Tazarotene-Induced Gene 2 Promotes Melanoma Cell Death via the Activation of Endoplasmic Reticulum Stress.

BACKGROUND: Tazarotene-induced gene 2 (TIG2), also known as retinoic acid receptor responder 2 (RARRES2), encodes the secreted protein TIG2, also known as chemerin, which is involved in immune regulation and metabolism. However, its role in melanoma remains unclear. METHODS: TIG2 expression was analyzed using The Cancer Genome Atlas, Genotype-Tissue Expression, OncoDB, and melanoma tissue cDNA arrays. To evaluate its effects on cell viability and death, TIG2 was overexpressed in A2058 and A375 melanoma cells. RNA sequencing (RNA-seq), qPCR, and Western blotting were performed to identify TIG2-regulated genes and signaling pathways. The involvement of chemokines and endoplasmic reticulum (ER) stress was further examined using the C-X-C motif chemokine ligand 10 (CXCL 10)/CXCL11 and the ER stress inhibitor tauroursodeoxycholic acid (TUDCA). RESULTS: TIG2 expression was reduced in melanoma and other skin cancers. TIG2 overexpression significantly reduced cell viability and induced cell death. RNA-seq analysis showed that TIG2 downregulated CXCL10, CXCL11, and CCL2 while upregulating ER stress-related genes such as HERPUD1 and DDIT3. Exogenous CXCL10 or CXCL11 did not reverse TIG2-mediated effects, whereas TUDCA partially restored cell viability and reduced cell death. CONCLUSIONS: These findings suggest that TIG2 suppresses melanoma cell growth by activating ER stress and modulating immune-related chemokines, highlighting its potential therapeutic relevance.