Abstract 1005: Ron monoclonal antibody IMC-RON8 sensitizes pancreatic cancer to histone deacetylase inhibitors.
Authors: Zou Yi , Howell Gillian M. , Brattain Lisa E. , Wang Jing , Purohit Vinee , Singh Pankaj , Brattain Michael G. 
Published: August 2014

Receptor tyrosine kinase Ron (recepteur d'origine nantais) was reported to be overexpressed in a panel of pancreatic cancer cells and in the tissue samples from pancreatic cancer patients. Increased Ron is also correlated to late stage pancreatic cancer development. Previous studies showed that Ron tyrosine kinase can be activated by its ligand macrophage stimulating protein (MSP) thereby activating oncogenic signaling pathways to promote cell survival, cell migration and invasion. Ron can also be activated by MSP-independent pathways through crosstalk with EGFR, c-Met, integrins, IGF-1R and TGFβ, which may represent a mechanism underlying drug resistance. Thus, targeting Ron kinase may represent a novel therapeutic strategy for Ron-overexpressing pancreatic cancer patients. IMC-RON8 is the first Ron specific monoclonal antibody (mAb) to enter clinical trial to target Ron overexpression. Our studies show that IMC-RON8 downmodulate Ron protein expression in Capan-1 and CFPAC-1 cells and significantly block MSP-stimulated downstream pAkt and pERk activation. IMC-RON8 also reduced cell migration as evidenced by transwell and wound healing assays. Histone deacetylase inhibitors (HDACIs) are reported to target expression of various genes through modification of the nucleosome histones and non-histone proteins. Our work shows that HDACI Panobinostat (PS) significantly decreased Ron mRNA and protein expression in pancreatic cancer cells. PS also reduced Ron tyrosine phosphorylation as measured by immunoflurecence (IF). This was associated with attenuation of downstream cell survival signaling pAkt, survivin, and XIAP. PS significantly reduced HIF1α expression. HIF1α has been reported to be the transcription factor for Ron kinase in breast cancer. HIF1α knockdown decreased Ron protein expression in pancreatic cancer cells. Overexpression of HIF1α increased Ron expression in these cells, which could be depleted by PS treatment. IMC-RON8 could sensitize pancreatic cancer cells to PS, as displayed by reduced colony formation and colony size in soft agarose assay in combination treatments with IMC-RON8 and PS compared to single treatment alone. Western blot analysis showed that Ron expression was reduced after IMC-RON8 treatment for 24 hours. A combination of IMC-RON8 and Panobinostat synergistically reduced Ron expression compared to either treatment alone. Thus, this study suggests the potential for a novel combination approach for pancreatic cancer which may ultimately be of value in treatment of pancreatic cancer.

Citation Format: Yi Zou, Gillian M. Howell, Lisa E. Brattain, Jing Wang, Vinee Purohit, Pankaj Singh, Michael G. Brattain. Ron monoclonal antibody IMC-RON8 sensitizes pancreatic cancer to histone deacetylase inhibitors. [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 1005. doi:10.1158/1538-7445.AM2013-1005