Role of PLEKHA7 in promoting radioresistance in esophageal cancer cells via the inhibition of cuproptosis.

BACKGROUND: Esophageal squamous cell carcinoma (ESCC) is a leading cause of cancer-related mortality worldwide, with radiotherapy (RT) being a primary treatment modality. However, radioresistance-induced tumor recurrence significantly limits the effectiveness of RT. The aim of this study is to explore potential strategies to enhance radiosensitivity and reduce the risk of local recurrence in esophageal squamous cell carcinoma. METHODS: Gene expression and clinical data of patients with advanced ESCC were analyzed using The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) databases. According to the expression profiles of 49 cuproptosis-related genes (CRGs), potential regulators of cuproptosis in ESCC were identified using unsupervised consensus clustering analysis, univariate Cox analysis, and least absolute shrinkage and selection operator (LASSO) regression. Western blotting, quantitative reverse transcription polymerase chain reaction (qRT-PCR) and intracellular copper measurement were used to explore the relationship between these genes and cuproptosis. Colony formation assay, Cell Counting Kit 8 (CCK-8) assay, 5-ethynyl-2'-deoxyuridine (EdU) assay, flow cytometry and immunofluorescence assay were performed to explore the efficacy of RT combined with cuproptosis inducers in ESCC. RESULTS: PLEKHA7 was identified as a key regulator of cuproptosis in ESCC, and its expression was reduced in ESCC tissues compared to normal tissues. PLEKHA7 was decreased by elesclomol-CuCl(2) treatment, which led to the intracellular accumulation of copper and cell death via cuproptosis. Ionizing radiation (IR) further induced reactive oxygen species (ROS) production, suppressed the expression of PLEKHA7, and increased cuproptosis. Conversely, PLEKHA7 overexpression suppressed the accumulation of copper and reduced IR-induced cell death, showing its role in maintaining copper homeostasis and radioresistance. CONCLUSIONS: Based on our findings PLEKHA7 appears to be a key radioresistance modulator that inhibits cuproptosis in ESCC. Our findings showed that elesclomol-CuCl(2), a defined inducer of cuproptosis, increased intracellular copper and ROS production, and improved RT efficacy in PLEKHA7-deficient ESCC cells. This treatment represents a promising therapeutic approach for overcoming radioresistance in ESCC patients. Using cuproptosis inducers as radiosensitizers could be particularly helpful for patients with low PLEKHA7 expression and may facilitate precision therapy in ESCC.