Spatial Cell Death and Oxidative Stress Dynamics in Gas Plasma‐Treated Tumor Tissues

Cold physical gas plasma generates various reactive oxygen and nitrogen species and has emerged as potential anticancer treatment. However, its effects on and into tumor tissue are poorly understood. Using three gas plasma‐treated tumor models (in ovo Panc1 pancreas carcinoma tissue, ex vivo CT26 colorectal carcinoma tissue, and in vivo SSC7 squamous carcinoma tissue), apoptosis and tissue penetration, along with stress markers, were analyzed. Across all models, a significant increase in TUNEL‐positive cells was revealed. The extent of apoptosis correlated with the intensity and duration of the gas plasma application, being most pronounced within the tumor periphery. Immunofluorescence quantification of oxidative and nitrosative stress markers, including 8‐hydroxy‐2′‐deoxyguanosine (8‐OHdG) and 3‐nitrotyrosine (3‐NT), showed elevated staining and significant intensity increases. This was particularly notable within the first 500 µm from the tissue surface. Finally, safety assessments were performed based on histopathological analyses of nontumor tissues in a healthy gas plasma‐treated murine skin. While apoptotic events were found to some degree, no significant adverse effects on adjacent healthy tissue, such as necrosis or off‐target tissue damage, were observed within the assessed zones following gas plasma exposure. These findings support a favorable safety profile under the tested conditions, which is a key consideration for future clinical translation.