Regulation of the KEAP1/NRF2 pathway by claudin-2-targeted lymphoid enhancer-binding factor 1 binding in gastric cancer progression.

This research aimed to examine the clinical relevance and biological function of the tight junction protein claudin-2 (CLDN2) in gastric cancer, along with its regulatory interactions with lymphoid enhancer-binding factor 1 (LEF1) and the Kelch-like ECH-associated protein 1 (KEAP1)/nuclear factor erythroid 2-related factor 2 (NRF2) pathway. Analysis of CLDN2 expression and its prognostic implications in gastric cancer was conducted using data from the Cancer Genome Atlas (TCGA) database. The effects of CLDN2 or LEF1 on gastric cancer (GC) cells were detected by RT-qPCR, Western blot, cell-counting kit-8 (CCK-8), transwell assay, flow cytometry, CO-IP and immunofluorescence assays. The interactions between CLDN2 and LEF1 was predicted and validated using Gene MANIA and GEPIA. The functional association between CLDN2 and LEF1 was analyzed by rescue experiments. In GC tissues, CLDN2 was significantly upregulated and correlated with tumor stage, lymph node metastasis, and poor prognosis, showing elevated levels in young patients (21-40 years old) and individuals infected with Helicobater pylori (H. pylori). CLDN2 silencing inhibited GC cell proliferation, migration and invasion, induced G1-phase cycle block and apoptosis, and decreased cyclin D1 expression. CLDN2 and LEF1 were positively correlated and directly interacted, and suppressing LEF1 hindered the progression of GC. CLDN2 reduced KEAP1 expression and promoted NRF2 protein stability through post-transcriptional regulation. Silencing CLDN2 or LEF1 activated the KEAP1/NRF2 pathway and inhibited downstream p65, IkappaB kinase (IKK) and IκB protein expression. Reducing LEF1 levels counteracted the effects of CLDN2 on GC cell growth and KEAP1/NRF2 pathway. Increased levels of CLDN2, which modulate the LEF1 and KEAP1/NRF2 pathways, are correlated with GC progression and may be used as a marker for poor prognosis.