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

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.

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).

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.

These findings suggest that TIG2 suppresses melanoma cell growth by activating ER stress and modulating immune-related chemokines, highlighting its potential therapeutic relevance.