Effects of the Src inhibitor AZD0530 on the cellular response to radiation treatment in vitro

Background: Metastasis is the primary cause of cancer mortality. Metastasis associates with cell changes including increased motility, altered adhesion and increased invasive potential. The non-receptor tyrosine kinase Src plays a key role in many of these processes and so may be exploited as a therapeutic target. Radiotherapy has been associated with acquired metastatic characteristics so this treatment in combination with Src inhibition was evaluated.Methods: The effects of the Src inhibitor AZD0530 in combination with radiation were evaluated on a panel of cell lines. The anti-adhesive, migratory and invasive effects were assessed in vitro using well-characterised motility and adhesion assays as well as immunofluorescence to visualise focal adhesions. The effect on cell survival was demonstrated using colony forming assays. Results: Radiation (2 and 4Gy) resulted in an increase in focal adhesion size and slight increases in cell migration. Src inhibition alone showed a dose dependent decrease in cell adhesion, spreading and migration and a reduction in cell survival. Radiation combined with AZD0530 showed a significant decrease in cell adhesion and migration compared to radiation alone but not to Src inhibition alone. The combination therapy showed an additive effect against clonogenic survival and in cell cycle studies radiation alone caused a G2/M cell cycle stall which was counteracted by the addition of AZD0530.Conclusion: The combination of Src inhibition with radiotherapy showed a reduction in cell migration and adhesion. However it is likely that other pathways such as Phosphatidylinositol 3-kinase (PI3K) also play a role. It is possible that combination approaches targeting interacting pathways may help to sensitise cells further and promote enhanced therapeutic response. Characterisation of the pathways involved in radiation induced motility will provide further rationale for combination therapies and provide potential for application of these therapies in the clinic.