Anti-tumor effects of combination resveratrol and celecoxib in vitro and in vivo Kisková T.1, Jendželovský R.2, Papčová Z.2, Rendsen E.3, Orendáš P.1, Bojková B.1, Fedoročko P. 2, Thalhammer T.3, Kassayová M. 1 Department of Animal Physiology, 2 Department of Cell Biology, Institute of Biology and Ecology, Faculty of Science, P. J. Šafárik University in Košice, 040 01 Košice, Slovak Republic, 3 Department of Pathophysiology and Allergy Research, Medical University of Vienna, 1090 Vienna, Austria Resveratrol is a naturally occurring polyphenol found in some plants such as red grapes or berries. It has been shown to possess anti-proliferative and proapoptotic effects in a plenty of cancer cell lines. A relative high dose of resveratrol has a suppressive effect on the growth of cancer cells; however, lower concentrations can stimulate the cell growth. In vivo, resveratrol has been shown to suppress the tumor growth via multiple pathways including the COX-2 inhibition. Celecoxib, a selective inhibitor of COX-2 activity, displays the anti-proliferative effects in vitro as well as in vivo. Resveratrol could potentiate the anticancer effects of celecoxib. The combination of resveratrol and celecoxib led to the significant decrease in metabolic activity of MCF-7 cells after 24 h exposure as evaluated by the MTT assay. Combination of both agents increased the percentage of cells with dissipated MMP after 48 h exposure as compared to control group, without any changes in the proportion of Annexin V positive cells. However, long-term administration of resveratrol and celecoxib in a chemically induced mammary carcinogenesis in female Sprague-Dawley rats resulted in the significantly reduced tumor incidence, prolonged latency period and significantly decreased tumour frequency and tumor volume. .MCF-7 cells Resveratrol: 1-100 μM Celecoxib: 1-100 μM metabolic activity test (MTT) mitochondrial membrane potential (MMP) drug synergism   Sprague-Dawley rats Resveratrol: 100 mg/kg body weight per os, 5 times a week for 16 weeks Celecoxib 1.67 g/kg food ad libitum for 16 weeks tumor incidence tumor volume tumor frequency tumor latency  expression of COX-2, NAG-1 M A T E R I L S R E S U L T S Metabolic activity of resveratrol, celecoxib and their combination with changes in MMP in MCF-7 cells. Data are expressed as means ± SD of at least three independent experiments. Significance vs. control is by ***P<0.001, vs. Cele by ▫ P<0.05 and vs. Res by ▪▪▪ P<0.001. Resveratrol and celecoxib have been separately well studied for their role in the inhibition of breast cancer. While resveratrol and celecoxib alone were shown to reduce the metabolic activity of MCF-7 cells in dose and time dependent manner, the combination of both resulted in the significant decrease of metabolic activity in comparison to single substances, followed by the synergic action found after 24 h. However, the combination markedly reduced the tumor incidence, tumor frequency and volume and prolonged latency period in NMU-induced mammary carcinogenesis in female Sprague-Dawley rats. Resveratrol with celecoxib led to the significant inhibition of COX-2 and moderate increase of NAG-1 expression. Resveratrol and celecoxib suppresses the tumor growth more efficiently than the single substances. Therefore such combinations should be further studied, particularly as resveratrol is taken by a great number of patients, many of them on NSAIDs therapy. This warrants further studies on the combination of the dietary supplement with the COX-2 inhibitor celecoxib to create an efficient chemoprotective agent for the clinical praxis. Chemopreventive effects of resveratrol with celecoxib in chemically-induced breast cancer in rats. Values are means ± SEM. Significance vs. NMU is by *P<0.05, vs. Res is by • P<0.05. C O N L U S I Immunohistological staining of COX-2 and NAG-1 proteins (above) and mRNA expression of COX-2 and NAG-1 (below). Data in Graphs are presented as means ± SD. Significance vs. NMU group (P<0.05). Detail view of the protein expression of COX-2 (left) and NAG-1 expression (right) in breast cancerous tissue (Magnification 40x). ACKNOWLEDGEMENTS The project was supported by Pfizer Luxembourg SARL, Slovakia, Research and Development Agency (No. VVCE-0001-07) and Institutional grant of P.J. Šafárik University in Košice ((No. VVGS 14/10-11 and VVGS PF 1/2011/B). The experiment was conducted according to the principles provided in the Law No. 23/2009 of Slovak Republic for the Care and Use of Laboratory Animals.