Effect of siRNA-promoted Silencing of Prion Protein on Doxorubicin-induced Cell Death Machineries in Human Adriamycin-resistant Small Cell Lung Cancer Cell Line H69AR

Abstract Background Multidrug resistance is one of major challenges in cancer therapy. Recent data have proposed that among its many cellular functions, prion protein (PrP) is also involved in the acquisition of a multidrug resistance phenotype of cancer cells. In this study, we examined the effect of PrP on doxorubicin-induced cell death in the human adriamycin-resistant small cell lung cancer cell line H69AR. Methods We established an experimental design with a series of groups including knockdown of PrP expression in H69AR cells by siRNA (siRNA group), doxorubicin treatment at IC50 concentration (Doxo IC50 group) and combination of siRNA transfection/doxorubicin IC50 treatment (siRNA/Doxo IC50 group). qRT-PCR and immunocytochemistry analyses were performed for PrP, CD44, Bax and Beclin-1 expressions. Results siRNA transfection and co-delivery of siRNA transfection/doxorubicin treatment decreased the PrP mRNA expression and immunofluorescence signals for PrP. However, doxorubicin treatment at IC50 concentration increased the PrP levels. Besides, the increased expression of CD44, Bax and Beclin-1 proteins was observed in all three groups. Monodansylcadaverine results indicated that the number of autophagic vacuoles was increased in all the experimental conditions. Conclusions Our results suggest that knockdown of PrP in H69AR cells may ameliorate the doxorubicin-induced cell death machineries such as apoptosis and autophagy. In conclusion, the knockdown of PrP may be an attractive strategy for the treatment of drug-resistant cancers to improve the effect of conventional chemotherapeutics.