Head and neck squamous cell carcinoma (HNSCC) is characterized by aggressive local-regional invasion and cervical lymph node metastasis. Src is a tyrosine kinase that frequently demonstrates elevated activity, contributing to increased invasiveness in HNSCC. AZD0530 is a tyrosine kinase inhibitor that displays dual specificity for Src and Abl kinases, and is currently in Phase II trials. In this study we have examined the impact of AZD0530 on invasion-related cytoskeletal Src substrates and on HNSCC invasion. We demonstrate that AZD0530 at concentrations ranging from 0.01 μM to 10 μM inhibits growth of the HNSCC cell lines 1483, HN31, and UMSCC19 as determined by MTT assays. AZD0530 treatment of these lines resulted in diminished tyrosine phosphorylation of Src substrates known to be involved in tumor cell invasion, including cortactin (Y421), p130 CAS (Y165), FAK (Y861) and paxillin (Y31). In accordance with the effects on Src cytoskeletal substrates, AZD0530 at a concentration of 0.1 μM inhibits HNSCC motility and invasion in transwell assays. HNSCC invasion is mediated in part by the formation of invadopodia, protrusions arising from the ventral cell surface that focally degrade extracellular matrix. We assayed the ability of AZD0530 to inhibit invadopodia formation by the use of a model system utilizing Src-deficient (SYF) fibroblasts containing a reintroduced GFP-tagged temperature-sensitive v-Src mutant (tsLA29-GFP). Treatment of these cells with AZD0530 at the permissive temperature showed inhibition of Src activity determined by Western blot analysis of tyrosine 215, and phosphorylation of cortactin at tyrosine 421. Invadopodia formation was readily evident in SYF cells containing activated tsLA29-GFP at the permissive temperature, but was completely abolished with AZD0530 pretreatment. Collectively these data demonstrate that AZD0530 effectively suppresses HNSCC proliferation and motility, with invasion inhibited by the prevention of invadopodia formation. Studies evaluating the anti-invasive effects and targeting of Src substrates by AZD0530 in a mouse model of oral carcinoma are currently ongoing.

98th AACR Annual Meeting-- Apr 14-18, 2007; Los Angeles, CA