TDO2 and ovarian cancer: Expression of tryptophan 2,3-dioxygenase 2 (TDO2), a rate-limiting enzyme in the KYN pathway, is increased in anoikis-resistant TNBC (9–11) and ovarian cancer cells (12) grown under anchorage-independent conditions compared with two-dimensional culture, and furthermore, anchorage-independent survival is dependent on TDO2 activity (13).