Anti-proliferation Effect Of Sunitinib On Head And Neck Cancer Cells Via Inhibition Of STAT3 Pathway

Objective: Sunitinib,a multi-targeted tyrosine kinase inhibitor,has been widely used in the therapy of a variety of cancers due to its inhibition against the activity of various receptor tyrosine kinases related with angiogenesis and good anti-angiogenic effect.Recent studies have shown that sunitinib induces tumor cell apoptosis rather than depending on its anti-angiogenic effect.STAT3,a member of the signal transduction and activator of transcription(STAT)family,is an important component of multiple tyrosine kinase signaling pathways,and is up regulated in a variety of malignant tumor cells,including head and neck cancers.STAT3 hyperactivation and sustained high expression is closely related with the apoptosis inhibition of these malignant tumors,tumor cell proliferation,tumor microenvironment angiogenesis and metastasis.There are few reports about whether sunitinib induces apoptosis of head and neck cancer cells or STAT3 plays a role in the process so far.In the present study,head and neck cancer cell lines UM-22 B and SCC90 were treated with sunitinib,their proliferation and apoptosis,and changes of STAT1 and STAT3 were investigated,so as to further understand the action and mechanism of sunitinib on head and neck cancers,and provide therorical evidence for the clinical treatment with sunitinib on head and neck cancers.Methods: SCC90 and UM-22 B cells were cultured in vitro.Cell proliferation inhibition was tested with MTT assay,inverted microscope observation and other methods respectively after the cells were treated with sunitinib at different concentrations for indicated time periods.STAT1 and STAT3 phosphorylation levels were measured with flow cytometry.Results: 1 Effect of sunitinib on proliferation of two cell lines: MTT results showed that the inhibitory rate of sunitinib on proliferation of SCC90 cells was up to 92.89%;IC50 was 2.37,1.17 and 0.93μmol/L at 24,48 and 72 h,respectively.The inhibition rate on UM-22 B cells was up to 82.56%;IC50 was 6.30 and 2.31μmol/L at 24 and 48 h,respectively.The growth inhibition rates were significantly different with treatment concentration and duration,and the rate is apparently in a time-concentration dependent manner;2 Morphological changes: Under inverted microscope,all of SCC90 and UM-22 B cells displayed as followed: the adherent cells in the control group grew rapidly in a paving stone pattern and flattened and polygon shape.The round nucleus was near the center of plump cytoplasm.The cell growth in the treatment group was significantly inhibited,and the adherent cells were smaller and rounded,the conjection loosed and the nuclear color deepened;3 Effect of sunitinib on STAT1 and STAT3 phosphorylation levels: The positive expression of p-STAT1 in each experiment group was not statistically different from that in the control group after SCC90 cells were treated with 0.25,0.5 and 1 μmol/L sunitinib for 2,8,16 and 24 h respectively.While the positive expression of p-STAT3 was significantly lower than that of the control group.Its positive rate decreased significantly with increased concentration and the difference was statistically significant.The positive expression of p-STAT3 in each experiment group was lower than that in the control group and the positive rate decreased significantly with increased concentration after UM-22 B cells were treated with 0.5,1,2 and 4 μmol/L sunitinib for 30 min and 2h respectively.There was no significant difference between 0.5 and 1 μmol/L groups and their corresponding control groups,while significant difference was found between 2 and 4μmol/L groups and their corresponding control groups.Conclusions:1 Sunitinib inhibits the proliferation of head and neck squamous cell carcinoma cells SCC90 and UM-22 B.2 Sunitinib down-regulates the phosphorylation of STAT3 in UM-22 B and SCC90 cells.3 The expression of phosphorylation of STAT1 in the process of sunitinib inhibiting tumor cell proliferation doesn’t be up-regulated..