Introduction: RCC is a tumor entity with poor outcome. Targeted therapies with tyrosine kinase inhibitors (TKI) are promising agents for combating progression in RCC. We investigated the effect of the TKI sorafenib and sunitinib on cancer progression in vitro. We additionally analysed a coadministration of rottlerin, inhibiting PKCdelta, with sorafenib or sunitinib.

Methods: Four clear cell RCC cell lines were treated with sorafenib or sunitinib alone (5 μM) or in combination with rottlerin (10 μM). Proliferation (BrdU incorporation), apoptosis (caspase 3) and expression of PKCdelta in nuclei (pro-apoptitic), cytoplasm (inactive) and membranous (active) was quantified. The activity of PKCdelta was analysed by detection of phosphorylated PKCdelta (Western blot).

Results: Cell proliferation was reduced by sorafenib and rottlerin, but not by sunitinib. Combination of sorafenib and rottlerin showed an additive effect in proliferation inhibition. Rottlerin and sunitinib induced apoptosis. Althougth sorafenib alone did not induce apoptosis, in combination with rottlerin, apoptosis was more intensely induced than with rottlerin alone. All agents induced an enhanced expression of PKCdelta in the nuclei. Sunitinib in combination with rottlerin reduced membrane -bound PKCdelta. Analogue, expression of activated PKCdelta was reduced after cell treatment with sunitinib in combination with rottlerin.

Conclusion: Coadministration of sorafenib and rottlerin showed an additive effect on proliferation and apoptosis of RCC cells. The expression and activity of PKCdelta was reduced most by sorafenib in comibation with rottlerin. This indicates an improvement in RCC therapy with sorafenib by coadministration of rottlerin.

Citation Format: Matthias W. Joeckel, Elke Schneider, Frederik C. Roos, Christian Hampel, Joachim W. Thueroff, Walburgis Brenner. Sorafenib in combination with rottlerin show an additive effects in renal cell carcinoma (RCC) cells. [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 1041. doi:10.1158/1538-7445.AM2013-1041