Cyclooxygenase‐2 overexpression in MCF‐10F human breast epithelial cells inhibits proliferation, apoptosis and differentiation, and causes partial transformation

Abstract

To investigate the effects of cyclooxygenase-2 (COX-2) overexpression on breast cancer development, we stably transfected MCF-10F human breast epithelial cells with an expression vector containing human COX-2 cDNA oriented in the sense (10F-S) or antisense (10F-AS) direction. As expected, 10F-S cells expressed elevated levels of COX-2 protein, whereas this protein was undetectable in the 10F-AS cells. Prostaglandin E 2 production in these cells reflected COX-2 levels. The 10F-S cells had a significantly decreased rate of proliferation compared to 10F-AS or parental cells, and a delay in progression through the G 1 phase of the cell cycle. COX-2 overexpression also caused resistance to detachment-induced apoptosis (anoikis) as well as an inhibition of differentiation in cells cultured in Matrigel. Furthermore, after 20 passages in culture, 10F-S cells developed fibroblast-like features, expressed vimentin, and formed foci of dense growth when cultured at confluence, suggesting that the cells were undergoing epithelial to mesenchymal transition (EMT). The 10F-S cells, however, were unable to grow in soft agar or form tumors in nude mice, suggesting that they were only partially transformed. Our observations suggest that COX-2 overexpression in human breast epithelial cells will predispose the mammary gland to carcinogenesis. ' 2005 Wiley-Liss, Inc.Key words: cyclooxygenase-2; human breast epithelial cells; cell proliferation; apoptosis; differentiation Cyclooxygenase (COX) is the rate-limiting enzyme in the biosynthesis of eicosanoids from arachidonic acid. There are 2 COX isoforms: the constitutive form, COX-1, is involved in processes such as parturition and platelet aggregation; 1 the inducible form, COX-2, is involved in inflammatory reactions 1 as well as ovulation, implantation, perinatal renal development and remodeling of the ductus arteriosus. 2 COX-2 expression is induced by a variety of proinflammatory agents, growth factors, tumor promoters and mitogens. 1,3 Nonsteroidal anti-inflammatory drugs (NSAIDs) inhibit either COX-1, COX-2 or both isoforms, depending on the structure of the drug, and are widely used for the treatment of rheumatoid-and osteo-arthritis.Recently, overexpression of COX-2 has been found to be a general feature of neoplasms, particularly those of epithelial origin, in both experimental animals and humans. In humans, upregulation of COX-2 has been reported for colon cancers associated with familial adenomatous polyposis, as well as sporadic colorectal cancer, and for cancers of the stomach, lung, esophagus, liver, bile duct, pancreas and skin. 4 NSAIDs have been shown to inhibit the development and/or growth of a variety of carcinomas in experimental animals including colon, 5 skin 6 and lung. 7 A number of lines of evidence have linked COX-2 to the development of breast cancer. Approximately 50% of human breast tumors express COX-2 8,9 and recent epidemiological studies have suggested an inverse association between regular use of NSAIDs and the risk of breast cancer. 10,11 We and oth...

Cyclooxygenase-2 Expression Induces Genomic Instability in MCF10A Breast Epithelial Cells

“…Similar to our result showing inhibition of anoikis upon COX-2 expression in MCF10A cells, others have reported inhibition of anoikis upon COX-2 overexpression in another breast cancer cell line, MCF10F [24]; however, that study did not include analysis of genomic instability. In support of our model regarding the role of AKT in MCF10A/COX-2 cells, COX-2 expression also inhibits anoikis in bladder cancer cells in a PI3K/AKT dependent manner [22].…”

Cyclooxygenase-2 Inhibits UVB-Induced Apoptosis in Mouse Skin by Activating the Prostaglandin E2 Receptors, EP2 and EP4

“…Although studies have shown that COX-2 induction/expression can inhibit apoptosis (10,31,32), and that COX-2 inhibition can increase apoptosis (11,33,34), little is known about the effects of the mechanism of COX-2. In the present study, using an in vivo model, we investigated the involvement of the PGE 2 receptors in UVB-induced apoptosis and show that epidermal apoptosis in COX-2À/À mice is mitigated by EP2 and EP4 agonists.…”

A JNK1/AP-1–Dependent, COX-2 Induction Is Implicated in 12-O-Tetradecanoylphorbol-13-Acetate–Induced Cell Transformation through Regulating Cell Cycle Progression

“…Although the implications of COX-2 in cell proliferation, cell transformation, and carcinogenesis have been evidential in most of the previous studies (4,20), there is still some evidence showing that COX is not involved in biological effects in some systems (38,39). For example, Lu et al (38) has reported that overexpressing human cDNA of COX-2 in human breast epithelial cells inhibited cell proliferation by delaying cell cycle progression through the G 1 phase.…”

“…Although the implications of COX-2 in cell proliferation, cell transformation, and carcinogenesis have been evidential in most of the previous studies (4,20), there is still some evidence showing that COX is not involved in biological effects in some systems (38,39). For example, Lu et al (38) has reported that overexpressing human cDNA of COX-2 in human breast epithelial cells inhibited cell proliferation by delaying cell cycle progression through the G 1 phase. Our recent findings show that reducing epidermal growth factor -induced COX-2 expression by knockdown transcription factor NFAT3 had no inhibitory effect on the epidermal growth factor -induced cell transformation, indicating that COX-2 induction by epidermal growth factor has no direct relevance to cell transformation (39).…”