AR and cancer: Moreover, these contrasting roles of TR4 to either enhance or suppress tumor metastasis are not unique, since other nuclear receptors such as androgen receptor also play opposite roles in various cancers, namely, functioning as a suppressor in HCC [26, 27] and prostate cancer [28, 29] metastasis but as a stimulator promoting bladder cancer [30, 31] and renal cancer [32] metastasis.