Bioinformatics Analysis and Verification of Metabolic Abnormalities in Esophageal Squamous Carcinoma

Background: Although esophageal carcinoma (EC) is one of the most common cancers in the world, details of its pathogenesis remain unclear. Metabolic reprogramming is a main feature of EC. Mitochondrial dysfunction, especially the decrease in mitochondrial complex I (MTCI), plays an important role in the occurrence and development of EC. Objective: The objective of the study was to analyze and validate the metabolic abnormalities and the role of MTCI in esophageal squamous cell carcinoma. Methods: In this work, we collected transcriptomic data from 160 esophageal squamous carcinoma samples and 11 normal tissue samples from The Cancer Genome Atlas (TCGA). The OmicsBean and GEPIA2 were used to conduct an analysis of differential gene expression and survival in clinical samples. Rotenone was used to inhibit the MTCI activity. Subsequently, we detected lactate production, glucose uptake, and ATP production. Results: A total of 1710 genes were identified as being significantly differentially expressed. The Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) enrichment analysis suggested that these differentially expressed genes (DEGs) were significantly enriched in various pathways related to carcinoma tumorigenesis and progression. Moreover, we further identified abnormalities in metabolic pathways, in particular, the significantly low expression of multiple subunits of MTCI genes (ND1, ND2, ND3, ND4, ND4L, ND5, and ND6). Rotenone was used to inhibit the MTCI activity of EC109 cells, and it was found that the decrease in MTCI activity promoted HIF1A expression, glucose consumption, lactate production, ATP production, and cell migration. Conclusion: Our results indicated the occurrence of abnormal metabolism involving decreased mitochondrial complex I activity and increased glycolysis in esophageal squamous cell carcinoma (ESCC), which might be related to its development and degree of malignancy.