RHBDD2 Confers Insensitivity of Esophageal Squamous Cell Carcinoma to Cisplatin by Inhibiting Ferroptosis Through the Wnt3a/β-Catenin/FTH1 Axis.

As a pseudoprotease member of the rhomboid family, rhomboid domain containing 2 (RHBDD2) has been demonstrated to be associated with 5‑FU resistance. Our previous work found that RHBDD2 is also upregulated by cisplatin (DDP) treatment in esophageal squamous cell carcinoma (ESCC). However, the effect of RHBDD2 on DDP sensitivity and the underlying molecular mechanisms remain poorly understood. In this study, we demonstrate that RHBDD2 regulates the sensitivity of ESCC cells to DDP in vitro. In vivo, RHBDD2 knockdown significantly enhanced the antitumor effect of DDP in a subcutaneous xenograft model of ESCC. Enrichment analysis of RNA‑seq data from ESCC cells with RHBDD2 knockdown revealed that RHBDD2 is involved in regulating the biological process of ferroptosis. RHBDD2 inhibited ferroptosis by upregulating ferritin heavy chain 1 (FTH1), a major iron storage protein, and FTH1 knockdown reversed RHBDD2‑induced insensitivity of ESCC cells to DDP in vitro. Mechanistically, RHBDD2 promoted Wnt3a secretion, which in turn inhibited the phosphorylation and ubiquitination of β‑catenin, thereby enhancing β‑catenin nuclear localization and its transcriptional activity. Inhibition of β‑catenin‑mediated transcription by ICG‑001 reversed RHBDD2‑upregulated FTH1 expression and DDP insensitivity in vivo. Furthermore, we found that RHBDD2 mRNA is modified by N6‑methyladenosine (m6A), and its expression can be regulated by the m6A reader insulin‑like growth factor 2 mRNA‑binding protein 2 (IGF2BP2) in ESCC cells. Collectively, our results reveal a novel role for RHBDD2 in inhibiting ferroptosis and inducing DDP insensitivity by upregulating the Wnt3a/β‑catenin/FTH1 axis, which may provide a therapeutic target for improving the efficacy of DDP in ESCC.