Recent reports from our laboratory revealed dysregulation of tryptophan catabolism in leiomyomas, with tumors of African American women expressing more TDO2 (tryptophan 2,3-dioxygenase) mRNA but lower levels of KYNU (L-Kynurenine hydrolase) mRNA as compared to Caucasian women [38, 92]. Here, TDO2 is linked to leiomyoma.