Comprehensive analysis of DNA repair, morphological remodeling and immune-gene expression in patient-derived biliary tract carcinoma organoids following ionizing radiation.

Biliary tract carcinoma (BTC) is a malignancy with poor prognosis. Current molecular targeted therapies benefit only a limited subset of patients, underscoring the need for novel approaches, such as combining DNA-damaging chemoradiotherapy with an immune checkpoint inhibitor. Although cellular responses following chemoradiotherapy-induced DNA damage are essential, they remain poorly understood in the context of three-dimensional tumor structures. This study aimed to investigate the effects of ionizing radiation, a DNA-damaging cancer therapy, on patient-derived BTC organoids. DNA repair and gene expression regulation was integrally examined by immunofluorescence and RNA-Seq analysis following 10 Gy of X-rays. X-ray irradiation caused significant morphological changes. In addition, X-ray irradiation upregulated extracellular matrix-related gene expression as revealed by RNA sequencing. DNA damage response analysis indicated that non-homologous end joining was the primary repair pathway in patient-derived BTC organoids. Moreover, X-ray irradiation activated immune-related pathways, such as cGAS/STING, RIG-I/MDA-5, and JAK/STAT, suggesting potential immune activation following radiotherapy. Our study revealed that DNA damage response altered the tumor structure and modulated the expression of multiple genes, including extracellular matrix- and immune-related genes. Studies using in vitro organoid models can be useful for investigating three-dimensional cellular responses after DNA-damaging cancer therapies, such as chemoradiotherapy.