TDO2（tryptophan 2，3-dioxygenase），癌症关联基因，基因ID：6999，该基因编码血红素酶，在色氨酸代谢中起关键作用，通过催化酪氨酸途径的第一步和限速步骤。编码蛋白的活性增加和随后的酪氨酸生成也可能通过抑制抗肿瘤免疫反应而在癌症中发挥作用，该基因的单核苷酸多态性可能与孤独症有关。[由RefSeq提供，2012年2月]This gene encodes a heme enzyme that plays a critical role in tryptophan metabolism by catalyzing the first and rate-limiting step of the kynurenine pathway. Increased activity of the encoded protein and subsequent kynurenine production may also play a role in cancer through the suppression of antitumor immune responses， and single nucleotide polymorphisms in this gene may be associated with autism. [provided by RefSeq， Feb 2012]。