Retinoids act through ligand-dependent transcription factors, retinoid X receptor (RXRs) and retinoic acid receptors (RARs). Tazarotene-induced gene (TIG) proteins, also designated retinoic acid receptor responder proteins or RAR-responsive proteins, can be membrane bound or secreted. TIGs act as tumor suppressor genes in human cancers and are highly expressed in skin, hair follicles and endothelial cells as well as in pancreas, spleen and intestine. TIGs are activated by tazarotene and have been implicated as growth regulators that mediate the growth suppressive effects of retinoids. TIG2 is a secreted protein that is mainly expressed in epidermis, hair follicles and endothelial cells. TIG2 is inhibited in psoriatic lesions and is activated by tazarotene in skin rafts and in epidermis of psoriatic lesions.