Targeting metabolic dependencies to reverse chemoradiotherapy resistance in colorectal cancer.

Neoadjuvant chemoradiotherapy (CRT) constitutes a standard treatment for locally advanced rectal cancer (RC), frequently followed by radical surgical resection. Yet, therapeutic responses vary widely, and intrinsic radioresistance remains a major barrier to cure. To uncover actionable determinants of CRT response, we established a panel of patient-derived colorectal cancer cell lines (PDCLs) followed by integrated phenotypic and functional characterization. We identified metabolic reprogramming as a hallmark of radioresistance and, through orthogonal validation experiments, confirmed elevated glycolytic and mitochondrial ATP production in (chemo)irradiation-resistant PDCLs. The causative relationship of this association and its potential for therapeutic intervention was shown by subsequent drug screening, showing resistance to most of the applied drugs and revealing a critical dependency on the monocarboxylate transporter (MCT1) and the glucose transporter 1 (GLUT1). Metabolism-targeting compounds re-sensitized resistant PDCLs to irradiation; especially inhibition of GLUT1 exhibits a robust radiosensitizing activity across models. Concordantly, GLUT1 expression correlated with poor response to neoadjuvant CRT in our own RC patient cohort and various publicly available patient datasets. Collectively, our study defines metabolic dependency as a key driver of CRT resistance in RC, and reveals glycolysis- and lactate-transport-associated pathway activities as targetable vulnerabilities. These findings provide a mechanistic basis for patient stratification and support the development of metabolism-directed strategies to overcome (chemo)radioresistance in RC.