Analysis of transcription and protein expression changes in the 786-O human renal cell carcinoma tumor xenograft model in response to treatment with the multi-kinase inhibitor sorafenib (BAY 43-9006)

Proc Amer Assoc Cancer Res, Volume 47, 2006 906 Renal cell carcinoma (RCC) is the 6th leading cause of cancer death and is marked by a high prevalence of mutations of the VHL gene which results in the deregulation of VEGF and increased tumor angiogenesis. BAY 43-9006 (sorafenib) is an orally active, multi-kinase inhibitor that targets the serine/threonine kinase RAF (RAF-1 and B-RAF) and receptor tyrosine kinases (VEGFR-2/PDGFR-β) involved in tumor growth and angiogenesis. It is currently being evaluated in phase III clinical trials for the treatment of RCC, hepatocellular carcinoma and melanoma. In the VHL-/- 786-O tumor xenograft model, once daily oral dosing of sorafenib produces partial tumor growth inhibition at 15 mg/kg and complete tumor stasis at doses of 30 mg/kg or higher associated with inhibition of tumor microvessel formation and visible areas of tumor necrosis (Chang, YS et al. EORTC 2005). To gain a better understanding of the early gene and protein expression changes associated with tumor stasis upon treatment with sorafenib, drug and vehicle treated tumors were harvested at 4 and 24 hours after the third 60 mg/kg dose. Affymetrix GeneChip™ analysis revealed significant increases in mRNA levels of the inflammatory and angiogenic cytokines, IL-6 and IL-8, as well as the matrix metalloproteinases, MMP-1 and MMP-10 upon treatment with sorafenib. These changes were confirmed by Taqman using human mRNA specific primers. Sorafenib induced modest increases in expression of the angiogenic factor, VEGF, whereas no significant changes were observed in the mRNA levels of the angiogenic factors, FGF-1 and FGF-2, or TGF-α, a known autocrine growth factor for RCC. Measurement of protein levels of IL-6, IL-8, MMP1 and VEGF from vehicle and sorafenib-treated 786-O tumor extracts were determined by ELISA using antibodies specific for the human protein. Increases in mRNA expression in sorafenib-treated 786-O RCC tumors corresponded to increases at the protein level, which were statistically significant for IL-6, IL-8, and MMP-1. The observed changes in VEGF expression are consistent with published clinical observations of modulation of VEGF in the plasma or serum of patients treated with inhibitors targeting VEGFR. Additional studies are underway to evaluate the utility of IL-6, IL-8, and MMP-1 as pharmacodynamic biomarkers for clinical response to sorafenib.