title: Curcumin and synthetic analogs induce reactive oxygen species and decreases specificity protein (Sp) transcription factors by targeting microRNAs.
abstract: BACKGROUND
  Curcumin inhibits growth of several cancer cell lines, and studies in this laboratory in bladder and pancreatic cancer cells show that curcumin downregulates specificity protein (Sp) transcription factors Sp1, Sp3 and Sp4 and pro-oncogenic Sp-regulated genes. In this study, we investigated the anticancer activity of curcumin and several synthetic cyclohexanone and piperidine analogs in colon cancer cells.
  
  
  METHODS
  The effects of curcumin and synthetic analogs on colon cancer cell proliferation and apoptosis were determined using standardized assays. The changes in Sp proteins and Sp-regulated gene products were analysed by western blots, and real time PCR was used to determine microRNA-27a (miR-27a), miR-20a, miR-17-5p and ZBTB10 and ZBTB4 mRNA expression.
  
  
  RESULTS
  The IC50 (half-maximal) values for growth inhibition (24 hr) of colon cancer cells by curcumin and synthetic cyclohexanone and piperidine analogs of curcumin varied from 10 μM for curcumin to 0.7 μM for the most active synthetic piperidine analog RL197, which was used along with curcumin as model agents in this study. Curcumin and RL197 inhibited RKO and SW480 colon cancer cell growth and induced apoptosis, and this was accompanied by downregulation of specificity protein (Sp) transcription factors Sp1, Sp3 and Sp4 and Sp-regulated genes including the epidermal growth factor receptor (EGFR), hepatocyte growth factor receptor (c-MET), survivin, bcl-2, cyclin D1 and NFκB (p65 and p50). Curcumin and RL197 also induced reactive oxygen species (ROS), and cotreatment with the antioxidant glutathione significantly attenuated curcumin- and RL197-induced growth inhibition and downregulation of Sp1, Sp3, Sp4 and Sp-regulated genes. The mechanism of curcumin-/RL197-induced repression of Sp transcription factors was ROS-dependent and due to induction of the Sp repressors ZBTB10 and ZBTB4 and downregulation of microRNAs (miR)-27a, miR-20a and miR-17-5p that regulate these repressors.
  
  
  CONCLUSIONS
  These results identify a new and highly potent curcumin derivative and demonstrate that in cells where curcumin and RL197 induce ROS, an important underlying mechanism of action involves perturbation of miR-ZBTB10/ZBTB4, resulting in the induction of these repressors which downregulate Sp transcription factors and Sp-regulated genes.
authors.affiliation: College of Medicine, Texas A&M Health Science Center, Houston, TX 77030, USA.
authors.forename: Shruti U
authors.initials: SU
authors.lastname: Gandhy
authors.forename: Kyounghyun
authors.initials: K
authors.lastname: Kim
authors.forename: Lesley
authors.initials: L
authors.lastname: Larsen
authors.forename: Rhonda J
authors.initials: RJ
authors.lastname: Rosengren
authors.forename: Stephen
authors.initials: S
authors.lastname: Safe
mesh_terms: D017209:Apoptosis / Q000187:drug effects / Q000235:genetics; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D003110:Colonic Neoplasms / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism; D003474:Curcumin / Q000031:analogs & derivatives* / Q000494:pharmacology*; D019938:Cyclin D1 / Q000235:genetics / Q000378:metabolism; D003512:Cyclohexanones / Q000494:pharmacology; D015536:Down-Regulation / Q000187:drug effects; D066246:ErbB Receptors / Q000235:genetics / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D035683:MicroRNAs / Q000235:genetics*; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism; D010880:Piperidines / Q000494:pharmacology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism; D019859:Proto-Oncogene Proteins c-met / Q000235:genetics / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism*; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D051703:Sp Transcription Factors / Q000235:genetics* / Q000378:metabolism*
chemical_list: D003512:Cyclohexanones; D035683:MicroRNAs; D016328:NF-kappa B; D010880:Piperidines; D019253:Proto-Oncogene Proteins c-bcl-2; D017382:Reactive Oxygen Species; D012097:Repressor Proteins; D051703:Sp Transcription Factors; C559929:ZBTB10 protein, human; C508974:ZBTB4 protein, human; D019938:Cyclin D1; C036468:cyclohexanone; C032727:piperidine; C512478:EGFR protein, human; D066246:ErbB Receptors; C491743:MET protein, human; D019859:Proto-Oncogene Proteins c-met; D003474:Curcumin