title: Shikonin induces cell cycle arrest in human gastric cancer (AGS) by early growth response 1 (Egr1)-mediated p21 gene expression.
abstract: BACKGROUND
  Lithospermum erythrorhizon, a naphthoquinone compound derived from a shikonin, has long been used as traditional Chinese medicine for treatment of various diseases, including cancer. To evaluate the cytotoxic effects of shikonin on AGS gastric cancer cells via induction of cell cycle arrest.
  
  
  METHODS
  We observed the effects of 12.5-100 ng/mL dosage of shikonin treatment on AGS cancer cell line with the incubation time of 6h. Cytotoxic effects were assessed by measuring the changes in the intracellular ROS, appearance of senescence phenotype, cell cycle progression, CDK and cyclins expression levels upon shikonin treatment. We also examined upon the activation of Egr1-mediated p21 expression, by siRNA transfection, Luciferase assay, and ChIP assay.
  
  
  RESULTS
  In this study, we found that shikonin inhibits cell proliferation by arresting cell cycle progression at the G2/M phase via modulation of p21 in AGS cells. Also, our results revealed that the p21 gene was transactivated by early growth response1 (Egr1) in response to the shikonin treatment. Transient Egr1 expression enhanced shikonin-induced p21 promoter activity, whereas the suppression of Egr1 expression by small interfering RNA attenuated the ability of shikonin to induce p21 promoter activity.
  
  
  CONCLUSIONS
  Our results suggested that the anti-proliferative activity of shikonin was due to its ability to induce cell cycle arrest via Egr1-p21 signaling pathway. Thus, the work stated here validates the traditional use of shikonin in the treatment of cancer.
authors.affiliation: College of Life Sciences & Biotechnology, Korea University, 5-1 Anam-dong, Seongbuk-gu, Seoul 136-701, Republic of Korea; Department of Molecular & Cellular Oncology, MD Anderson Cancer Center, 1515 Holcombe Blvd Unit 108, Houston, TX, USA.
authors.forename: Sun-Joong
authors.initials: SJ
authors.lastname: Kim
authors.affiliation: College of Life Sciences & Biotechnology, Korea University, 5-1 Anam-dong, Seongbuk-gu, Seoul 136-701, Republic of Korea.
authors.forename: Jee Min
authors.initials: JM
authors.lastname: Kim
authors.affiliation: Department of Microbiology, College of Medicine, Korea University, 5-1 Anam-dong, Seongbuk-gu, Seoul 136-701, Republic of Korea.
authors.forename: So Hee
authors.initials: SH
authors.lastname: Shim
authors.affiliation: College of Life Sciences & Biotechnology, Korea University, 5-1 Anam-dong, Seongbuk-gu, Seoul 136-701, Republic of Korea. Electronic address: hichang@korea.ac.kr.
authors.forename: Hyo Ihl
authors.initials: HI
authors.lastname: Chang
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D059447:Cell Cycle Checkpoints / Q000187:drug effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000235:genetics*; D051766:Early Growth Response Protein 1 / Q000235:genetics*; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D006801:Humans; D009285:Naphthoquinones / Q000494:pharmacology*; D034741:RNA, Small Interfering / Q000235:genetics; D013274:Stomach Neoplasms / Q000235:genetics*
chemical_list: D000970:Antineoplastic Agents; C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; C497325:EGR1 protein, human; D051766:Early Growth Response Protein 1; D009285:Naphthoquinones; D034741:RNA, Small Interfering; C016101:shikonin
keywords: Anti-proliferation; CDK; CKI; Cell cycle arrest; ChIP; Egr1; Shikonin; chromatin immunoprecitiation; cyclin dependent kinase; cyclin-dependent kinase; early growth response 1; p21; siRNA; small interfering RNA