Transposable elements (TEs) are major contributors to genome plasticity and can reshape gene regulation through stress-responsive activation and the formation of TE-gene chimeric transcripts. Although therapeutic stress is known to perturb transcriptional networks in cancer cells, its impact on canonical TE transcription and TE-gene chimera formation in esophageal squamous cell carcinoma (ESCC) remains poorly defined. To address this, we performed a comprehensive transcriptome-wide analysis of TE expression and TE-gene chimeric transcripts in KYSE150 ESCC cells following combined 125I radiation and carfilzomib treatment. The TE analysis showed 148 dysregulated TEs, characterized by ERV1 LTR element enrichment and distinct treatment-control sample separation, indicating structured remodeling of the TE transcriptome. We identified 301 significant TE-gene chimeric events, indicating category-specific remodeling with an increase in TE-initiated and TE-exonic chimeras and a decrease in TE-terminal events. The TE families that underwent the most transcriptional changes were not those that drove chimeric events, indicating that global TE activation does not passively cause chimera remodeling. The gene repression was strongly associated with chimeric transcripts, and gene expression changes were negatively correlated with chimerism frequency. SPANXN1, IL1RL1, and RSAD2, strongly downregulated genes, produced novel TE-derived isoforms and were high-potential functional candidates. Epigenetic context analysis showed considerable overlap between exonized chimeras and candidate cis-regulatory elements, suggesting a potential association with regulatory genomic contexts. Pathway enrichment analysis showed synchronized transcriptomic reprogramming and cell cycle and DNA repair pathway activation and autophagy inhibition. In esophageal cancer cells, concurrent genotoxic and proteotoxic stress causes complex TE remodeling, linking traditional TE transcriptional alterations to structured TE-gene chimera development and stress-related transcriptome reprogramming.
Majid et al. (2026) studied this question.