Janus Kinase Inhibitor AG490 Blocks Stat3 Signal Transduction And Mediate Apoptosis In Cancer Cells

Tumor, especially maligenant tumor, seriously threaten human health. The scientists from different fields have been searching therapic measure for maligenant tumor diseases for decades, but little effect has been received. In the past ten years, with rapid development and intensive reseach in theory and technology of cytobiology and molecular biology, researchers discovered that Stat3(signal transducer and activator of transcription-3) involved in some physiological processes in cell growth, differentiation , proliferation, and survival. It was reported that Stat3 was overactiviated in different kinds of maligenant tumor cells, and regarded as one of oncogenes. Cell apoptosis is distinct from cell necrosis in morph and biochemical character in that cell apoptosis is active cell death, which is controlled by expressions of some genes. Death of tumor cells induced by apoptosis can not cause fervent inflammatory reaction, but act as protective effect on normal tissues and cells by killing tumor cells meanwhile. So, researchers pay close attention to presumption that apoptosis of tumor cells mey been induced by inhibiting expression of oncogenes.[Objective]To investigate feasibility and molecular mechanism of Stat3 signal transduction pathway ,we explored effect of Stat3 signal transduction pathway with AG490 inhibitor on proliferation and apoptosis of tumor cells during treating tumor. [Methods]RT-PCR was performed to detect expressions of Stat3m- RNA in tumor cells of human; MMT was used to explore proliferative state of Hela cells, Smmc7721 cells and spleen cells of mice; generation cycle and apoptosis were determined by using flow cytometer and we also investigated expressions of Stat3,bax and bcl-2 Mrna after Stat3 signal transduction pathway was inhibited by AG490- JAK inhibitor in Hela cell.[Results]1 Stat3 was markly expressed in tumor cell lines of human. RT-PCR assay showed that Stat3 mRNA was expressed in 5of 6 tumor cells, including MCF-7, PC-3m, Smmc7721, BGC823 and Hela cells .2 Expressions of Stat3 mRNA were gradually attenuated with time went on after Stat3 signal transduction pathway was inhibited by AG490 at different timepoints . However, expressions of HMGA1 mRNA were intact following Stat3 signal transduction pathway being inhibited.3 Depressant effect of AG490 on proliferation of Hela cells and smmc7721 cells. Compared with control group, experimental group cell proliferation was obviously decreased4 Flow cytometer assay showed AG490 action Hela cells 72h that the ratio of cells in G1 cycle increased by from 64.06% to 70.12% in G1 cycle, decreased by from 28.93% to 14.39% in S cycle, and the ratio cell apoptosis increased by 0.49% to 3.79%. AG490 action smmc7721 cells 72h that the ratio of cells in G1 cycle increased by from 54.19% to 63.51% in G1 cycle, decreased by from 23.09% to 0.03% in S cycle, and AG490 action smmc7721 cells 48h the ratio cell apoptosis increased by 5.96% to 20.51%.5 Change of expressions for tumor related apoptotic factors mediated by Stat3 signal transduction pathway was determined following AG490 treating in Hela cells and Smmc7721 cells. Expressions of bax mRNA were enhanced and bcl-2 mRNA were attenuated, even eliminated after Stat3 signal transduction pathway was blocked in Hela cells; Expressions of bcl-2 mRNA were decreased after Stat3 signal transduction pathway was blocked on Smmc7721 cells.[Conclusions]1 Stat3 mRNA was generally expressed in tumor cells of human.2 Expressions of Stat3 mRNA were downregulated with time went on after tumor cells were treated with AG490.3 Cell proliferation was markly inhibited in tumor cells HeLa and smmc7721, and cell apoptosis was promoted with AG490 treatment at dose of 65μmol/L .4 Expressions of bcl-2 were downregulated, while bax mRNA were upregulated after Stat3 signal transduction pathway was blocked with AG490, JAK inhibitor.To sum up, Stat3 was generally expressed in tumor cells of human, and AG490, one of JAK inhibitors, effectively blocked Stat3 signal transduction pathway, which promoted cell apoptosis through inhibiting cell proliferation . The present study shows that expressions of tumor related apoptotic factors, including bcl-2,bax, are controlled by Stat3 signal transduction pathway. Apoptosis of tumor cells maybe occur following Stat3 signal transduction pathway being blocked, which will lay experimental foundation on treating tumor diseases.