title: ESE-1/EGR-1 pathway plays a role in tolfenamic acid-induced apoptosis in colorectal cancer cells.
abstract: Nonsteroidal anti-inflammatory drugs (NSAIDs) are known to prevent colorectal tumorigenesis. Although antitumor effects of NSAIDs are mainly due to inhibition of cyclooxygenase activity, there is increasing evidence that cyclooxygenase-independent mechanisms may also play an important role. The early growth response-1 (EGR-1) gene is a member of the immediate-early gene family and has been identified as a tumor suppressor gene. Tolfenamic acid is a NSAID that exhibits anticancer activity in a pancreatic cancer model. In the present study, we investigated the anticancer activity of tolfenamic acid in human colorectal cancer cells. Tolfenamic acid treatment inhibited cell growth and induced apoptosis as measured by caspase activity and bioelectric impedance. Tolfenamic acid induced EGR-1 expression at the transcription level, and analysis of the EGR-1 promoter showed that a putative ETS-binding site, located at -400 and -394 bp, was required for activation by tolfenamic acid. The electrophoretic mobility shift assay and chromatin immunoprecipitation assay confirmed that this sequence specifically bound to the ETS family protein epithelial-specific ETS-1 (ESE-1) transcription factor. Tolfenamic acid also facilitated translocation of endogenous and exogenous ESE-1 to the nucleus in colorectal cancer cells, and gene silencing using ESE-1 small interfering RNA attenuated tolfenamic acid-induced EGR-1 expression and apoptosis. Overexpression of EGR-1 increased apoptosis and decreased bioelectrical impedance, and silencing of endogenous EGR-1 prevented tolfenamic acid-induced apoptosis. These results show that activation of ESE-1 via enhanced nuclear translocation mediates tolfenamic acid-induced EGR-1 expression, which plays a critical role in the activation of apoptosis.
authors.affiliation: Laboratory of Environmental Carcinogenesis, Department of Pathobiology, College of Veterinary Medicine, University of Tennessee, 2407 River Drive, Knoxville, TN 37996-4542, USA.
authors.forename: Seong-Ho
authors.initials: SH
authors.lastname: Lee
authors.forename: Jae Hoon
authors.initials: JH
authors.lastname: Bahn
authors.forename: Chang Kyoung
authors.initials: CK
authors.lastname: Choi
authors.forename: Nichelle C
authors.initials: NC
authors.lastname: Whitlock
authors.forename: Anthony E
authors.initials: AE
authors.lastname: English
authors.forename: Stephen
authors.initials: S
authors.lastname: Safe
authors.forename: Seung Joon
authors.initials: SJ
authors.lastname: Baek
mesh_terms: D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology; D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis; D001665:Binding Sites; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D015179:Colorectal Neoplasms / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism / Q000502:physiology*; D051766:Early Growth Response Protein 1 / Q000378:metabolism / Q000502:physiology*; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008954:Models, Biological; D011518:Proto-Oncogene Proteins / Q000378:metabolism / Q000502:physiology*; D050783:Proto-Oncogene Proteins c-ets; D034741:RNA, Small Interfering / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism / Q000502:physiology*; D062367:ortho-Aminobenzoates / Q000494:pharmacology*
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D000970:Antineoplastic Agents; D004268:DNA-Binding Proteins; C497325:EGR1 protein, human; C105529:ELF3 protein, human; D051766:Early Growth Response Protein 1; D011518:Proto-Oncogene Proteins; D050783:Proto-Oncogene Proteins c-ets; D034741:RNA, Small Interfering; D014157:Transcription Factors; D062367:ortho-Aminobenzoates; C009500:tolfenamic acid