Enhanced radiation response in radioresistant MCF-7 cells by targeting peroxiredoxin II

In our previous study, we identified that a protein target, peroxiredoxin II (PrxII), is overexpressed in radioresistant MCF+FIR3 breast-cancer cells and found that its expression and function is associated with breast-cancer radiation sensitivity or resistance. Small interference RNA (siRNA) targeting PrxII gene expression was able to sensitize MCF+FIR3 radioresistant breast-cancer cells to ionizing radiation. The major focus of this work was to investigate how the radiation response of MCF+FIR3 radioresistant cells was affected by the siRNA that inhibits PrxII gene expression. Our results, presented here, show that silencing PrxII gene expression increased cellular toxicity by altering cellular thiol status, inhibiting Ca²⁺ efflux from the cells, and perturbing the intracellular Ca²⁺ homeostasis. By combining radiotherapy and siRNA technology, we hope to develop new therapeutic strategies that may have potential to enhance the efficacy of chemotherapeutic agents due to this technology's property of targeting to specific cancer-related genes.