Abstract
            Background: Drug resistance due to genetic variations renders many therapeutic methods such as  surgery, radiotherapy, chemotherapy, and hormone therapy unsuccessful in eradicating cancerous cells.  Nowadays, application of nanoparticles (NPs) has been promising in destroying cancerous cells without  side effects on normal cells. 
   Objectives: This study aimed to investigate the antioxidant and anticancer effects of biosynthesized  cerium oxide nanoparticles (CeO2  -NPs) on a hepatic carcinoma cell line.  
  Methods: MTT assay was used to determine the cytotoxicity of CeO2  -NPs in concentrations of 0, 15.6,  31.2, 62.5, 125, and 250 μg/mL after 24, 48, and 72 hours of incubation. Moreover, the expression levels  of catalase (CAT) and superoxide dismutase (SOD) (the antioxidant genes) were investigated at different  concentrations of CeO2  -NPs using real-time polymerase chain reaction (PCR). 
   Results: Our results showed a significant toxicity of the synthesized NPs against the cancerous liver cells.  The IC50 calculated for CeO2  -NPs was 500 μg/mL at 24 hours of incubation. In addition, the expression  levels of CAT and SOD significantly (P<0.05) increased upon the treatment of cells with CeO2  -NPs (500  µg /mL) compared to the untreated cells. 
   Conclusion: Considering the minimal effects of the biosynthesized CeO2  -NPs on normal cells and on  the other hand their considerable toxicity against hepatic cancer cells, these NPs could be utilized in  medicine and in the development of new drugs for cancer cells.