Targeting Eg5 with K858: A Strategy for Radiosensitization Through ROS-Mediated DNA Damage in Esophageal Squamous...

Radiotherapy resistance poses a major challenge in the treatment of esophageal squamous cell carcinoma (ESCC). The kinesin Eg5 is overexpressed in human cancers and has emerged as a candidate therapeutic target. The Eg5 inhibitor K858 cooperates with radiotherapy to block ESCC progression, but whether this synergy stems from modulation of irradiation-induced reactive oxygen species (ROS) and DNA damage is unknown. We aimed to establish the clinical significance of Eg5 in ESCC, and to investigate whether pharmacological Eg5 inhibition by K858 enhances radiosensitivity via ROS-mediated DNA damage.

We employed bioinformatic interrogation of public databases, retrospective analysis of an institutional patient cohort (n = 30) with immunohistochemistry validation, and in vitro studies using ESCC cell lines. We assessed correlations between Eg5 expression levels, clinicopathological features, and patient survival. ROS generation was measured by flow cytometry, and γH2AX foci detection by immunofluorescence following K858 and radiotherapy treatment.

Eg5 mRNA and protein levels were highly upregulated across ESCC and various cancers compared to normal tissues. Eg5 expression correlated with smoking history, poorer histological grade, and reduced overall survival in our patient cohort. Furthermore, a negative correlation between Eg5 expression and E-cadherin status identified Eg5 as a regulator of epithelial-mesenchymal transition. Mechanistically, K858 treatment enhanced ROS generation and increased γH2AX foci accumulation induced by radiotherapy, indicating that inhibition of Eg5 promotes radiotherapy efficacy through oxidative DNA injury.

These data support the combination of K858, an Eg5-targeting compound, and radiotherapy as a strategy for treating ESCC by enhancing oxidative stress and unresolved DNA lesions. Our results suggest that kinesin Eg5 may be utilized not only as a prognostic biomarker but also as a bona fide target for overcoming radioresistance.

Eg5 represents not only an independent prognostic marker but also a promising drug target for ESCC, yet the findings still need to be validated in large-scale prospective studies. Inhibiting this kinesin protein with K858 may represent a novel therapeutic strategy to sensitize ESCC to radiotherapy.