Abstract B52: Evaluation of role of apoptosis and cell cycle analysis in chemopreventive action of fish oil and celecoxib in the initiation phase of experimental mammary carcinogenesis

Abstract

Abstract Aim: Cyclooxygenase (COX)-2 enzymes plays an important role in the progression and metastasis of cancer. COX −2 inhibition by non steroidal anti inflammatory drugs (NSAID) is a useful approach for cancer prevention but has side effects. On the other hand, n-3 polyunsaturated fatty acids (PUFA) also have a cancer chemopreventive effect mediated by COX-2 inhibition. Therefore, the present study was designed to investigate the chemopreventive effect of combined dosage of n-3 PUFA rich fish oil and celecoxib, a COX-2 inhibitor in the initiation phase of experimental mammary carcinogenesis. Study Design: Female Wistar rats were distributed into six groups: group-1 (vehicle treated), group-2 (DMBA treated), group-3 (20mg/kg body weight celecoxib), group-4 (0.5 ml fish oil), group-5 (20 mg/kg body weight celecoxib+0.5 ml fish oil) and group-6 (20 mg/kg body weight celecoxib+0.5 ml fish oil). The treatment was given for seven days and on 8th day animals in all groups except group 1 and 5 received an oral dose of 15mg of DMBA (7, 12-Dimethylbenz (a) anthracene) and sacrificed after 90 days. Histopathology was done for morphological examination of the tissue specimens. Apoptosis was measured by using M30 cytodeath monoclonal antibody and Caspase-3 activity and cell cycle analysis by propidium iodide (PI) staining was performed in isolated mammary epithelial cells. Results: In the animals treated with DMBA, the mammary tissue showed the features of ductal hyperplasia. Treatment with combination dosages of celecoxib+fish oil+DMBA resulted in a histological profile similar to the normal mammary tissue while obstruction in duct and lobule as well as hyperplastic changes were observed in the mammary tissue of celecoxib or fish oil treated animals. Group 2 animals showed a significant increase in apoptosis with M-30 cytoDEATH and caspase-3 activity. In addition, an increase in cell population in S and G2/M phase with a concomitant decrease in G1 phase cells was observed in carcinogen treated animals. In comparison to DMBA treated animals, a decrease in percentage apoptotic cells was observed in celecoxib or/and fish oil pretreated groups followed by DMBA with the least reduction in combinatorial regimen treated animals. There was no significant difference in the Caspase-3 activity in the DMBA treated animals and celecoxib + fish oil + DMBA treated animals. In the animals treated with combination dosage of celecoxib + fish oil + DMBA, there was a significant increase in apoptosis as compared to animals treated with celecoxib and fish oil alone. The apoptosis in the groups was also significantly increased with respect to control animals (group 1). Conclusion: Though both celecoxib and fish oil showed chemopreventive potential in experimental mammary carcinogenesis, better efficacy was observed with the combinatorial treatment and their synergistic effect may be mediated by the apoptotic pathway. Citation Information: Cancer Prev Res 2010;3(12 Suppl):B52.