Enhancing the radioresponsiveness of colorectal cancer (CRC) is essential for local control and prognosis. However, consequent damage to surrounding healthy cells can lead to treatment failure. We hypothesized that short‑chain fatty acids (SCFAs) could act as radiosensitizers for cancer cells, allowing the administration of a lower and safer dose of radiation. To test this hypothesis, the responses of three‑dimensional‑cultured organoids, derived from CRC patients, to radiotherapy, as well as the effects of combined radiotherapy with the SCFAs butyrate, propionate and acetate as candidate radiosensitizers, were evaluated via reverse transcription‑quantitative polymerase chain reaction, immunohistochemistry and organoid viability assay. Of the three SCFAs tested, only butyrate suppressed the proliferation of the organoids. Moreover, butyrate significantly enhanced radiation‑induced cell death and enhanced treatment effects compared with administration of radiation alone. The radiation‑butyrate combination reduced the proportion of Ki‑67 (proliferation marker)‑positive cells and decreased the number of S phase cells via FOXO3A. Meanwhile, 3/8 CRC organoids were found to be non‑responsive to butyrate with lower expression levels of FOXO3A compared with the responsive cases. Notably, butyrate did not increase radiation‑induced cell death and improved regeneration capacity after irradiation in normal organoids. These results suggest that butyrate could enhance the efficacy of radiotherapy while protecting the normal mucosa, thus highlighting a potential strategy for minimizing the associated toxicity of radiotherapy.

Patient-derived tumor organoids closely resemble original patient tumors. We conducted this co-clinical trial with treatment-naive rectal cancer patients and matched patient-derived tumor organoids to determine whether a correlation exists between experimental results obtained after irradiation in patients and organoids. Between November 2017 and March 2020, we prospectively enrolled 33 patients who were diagnosed with mid-to-lower rectal adenocarcinoma based on endoscopic biopsy findings. We constructed a prediction model through a machine learning algorithm using clinical and experimental radioresponse data. Our data confirmed that patient-derived tumor organoids closely recapitulated original tumors, both pathophysiologically and genetically. Radiation responses in patients were positively correlated with those in patient-derived tumor organoids. Our machine learning-based prediction model showed excellent performance. In the prediction model for good responders trained using the random forest algorithm, the area under the curve, accuracy, and kappa value were 0.918, 81.5%, and 0.51, respectively. In the prediction model for poor responders, the area under the curve, accuracy, and kappa value were 0.971, 92.1%, and 0.75, respectively. Our patient-derived tumor organoid-based radiosensitivity model could lead to more advanced precision medicine for treating patients with rectal cancer.

Kim MJ, et al. Infect Chemother. 2015 Dec;47(4):231-238. http://dx.doi.org/10.3947/ic.2015.47.4.231

LARC patients were sorted according to their radio-responsiveness and patient-derived organoids were established from the respective cancer tissues. Expression profiles for each group were obtained using RNA-seq. Biological and bioinformatic analysis approaches were used in deciphering genes and pathways that participate in the radio-resistance of LARC. Thirty candidate genes encoding proteins involved in radio-responsiveness–related pathways, including the immune system, DNA repair and cell-cycle control, were identified. Interestingly, one of the candidate genes, cathepsin E (CTSE), exhibited differential methylation at the promoter region that was inversely correlated with the radio-resistance of patient-derived organoids, suggesting that methylation status could contribute to radio-responsiveness. On the basis of these results, we plan to pursue development of a gene chip for diagnosing the radio-responsiveness of LARC patients, with the hope that our efforts will ultimately improve the prognosis of LARC patients.