HOCl sensitivity associates with a reduced p53 transcriptional network and calreticulin expression in 25 human cancer cell lines

Abstract

Reactive oxygen species (ROS) play roles in physiological processes and pathological conditions. Higher ROS levels induce oxidative distress and cytotoxic responses, such as chronic inflammatory conditions and cancer. While the cellular responses of various cell types to cytotoxic pro-oxidative conditions have been well studied in the past decades, much less is known about the cellular gene and expression profiles that are a priori associated with subsequent cellular demise to oxidative stress. To this end, we used 25 human cancer cell lines of different origins and established the inhibitory concentration (IC₂₅) of hypochlorous acid (HOCl), an oxidant readily produced by neutrophils frequently present in many inflamed tissues, including cancer. The HOCl sensitivity varied throughout the 25 cell lines investigated, showing a more than 5-fold difference between the most sensitive and resistant types. In parallel, we investigated untreated cells and their basal gene expression using transcriptomic microarray and performed correlation analyses to HOCl IC₂₅ values of all cell lines. Transcriptomic analyses and functional classification of significant correlating genes revealed reduced expression of tumor protein p53 signaling network members, including BAX, CDKN1A (p21), and BTG2, as well as the p53 gene (TP53) itself to associate with cell line sensitivity to HOCl toxicity. Further, baseline surface membrane expression analysis of 33 inflammation- and redox-related molecules identified nitric oxide (NO) synthase 2 and the ER-stress-associated chaperone calreticulin to correlate significantly with HOCl resistance. We identified targets associated with HOCl sensitivity. Nevertheless, further studies are needed to map gene and protein expression patterns associated with oxidative stress-induced cytotoxicity.