title: Sulforaphane induction of p21(Cip1) cyclin-dependent kinase inhibitor expression requires p53 and Sp1 transcription factors and is p53-dependent.
abstract: Sulforaphane (SFN) is an important cancer preventive agent derived from cruciferous vegetables. We show that SFN treatment suppresses normal human keratinocyte proliferation via a mechanism that involves increased expression of p21(Cip1). SFN treatment produces a concentration-dependent increase in p21(Cip1) promoter activity via a mechanism that involves stabilization of the p53 protein leading to increased p53 binding to the p21(Cip1) promoter p53 response elements. The proximal p21(Cip1) promoter GC-rich Sp1 factor binding elements are also required, as the SFN-dependent increase is lost when these sites are mutated. SFN treatment increases Sp1 binding to these elements, and the response is enhanced in the presence of exogenous Sp1 and reduced in the presence of ΔN-Sp3. CpG island methylation alters p21(Cip1) promoter activity some systems; however, expression in SFN-treated keratinocytes does not involve changes in proximal promoter methylation. The promoter is minimally methylated, and the methylation level is not altered by SFN treatment. This study indicates that SFN increases p21(Cip1) promoter transcription via a mechanism that involves SFN-dependent stabilization of p53 and increased p53 and Sp1 binding to their respective response elements in the p21(Cip1) promoter. These results are in marked contrast to the mechanisms observed in skin cancer cell lines and suggest that SFN may protect normal keratinocytes from damage while causing cancer cells to undergo apoptosis.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, Maryland 21201, USA.
authors.forename: Yap Ching
authors.initials: YC
authors.lastname: Chew
authors.forename: Gautam
authors.initials: G
authors.lastname: Adhikary
authors.forename: Gerald M
authors.initials: GM
authors.lastname: Wilson
authors.forename: Wen
authors.initials: W
authors.lastname: Xu
authors.forename: Richard L
authors.initials: RL
authors.lastname: Eckert
mesh_terms: D016588:Anticarcinogenic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D045744:Cell Line, Tumor; D018899:CpG Islands / Q000502:physiology; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000096:biosynthesis* / Q000235:genetics; D019175:DNA Methylation / Q000187:drug effects / Q000502:physiology; D005786:Gene Expression Regulation / Q000187:drug effects* / Q000502:physiology; D006801:Humans; D017879:Isothiocyanates; D015603:Keratinocytes / Q000378:metabolism*; D055550:Protein Stability / Q000187:drug effects; D020218:Response Elements / Q000502:physiology; D016329:Sp1 Transcription Factor / Q000235:genetics / Q000378:metabolism*; D013454:Sulfoxides; D013861:Thiocyanates / Q000494:pharmacology*; D014158:Transcription, Genetic / Q000187:drug effects / Q000502:physiology; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*
chemical_list: D016588:Anticarcinogenic Agents; C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D017879:Isothiocyanates; D016329:Sp1 Transcription Factor; D013454:Sulfoxides; C495901:TP53 protein, human; D013861:Thiocyanates; D016159:Tumor Suppressor Protein p53; C016766:sulforaphane