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The c-Met receptor and its ligand HGF have been shown to be upregulated in HNSCC tumors. c-Met can also have an activating tyrosine kinase domain mutation in HNSCC. SU11274 is a novel small molecule c-Met inhibitor. We evaluated HNSCC tumor samples from 10 patients by immunohistochemistry for c-Met, activated phospho-c-Met pY1003 and pY1234/1235, and HGF. Total c-Met expression was measured by immunoblot in 7 HNSCC cell lines. More than 75% of HNSCC tumor samples expressed both c-Met and activated phospho-c-Met - with pY1003 expression being more prominent than pY1234/1235. HGF expression was seen consistently primarily with cytoplasmic staining in the tumor. All 7 cell lines tested showed expression of c-Met. 5 HNSCC cell lines were treated with SU11274 (small molecule inhibitor against c-Met) at 2μM & 5μM and signaling pathways were examined using immunoblot analysis with various antibodies. 2 HNSCC cell lines were treated with HGF (40ng/ml & 80ng/ml), SU11274 (5μM), and combinations. Cell numbers were measured by MTT assays at 0h, 24h, 48h, and 72h. p-Tyr immunoblots showed activity of SU11274 resulting in a dose dependant decrease in phosphorylation of a number of proteins. Marked inhibition of c-Met signaling was documented in the presence of SU11274 with decreased levels of phospho-c-Met (both pY1003 & pY1230/1234/1235), phospho-Akt (pT308), phospho-Erk1/2 (pTpY185/187), phospho-p70S6K (pT389), and phospho-SHP2 (pY542) at 2μM and complete abrogation of signaling to baseline levels at 5μM. MTT survival assays showed that both 2 and 5μM of SU11274 lead to decreased cell growth in one of the tested HNSCC cell lines and abrogate HGF induced cell proliferation. c-Met signaling plays an important role in HNSCC growth and signaling. Inhibition of c-Met signaling by SU11274 leads to abrogation of respective signaling pathways and in certain HNSCC cell lines growth inhibition.

[Proc Amer Assoc Cancer Res, Volume 46, 2005]