheva OA, et al., 2024).

Cytotoxicity of Binary Proton Therapy of Mouse Mammary Carcinoma Cells (EMT6/P line) Using Targeted Gold Nanoparticles

Proton therapy is an advanced technique in radiation oncology due to its precision in targeting tumors located in radiation-sensitive tissues. However, delivering nanoparticles effectively to the tumor site remains challenging. A promising target for targeting is the FRα isoform of the folate receptor. Therefore, Filimonova's team aims to explore the use of gold nanoparticles, specifically Au-PEG-FA nanoparticles, to enhance the efficacy of proton therapy by targeting the folate receptor. To assess the enhancement of proton therapy with nanoparticles, cytotoxicity was tested on mouse mammary carcinoma cells (EMT6/P line). Cells were treated with gold nanoparticles and incubated for 16 hours before irradiation at the Prometheus proton therapy complex in Russia, with a proton energy of 160.5 MeV and beam homogeneity of at least 98% at 95% isodose. Eight days post-irradiation, a significant reduction in clonogenic activity was observed with binary therapy (Fig. 2). Au-PEG nanoparticles (10–50 μg/mL) did not reduce cell colony formation, indicating high biocompatibility. Cells showed a dose-dependent reduction in colonies by 25% and 50% at 2 and 4 Gy, respectively. Preincubation with 50 μg/mL Au-PEG and 2 Gy co-irradiation resulted in a fourfold colony decrease versus non-irradiated controls (Fig. 2). Preincubation with 25 or 50 μg/mL nanoparticles and 4 Gy irradiation led to complete cancer colony elimination, demonstrating Au-PEG's biocompatibility and radiosensitizing effect at 2–4 Gy in vitro.

Fig. 2. Clonogenic analysis of EMT6/P adenocarcinoma cells after proton beam irradiation in the presence of Au-PEG nanoparticles (Filimonova MV, Kolmanovich DD, et al., 2024).