IDO1 and cancer: These situations can include viral infection (Clavarino et al, 2012b), exposure to high levels of fatty acids during pathogenesis, oxidative stress during inflammation or amino acids starvation, mediated by amino acid–degrading enzymes, such as arginase 1 or IDO, which are induced during infection or cancer development (Munn et al, 2004; Claudio et al, 2013).