Dose dependent expression of extracellular microRNAs in HCT116 colorectal cancer cells exposed to high dose rate ionizing radiation

Biomarkers of tumour response to radiotherapy could help in optimising cancer treatment. In this study, we focus on identifying changes in extracellular miRNA as a biomarker of radiation-induced damage to human colorectal cancer cells. HCT116 cells were exposed to increasing doses of X-rays, and extracellular miRNAs were analysed by microarray. The results were correlated with frequencies of micronuclei. Fifty-nine miRNAs with positive correlation and four with negative correlation between dose (up to 6 Gy) and expression of extracellular miRNA were verified. In addition, for samples between 0 and 10 Gy, 12 miRNAs into those 59 miRNAs with positive correlation were verified. Of these, these miRNAs showed significantly positive correlation up to 10 Gy between micronucleus frequency and expression of extracellular miRNA. These results suggest that specific miRNAs could be cell damage markers and could serve as secreted radiotherapy response biomarkers for colorectal cancer; however, the results must be validated in serum samples collected from patients undergoing radiotherapy. Radiation induced extracellular micro RNA expression in murine colon cancer cell (HCT116) was measured at 72 hours after exposure to doses of 0, 6 and 10 Gy X-rays. Four independent experiments were performed at each doses using different cell culture.