Yan-xia Zhang - Department of Radiation Oncology, Shandong Cancer Hospital, Shandong University, Jinan, Shandong, China
Li Yan - Department of Radiation Oncology, Linyi People’s Hospital, Linyi, Shandong, China
Guang-yu Liu - Department of Traumatology, Linyi People’s Hospital, Linyi, Shandong, China
Wen-jun Chen - Department of Radiation Oncology, Linyi People’s Hospital, Linyi, Shandong, China
Wei-hong Gong - Department of Radiation Oncology, Linyi People’s Hospital, Linyi, Shandong, China
Jin-ming Yu - Department of Radiation Oncology, Shandong Cancer Hospital, Shandong University, Jinan, Shandong, China

Objective(s): 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 STAT۳ 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 AG۴۹۰ on proliferation and suppression of breast cancer cells. Materials and Methods: CCK-۸ assay and trypan blue exclusion assay were used to investigate the cytotoxicity of AG۴۹۰ to MDA-MB-۲۳۱ cells. Real-time PCR was used to detect the mRNA level of SARI (suppressor of AP-۱, regulated by IFN). Western blot was used to analyze the protein levels of SARI, phospho-STAT۳ and total STAT۳. Luciferase reporter assay was adopted to explore the mechanism of SARI mRNA upregulation. Results: AG۴۹۰ suppressed the proliferation of MDA-MB-۲۳۱ cells in a dose-dependent manner. AG۴۹۰ significantly up-regulated the mRNA and protein levels of SARI in MDA-MB-۲۳۱ cells. Knockdown of SARI obviously attenuated AG۴۹۰-induced growth suppression effect in MDA-MB-۲۳۱ cells. Furthermore, AG۴۹۰ dramatically enhanced the transcription activity of SARI promoter. But the transcription activity of truncated SARI promoter, which does not contain STAT۳ binding site, cannot be activated by AG۴۹۰ treatment. Conclusion: We demonstrate in this study that AG۴۹۰ suppresses the proliferation of MDA-MB-۲۳۱ cells through transcriptional activation of SARI.

AG۴۹۰, MDA-MB-۲۳۱, Proliferation, SARI, STAT۳