The aim of this work was to evaluate the possibility of using cold atmospheric plasma (CAP) for the therapy of head and neck squamous cell carcinoma (HNSCC). For this purpose, in vitro HNO97 and HNO41 carcinoma cells were treated with argon-CAP or helium-CAP by the kINPen 09 or a prototype and compared to an epithelial cell line in order to work out source gas-related differences. By using fetal calf serum (FCS) and Panexin NTA (NTA), two different medium additives were compared. In growth kinetics, a reduction in the number of carcinoma and epithelial cells after CAP treatment was shown. This was followed by a proteomic analysis by 2D-DIGE with mass spectrometric identification of proteins with altered amounts compared to corresponding gas controls. The treated samples were divided into clusters by a principal component analysis (PCA) of regulated proteins. The separation was dependent on the serum used, source gas and CAP treatment in descending effect size. Regulatory proteins and molecular functions were identified using Ingenuity Pathway Analysis (IPA). The regulation of p53, HSF1 and TGF- b and the associated influence on the stress response to unfolded proteins, mitochondrial membrane permeability and apoptosis were demonstrated. By depicting the regulated proteins in networks, the influence of CAP on the MAPK-ERK pathway could be identified as a central component of the effect. After analyzing the protein changes, a possible influence on heat shock protein 27 (HSP27) ...