Abstract 4102: Effect of HGF concentrations on c-Met inhibition investigation
Authors: Hughes Veronica S. , Siemann Dietmar W. 
Published: July 2016

Abstract
Tumor cells frequently harbor abnormalities in signaling pathways, leading to increased migration, invasion, survival, angiogenesis, and proliferation. C-Met is a receptor tyrosine kinase critical for embryogenesis and liver repair, and protein levels are often elevated in a large variety of tumors. C-Met is activated by the endogenous ligand Hepatocyte Growth Factor (HGF). HGF is produced by mesenchymal cells and stimulates the c-Met protein, leading to a variety of downstream signaling pathways that result in increased migration, proliferation, survival, and angiogenesis.
While many tumor cells express the c-Met receptor, a number of tumor types, including glioblastoma and osteosarcoma, have been observed to co-express both HGF and c-Met. The purpose of the current study was to measure tumor cell HGF secretion in vitro, to determine HGF concentrations in vivo, and study how HGF concentrations affect tumor cell response to c-Met inhibition. Over forty cell lines were investigated for HGF secretion via ELISA of conditioned media. The small molecule c-Met inhibitor BMS-777607 was used to interrupt the c-Met axis in a select number of tumor cell lines. C3H/HeJ, nude, and Balb/c mice, were measured for serum levels of HGF.
Data obtained using ELISA of conditioned media show that about one quarter of the cell lines tested secreted HGF. Cell lines tested include, but are not limited to, glioblastoma, prostate, breast, fibrosarcoma, and osteosarcoma. Migration assays were performed on several of these cell lines to determine sensitivity to BMS-777607. HGF-secreting cell lines, including the KHT, U87, U118, and OS156, are sensitive to BMS-777607 at 0.1, 1, and 10 μM. Non-HGF-secreting cell lines, such as PC-3 and MDA-MB-231, are insensitive to BMS-777607 at the same concentrations. A migration assay was performed with the PC-3 cells, with cells exposed to 0.1, 1, and 10 uM BMS-777607 while in the presence of 0, 5, 10, and 25 ng/mL HGF. These cells are not sensitive to the c-Met inhibitor at low concentrations of HGF, yet become sensitive at higher concentrations. These results indicate that sensitivity to c-Met inhibition may be dependent on both HGF-secretion status and levels of exogenous HGF. Furthermore, our findings suggest that in vitro investigations of c-Met inhibition should be done at physiologically relevant HGF concentrations.
In order to properly perform c-Met inhibition experiments in vitro, a better understanding of in situ HGF concentration is needed. Serum levels of HGF were measured in the C3H/HeJ, nude, and Balb/c mice. The average serum HGF concentration in these mice was between 3 and 5 ng/mL. Still, it is ultimately the local concentration of HGF within the tumor microenvironment that is critical, but no intra-tumor values for HGF have been reported. Consequently measurements of HGF levels within tumors by microdialysis are ongoing.
Citation Format: Veronica S. Hughes, Dietmar W. Siemann. Effect of HGF concentrations on c-Met inhibition investigation. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4102.