title: Inhibition of janus kinase 2 by compound AG490 suppresses the proliferation of MDA-MB-231 cells via up-regulating SARI (suppressor of AP-1, regulated by IFN).
abstract: OBJECTIVE
  The Janus kinase-signal transducers and activators of transcription signaling pathway (JAK/STAT pathway) play an important role in proliferation of breast cancer cells. Previous data showed that inhibition of STAT3 suppresses the growth of breast cancer cells, but the associated mechanisms are not well understood. This study aims to investigate the effect and associated mechanisms of JAK/STAT pathway inhibitor AG490 on proliferation and suppression of breast cancer cells.
  
  
  METHODS
  CCK-8 assay and trypan blue exclusion assay were used to investigate the cytotoxicity of AG490 to MDA-MB-231 cells. Real-time PCR was used to detect the mRNA level of SARI (suppressor of AP-1, regulated by IFN). Western blot was used to analyze the protein levels of SARI, phospho-STAT3 and total STAT3. Luciferase reporter assay was adopted to explore the mechanism of SARI mRNA upregulation.
  
  
  RESULTS
  AG490 suppressed the proliferation of MDA-MB-231 cells in a dose-dependent manner. AG490 significantly up-regulated the mRNA and protein levels of SARI in MDA-MB-231 cells. Knockdown of SARI obviously attenuated AG490-induced growth suppression effect in MDA-MB-231 cells. Furthermore, AG490 dramatically enhanced the transcription activity of SARI promoter. But the transcription activity of truncated SARI promoter, which does not contain STAT3 binding site, cannot be activated by AG490 treatment.
  
  
  CONCLUSIONS
  We demonstrate in this study that AG490 suppresses the proliferation of MDA-MB-231 cells through transcriptional activation of SARI.
authors.affiliation: Department of Radiation Oncology, Shandong Cancer Hospital, Shandong University, Jinan, Shandong, China ; Department of Radiation Oncology, Linyi People's Hospital, Linyi, Shandong, China.
authors.forename: Yan-Xia
authors.initials: YX
authors.lastname: Zhang
authors.affiliation: Department of Radiation Oncology, Linyi People's Hospital, Linyi, Shandong, China.
authors.forename: Li
authors.initials: L
authors.lastname: Yan
authors.affiliation: Department of Traumatology, Linyi People's Hospital, Linyi, Shandong, China.
authors.forename: Guang-Yu
authors.initials: GY
authors.lastname: Liu
authors.affiliation: Department of Radiation Oncology, Linyi People's Hospital, Linyi, Shandong, China.
authors.forename: Wen-Jun
authors.initials: WJ
authors.lastname: Chen
authors.affiliation: Department of Radiation Oncology, Linyi People's Hospital, Linyi, Shandong, China.
authors.forename: Wei-Hong
authors.initials: WH
authors.lastname: Gong
authors.affiliation: Department of Radiation Oncology, Shandong Cancer Hospital, Shandong University, Jinan, Shandong, China.
authors.forename: Jin-Ming
authors.initials: JM
authors.lastname: Yu
keywords: AG490; MDA-MB-231; Proliferation; SARI; STAT3