IDO2 and lung carcinoma: Similarly, several human tumor and non-tumor cell lines express IDO2 mRNA, such as the lung cancer cell lines A549 [46], H1650, H2228, H1975, and CALU-3 (our unpublished observations), but also MCF-7 [47], HEK293, HepG2, and CACO2 cell lines derived from tissues other than the lung’s (our unpublished observations and [48]).