Comparative ultrastructure analysis of radiation-induced radioresistant laryngeal cancer hep-2 cell line

Radioresistance is one of the main reasons for the failure of radiotherapy in laryngeal cancer. However, the mechanisms of radioresistance of tumor cells have remained elusive. This study was conducted to identify the ultrastructural changes of radiation-induced radioresistant laryngeal cancer hep-2 cell line. First, a radioresistant hep-2R cell line was generated after prolonged exposure to γ-rays for 60 Gy (6 Gy/day, 2 days/week) and was confirmed by clonogenic assay. Next, the ultrastructural differences between hep-2R cells and hep-2 cells were compared by transmission electron microscopy. Finally, the results showed that hep-2R cells showed significant resistance to radiation compared with parental hep-2 cells. Increased cell nucleus atypia, more rough endoplasmic reticulum and less mitochondria were observed in hep-2R cells. The amount of microvilli of hep-2R was similar to hep-2 cell. In summary, these ultrastructural differences revealed the morphological mechanism that hep-2R cells had stronger radioresistance than hep-2 cells.