Loss of transcription factor RARG activates PI3K/AKT signaling via downregulating PTHLH to promote esophageal squamous cell carcinoma progression

Esophageal squamous cell carcinoma (ESCC) is one of the most prevalent malignancies worldwide, characterized by high incidence and mortality. The identification of novel therapeutic targets is therefore urgently needed. However, the expression and functional role of RARG, a putative central carbon metabolism (CCM)-related transcription factor, remain to be fully elucidated. Integrative bioinformatics analysis identified RARG as a downregulated candidate in ESCC. Its expression and prognostic value were assessed by tissue microarray analysis. The functional role of RARG was investigated via CCK-8, colony formation, EdU, wound healing, Transwell, and apoptosis assays in RARG-knockdown and RARG-knockout cells. Furthermore, Western blotting, RNA-seq, ChIP-seq, ChIP-qPCR, co-immunoprecipitation, and rescue experiments were conducted to unravel the molecular mechanisms underlying the observed tumor-suppressive effects of RARG. A 14-gene risk model was established and validated as a robust prognostic signature. Transcription factor RARG was significantly downregulated in ESCC tissues and low RARG expression correlated with poor overall survival. Knockdown or knockout of RARG significantly enhanced proliferation, migration, and invasion while reducing apoptosis. Mechanistic studies revealed PTHLH as a direct transcriptional target of RARG. Furthermore, co-immunoprecipitation assays demonstrated a physical interaction between RARG and PTHLH protein. Loss of RARG activated the PI3K/AKT signaling pathway, and PTHLH overexpression partially rescued the pro-tumorigenic phenotypes induced by RARG deficiency. Our study identifies RARG as a candidate tumor-suppressive transcription factor in ESCC and delineates the RARG-PTHLH-PI3K/AKT regulatory axis in which loss of RARG promotes malignant progression. These results suggest RARG as a potential prognostic biomarker for ESCC.