Abstract 14: The effect of Src family kinase inhibitors in non-metastatic clear cell renal cancer.
Authors: Roseweir Antonia K. , Qayyum Tahir , Jones Robert , Oades Grenville , Aitchison Michael , Edwards Joanne 
Published: August 2014

Approximately 8000 new cases of renal cancer are diagnosed each year, with an estimated five year survival rate of 50%. Treatment options are limited, however a potential target is a family of non-receptor tyrosine kinases, called Src family kinases (SFKs). SFKs have a role in multiple oncogenic processes and are associated with promoting metastases in solid tumours; however, research in renal cancer is limited. Previously, we reported that all eight SFKs were expressed in human renal clear cell carcinoma. Lyn, Blk, Lck, Fyn and Yes showed a significant increase in expression between stages T1 and T2 and a subsequent decrease between T2 and T3, suggesting SFKs increased to promote invasion and migration for metastatic spread.

The aim of the current proposal is therefore to investigate if SFKs could be a therapeutic target for renal cancer.

The prototypical SFK, Src was investigated for association with clinical outcome measures. High membrane Src expression was associated with improved disease specific survival (p=0.097). However, low expression of phosphorylated cytoplasmic FAK at Y861 a Src specific site, was associated with poor disease specific survival (p=0.001). This suggests that poor prognosis associated with FAK is due to a family member other than Src as all SFKs can phosphorylate this residue. The effect of SFKs inhibition on migration, apoptosis and proliferation in a non-metastatic renal cancer cell line, 786O was examined. Western blot analysis demonstrated that treatment of 786O with the SFK inhibitor, dasatinib, did not affect total levels of Src, but a dose dependent reduction in SFK activation was observed, as shown via Y416 phosphorylation and FAK phosphorylation at Y861. Cells also exhibited a dose dependent reduction in migration accompanied by an increase in apoptosis when treated with dasatinib for 48 hours. However, no effect on proliferation was observed. Treatment with Src siRNA to remove Src from the cells did not significantly influence the effects observed in response to dasatinib suggesting dasatinib acts via another SFK family member.

Our data shows that activation measured via phosphorylation of the downstream marker FAK at Y861 was associated with poor prognosis and removing Src from 786O cells did not effect the actions of the Src inhibitor, dasatinib. This combined with our previous observation of SFKs expression increasing from stage T1 to T2 and decreasing from T2 to T3 lead us to conclude that SFKs are important for tumour cells migrating to the outer edge of the organ ready for metastasis then dissipate as the metastasis occurs and that this may be promoted by a SFK family member other than Src. However the specific family member responsible for these actions and the actions of dasatinib is still to be established.

Citation Format: Antonia K. Roseweir, Tahir Qayyum, Robert Jones, Grenville Oades, Michael Aitchison, Joanne Edwards. The effect of Src family kinase inhibitors in non-metastatic clear cell renal cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 14. doi:10.1158/1538-7445.AM2013-14