Abstract LB-236: Preclinical efficacy of targeting FGF autocrine signaling in mesothelioma with the FGF ligand trap, FP-1039/GSK3052230

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA Fibroblast growth factor (FGF) ligand-dependent signaling plays an important role in cancer development and tumor maintenance through autocrine production of FGFs directly from cancer cells and/or through paracrine production of FGFs from the local stroma. FGF-FGFR autocrine feedback loops have been characterized in several tumor types and may also play a role in drug resistance upon exposure to chemotherapy or targeted agents. FP-1039/GSK3052230 is a ligand trap that sequesters multiple FGFs and inhibits FGF receptor signaling. We previously demonstrated that increased FGF2 mRNA levels correlated with response to GSK3052230. To further extend this hypothesis, we investigated the preclinical efficacy of this drug in models of mesothelioma, a tumor type shown to express high levels of FGF2 mRNA in cell lines and in primary tumor specimens. GSK3052230 inhibited MAPK signaling as evidenced by decreased phospho-ERK levels in both NCI-H226 and MSTO-211H cells. When both cell lines were grown as tumor xenografts in mice, GSK3052230 inhibited tumor growth in a dose-dependent manner (NCI-H226: 16 - 78% TGI; MSTO-211H: 20 - 50% TGI). However, in contrast to what was observed in cultured cells, GSK3052230 had minimal effects on phospho-ERK levels in NCI-H226 tumors. Similarly, two genes downstream of ERK known to be regulated by FGF signaling, DUSP6 and ETV4, displayed modestly reduced mRNA levels upon GSK3052230 treatment. These data demonstrate the limitation of FGF pathway downstream signaling as a pharmacodynamic (PD) readout for this drug in this study despite observing significant tumor growth inhibition. Because FGFs also play a key role in angiogenesis, we explored the effects of GSK3052230 on tumor vessel formation in NCI-H226 xenografts as a potential approach to measure PD. Dose-dependent and statistically-significant reductions in tumor vessel density were observed in GSK3052230-treated tumors compared to vehicle-treated tumors using MECA-32 endothelial cell immunohistochemical staining. These data support the clinical evaluation of this drug in mesothelioma patients. Citation Format: M. Phillip De Young, Christian Sherk, Maureen Bleam, Mary Barnette, Gopi Ganji, Bao Hoang, James Tunstead, David Bellovin, Gerrit Los, Elisabeth Minthorn, Rakesh Kumar. Preclinical efficacy of targeting FGF autocrine signaling in mesothelioma with the FGF ligand trap, FP-1039/GSK3052230. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr LB-236. doi:10.1158/1538-7445.AM2014-LB-236