Pro-oxidant drugs have been proposed for treating certain cancers but the resistance developed by cancer cells to oxidative stress limits its potential use in clinics. To understand the mechanisms underlying resistance to oxidative stress, we found that the chronic exposure to an H2O2-generating system (ascorbate/menadione, Asc/Men) or catalase overexpression (CAT3 cells) increased the resistance of cancer cells to oxidative stress, likely by increasing the antioxidant status of cancer cells.
Modulation of catalase expression was performed by either protein overexpression or protein down-regulation using siRNA against catalase and aminotriazole as pharmacological inhibitor. The former approach was done by transfecting cells with a plasmid construct containing human catalase cDNA (CAT3 cells, derived from MCF-7 breast cancer cell line) or by generating resistant cells through chronic exposure to an oxidant injury (Resox cells). Cell survival was monitored by using the MTT reduction assay and further calculation of IC50 values. Protein expression was done by Western blots procedures. The formation of reactive oxygen species was performed by flow cytometry. The transcriptional activity of human catalase promoter was assessed by using transfected cells with a plasmid containing the − 1518/+ 16 promoter domain.
Using Resox and CAT3 cells (derived from MCF-7 breast cancer cell line) as models for cancer resistance to pro-oxidative treatment, we found that arsenic trioxide (ATO) remarkably sensitized Resox and CAT3 cells to Asc/Men treatment. Since catalase is a key antioxidant enzyme involved in detoxifying Asc/Men (as shown by siRNA-mediated catalase knockdown) that is overexpressed in resistant cells, we hypothesized that ATO might regulate the expression levels of catalase. Consistently, catalase protein level is decreased in Resox cells when incubated with ATO likely by a decreased transcriptional activity of the catalase promoter.
Our findings support the proposal that ATO should be administered in combination with pro-oxidant drugs to enhance cancer cell death in solid tumors.
Iland HJ, Bradstock K, Supple SG, Catalano A, Collins M, Hertzberg M, et al. Lymphoma, All-trans-retinoic acid, idarubicin, and IV arsenic trioxide as initial therapy in acute promyelocytic leukemia (APML4). Blood. 2012;2012(120):1570–80. CrossRef
Shen ZX, Chen GQ, Ni JH, Li XS, Xiong SM, Qiu QY, et al. Use of arsenic trioxide (As2O3) in the treatment of acute promyelocytic leukemia (APL): II. Clinical efficacy and pharmacokinetics in relapsed patients. Blood. 1997;89:3354–60. PubMed
Varghese MV, Manju A, Abhilash M, Paul MV, Abhilash S, Nair RH. Oxidative stress induced by the chemotherapeutic agent arsenic trioxide. 3. Biotech. 2014;4:425–30.
Verrax J, Vanbever S, Stockis J, Taper H, Calderon PB. Role of glycolysis inhibition and poly(ADP-ribose) polymerase activation in necrotic-like cell death caused by ascorbate/menadione-induced oxidative stress in K562 human chronic myelogenous leukemic cells. Int J Cancer. 2007;120:1192–7. CrossRefPubMed
Nenoi M, Ichimura S, Mita K, Yukawa O, Cartwright IL. Regulation of the catalase gene promoter by Sp1, CCAAT-recognizing factors, and a WT1/Egr-related factor in hydrogen peroxide-resistant HP100 cells. Cancer Res. 2001;61:5885–94. PubMed
- Catalase down-regulation in cancer cells exposed to arsenic trioxide is involved in their increased sensitivity to a pro-oxidant treatment
Pedro Buc Calderon
- BioMed Central
Neu im Fachgebiet Onkologie
Mail Icon II