Biochemistry of Plasma in Cancer Therapy

Abstract

This chapter summarizes the role of reactive oxygen/reactive nitrogen species (ROS/RNS) in multistep oncogenesis as well as a selection of central features of the composition and antitumor effects of cold atmospheric plasma (CAP) and plasma-activated medium (PAM). It provides a compendium on important ROS/RNS sources and reactions in the context of CAP and PAM interactions with non-malignant as compared to malignant cells. As CAP- and PAM-derived ROS/RNS are directly interacting with the surface of targeted cells, the redox-related elements on the membrane of non-malignant cells, transformed cells (early stage of oncogenesis), and bona fide tumor cells (late stage of oncogenesis) are outlined in detail. Based on this information, the experimentally derived concept of primary singlet oxygen generation from CAP and PAM constituents and their triggering function for sustained and dynamic generation of secondary singlet oxygen by the tumor cells themselves is presented. These data allow presenting a scenario of CAP and PAM action during tumor therapy, in which CAP and PAM are the triggers, whereas the tumor cells themselves are the effectors for the induction of their cell death. Evidence for the selective damage in non-malignant over malignant cells is provided in such a context. This concept will be discussed in relation to existing concepts that are based on the assumption that CAP and PAM already contain the cell death-inducing compound at sufficient concentration to cause the observed effects.