ADI‐PEG20, a mycoplasma enzyme converting exogenous arginine to citrulline and ammonia, has shown antitumor effects in many cancer types (Feun et al., 2008; Kelly et al., 2012; Miraki‐Moud et al., 2015; Qiu et al., 2014), yet cancer cells survive after this treatment due to ASS1 re‐expression and undergoing autophagy (Tsai et al., 2012; You et al., 2013). The gene discussed is ASS1; the disease is cancer.